From a6607930b6cd829fc7f680b48a937d827e0bb931 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:54 -0500
Subject: kernfs: make kernfs_deactivate() honor KERNFS_LOCKDEP flag
kernfs_deactivate() forgot to check whether KERNFS_LOCKDEP is set
before performing lockdep annotations and ends up feeding
uninitialized lockdep_map to lockdep triggering warning like the
following on USB stick hotunplug.
usb 1-2: USB disconnect, device number 2
INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 62 Comm: khubd Not tainted 3.13.0-work+ #82
Hardware name: empty empty/S3992, BIOS 080011 10/26/2007
ffff880065ca7f60 ffff88013a4ffa08 ffffffff81cfb6bd 0000000000000002
ffff88013a4ffac8 ffffffff810f8530 ffff88013a4fc710 0000000000000002
ffff880100000000 ffffffff82a3db50 0000000000000001 ffff88013a4fc710
Call Trace:
[<ffffffff81cfb6bd>] dump_stack+0x4e/0x7a
[<ffffffff810f8530>] __lock_acquire+0x1910/0x1e70
[<ffffffff810f931a>] lock_acquire+0x9a/0x1d0
[<ffffffff8127c75e>] kernfs_deactivate+0xee/0x130
[<ffffffff8127d4c8>] kernfs_addrm_finish+0x38/0x60
[<ffffffff8127d701>] kernfs_remove_by_name_ns+0x51/0xa0
[<ffffffff8127b4f1>] remove_files.isra.1+0x41/0x80
[<ffffffff8127b7e7>] sysfs_remove_group+0x47/0xa0
[<ffffffff8127b873>] sysfs_remove_groups+0x33/0x50
[<ffffffff8177d66d>] device_remove_attrs+0x4d/0x80
[<ffffffff8177e25e>] device_del+0x12e/0x1d0
[<ffffffff819722c2>] usb_disconnect+0x122/0x1a0
[<ffffffff819749b5>] hub_thread+0x3c5/0x1290
[<ffffffff810c6a6d>] kthread+0xed/0x110
[<ffffffff81d0a56c>] ret_from_fork+0x7c/0xb0
Fix it by making kernfs_deactivate() perform lockdep annotations only
if KERNFS_LOCKDEP is set.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 5104cf5d25c5..bd6e18be6e1a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -187,19 +187,23 @@ static void kernfs_deactivate(struct kernfs_node *kn)
kn->u.completion = (void *)&wait;
- rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ if (kn->flags & KERNFS_LOCKDEP)
+ rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
/* atomic_add_return() is a mb(), put_active() will always see
* the updated kn->u.completion.
*/
v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
if (v != KN_DEACTIVATED_BIAS) {
- lock_contended(&kn->dep_map, _RET_IP_);
+ if (kn->flags & KERNFS_LOCKDEP)
+ lock_contended(&kn->dep_map, _RET_IP_);
wait_for_completion(&wait);
}
- lock_acquired(&kn->dep_map, _RET_IP_);
- rwsem_release(&kn->dep_map, 1, _RET_IP_);
+ if (kn->flags & KERNFS_LOCKDEP) {
+ lock_acquired(&kn->dep_map, _RET_IP_);
+ rwsem_release(&kn->dep_map, 1, _RET_IP_);
+ }
}
/**
--
cgit v1.2.3
From abd54f028ec30976d6e797e7474ec91d96186a0c Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:55 -0500
Subject: kernfs: replace kernfs_node->u.completion with
kernfs_root->deactivate_waitq
kernfs_node->u.completion is used to notify deactivation completion
from kernfs_put_active() to kernfs_deactivate(). We now allow
multiple racing removals of the same node and the current removal
scheme is no longer correct - kernfs_remove() invocation may return
before the node is properly deactivated if it races against another
removal. The removal path will be restructured to address the issue.
To help such restructure which requires supporting multiple waiters,
this patch replaces kernfs_node->u.completion with
kernfs_root->deactivate_waitq. This makes deactivation event
notifications share a per-root waitqueue_head; however, the wait path
is quite cold and this will also allow shaving one pointer off
kernfs_node.
v2: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
KERNFS_LOCKDEP flag").
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 31 +++++++++++++------------------
include/linux/kernfs.h | 4 ++--
2 files changed, 15 insertions(+), 20 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index bd6e18be6e1a..2193d30156ef 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -8,6 +8,7 @@
* This file is released under the GPLv2.
*/
+#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/idr.h>
@@ -151,6 +152,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
*/
void kernfs_put_active(struct kernfs_node *kn)
{
+ struct kernfs_root *root = kernfs_root(kn);
int v;
if (unlikely(!kn))
@@ -162,11 +164,7 @@ void kernfs_put_active(struct kernfs_node *kn)
if (likely(v != KN_DEACTIVATED_BIAS))
return;
- /*
- * atomic_dec_return() is a mb(), we'll always see the updated
- * kn->u.completion.
- */
- complete(kn->u.completion);
+ wake_up_all(&root->deactivate_waitq);
}
/**
@@ -177,28 +175,24 @@ void kernfs_put_active(struct kernfs_node *kn)
*/
static void kernfs_deactivate(struct kernfs_node *kn)
{
- DECLARE_COMPLETION_ONSTACK(wait);
- int v;
+ struct kernfs_root *root = kernfs_root(kn);
BUG_ON(!(kn->flags & KERNFS_REMOVED));
if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
return;
- kn->u.completion = (void *)&wait;
-
if (kn->flags & KERNFS_LOCKDEP)
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
- /* atomic_add_return() is a mb(), put_active() will always see
- * the updated kn->u.completion.
- */
- v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
- if (v != KN_DEACTIVATED_BIAS) {
- if (kn->flags & KERNFS_LOCKDEP)
- lock_contended(&kn->dep_map, _RET_IP_);
- wait_for_completion(&wait);
- }
+ atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
+
+ if ((kn->flags & KERNFS_LOCKDEP) &&
+ atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+ lock_contended(&kn->dep_map, _RET_IP_);
+
+ wait_event(root->deactivate_waitq,
+ atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
if (kn->flags & KERNFS_LOCKDEP) {
lock_acquired(&kn->dep_map, _RET_IP_);
@@ -630,6 +624,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
root->dir_ops = kdops;
root->kn = kn;
+ init_waitqueue_head(&root->deactivate_waitq);
return root;
}
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5be9f0228a3b..295a3bf642ba 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -15,7 +15,7 @@
#include <linux/lockdep.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
-#include <linux/completion.h>
+#include <linux/wait.h>
struct file;
struct dentry;
@@ -92,7 +92,6 @@ struct kernfs_node {
struct rb_node rb;
union {
- struct completion *completion;
struct kernfs_node *removed_list;
} u;
@@ -133,6 +132,7 @@ struct kernfs_root {
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
struct kernfs_dir_ops *dir_ops;
+ wait_queue_head_t deactivate_waitq;
};
struct kernfs_open_file {
--
cgit v1.2.3
From 35beab0635f3cdd475e3c11a304b866c25b76fcf Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:56 -0500
Subject: kernfs: restructure removal path to fix possible premature return
The recursive nature of kernfs_remove() means that, even if
kernfs_remove() is not allowed to be called multiple times on the same
node, there may be race conditions between removal of parent and its
descendants. While we can claim that kernfs_remove() shouldn't be
called on one of the descendants while the removal of an ancestor is
in progress, such rule is unnecessarily restrictive and very difficult
to enforce. It's better to simply allow invoking kernfs_remove() as
the caller sees fit as long as the caller ensures that the node is
accessible.
The current behavior in such situations is broken. Whoever enters
removal path first takes the node off the hierarchy and then
deactivates. Following removers either return as soon as it notices
that it's not the first one or can't even find the target node as it
has already been removed from the hierarchy. In both cases, the
following removers may finish prematurely while the nodes which should
be removed and drained are still being processed by the first one.
This patch restructures so that multiple removers, whether through
recursion or direction invocation, always follow the following rules.
* When there are multiple concurrent removers, only one puts the base
ref.
* Regardless of which one puts the base ref, all removers are blocked
until the target node is fully deactivated and removed.
To achieve the above, removal path now first marks all descendants
including self REMOVED and then deactivates and unlinks leftmost
descendant one-by-one. kernfs_deactivate() is called directly from
__kernfs_removal() and drops and regrabs kernfs_mutex for each
descendant to drain active refs. As this means that multiple removers
can enter kernfs_deactivate() for the same node, the function is
updated so that it can handle multiple deactivators of the same node -
only one actually deactivates but all wait till drain completion.
The restructured removal path guarantees that a removed node gets
unlinked only after the node is deactivated and drained. Combined
with proper multiple deactivator handling, this guarantees that any
invocation of kernfs_remove() returns only after the node itself and
all its descendants are deactivated, drained and removed.
v2: Draining separated into a separate loop (used to be in the same
loop as unlink) and done from __kernfs_deactivate(). This is to
allow exposing deactivation as a separate interface later.
Root node removal was broken in v1 patch. Fixed.
v3: Revert most of v2 except for root node removal fix and
simplification of KERNFS_REMOVED setting loop.
v4: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
KERNFS_LOCKDEP flag").
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 129 +++++++++++++++++++++++++++++---------------------------
1 file changed, 68 insertions(+), 61 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 2193d30156ef..3ac93737174a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -106,18 +106,24 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
* kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree
* @kn: kernfs_node of interest
*
- * Unlink @kn from its sibling rbtree which starts from
- * kn->parent->dir.children.
+ * Try to unlink @kn from its sibling rbtree which starts from
+ * kn->parent->dir.children. Returns %true if @kn was actually
+ * removed, %false if @kn wasn't on the rbtree.
*
* Locking:
* mutex_lock(kernfs_mutex)
*/
-static void kernfs_unlink_sibling(struct kernfs_node *kn)
+static bool kernfs_unlink_sibling(struct kernfs_node *kn)
{
+ if (RB_EMPTY_NODE(&kn->rb))
+ return false;
+
if (kernfs_type(kn) == KERNFS_DIR)
kn->parent->dir.subdirs--;
rb_erase(&kn->rb, &kn->parent->dir.children);
+ RB_CLEAR_NODE(&kn->rb);
+ return true;
}
/**
@@ -171,26 +177,34 @@ void kernfs_put_active(struct kernfs_node *kn)
* kernfs_deactivate - deactivate kernfs_node
* @kn: kernfs_node to deactivate
*
- * Deny new active references and drain existing ones.
+ * Deny new active references and drain existing ones. Mutiple
+ * removers may invoke this function concurrently on @kn and all will
+ * return after deactivation and draining are complete.
*/
static void kernfs_deactivate(struct kernfs_node *kn)
+ __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
{
struct kernfs_root *root = kernfs_root(kn);
+ lockdep_assert_held(&kernfs_mutex);
BUG_ON(!(kn->flags & KERNFS_REMOVED));
if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
return;
- if (kn->flags & KERNFS_LOCKDEP)
- rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ /* only the first invocation on @kn should deactivate it */
+ if (atomic_read(&kn->active) >= 0)
+ atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
- atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
+ mutex_unlock(&kernfs_mutex);
- if ((kn->flags & KERNFS_LOCKDEP) &&
- atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
- lock_contended(&kn->dep_map, _RET_IP_);
+ if (kn->flags & KERNFS_LOCKDEP) {
+ rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+ lock_contended(&kn->dep_map, _RET_IP_);
+ }
+ /* but everyone should wait for draining */
wait_event(root->deactivate_waitq,
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
@@ -198,6 +212,8 @@ static void kernfs_deactivate(struct kernfs_node *kn)
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
+
+ mutex_lock(&kernfs_mutex);
}
/**
@@ -347,6 +363,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
atomic_set(&kn->count, 1);
atomic_set(&kn->active, 0);
+ RB_CLEAR_NODE(&kn->rb);
kn->name = name;
kn->mode = mode;
@@ -453,49 +470,6 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
return 0;
}
-/**
- * kernfs_remove_one - remove kernfs_node from parent
- * @acxt: addrm context to use
- * @kn: kernfs_node to be removed
- *
- * Mark @kn removed and drop nlink of parent inode if @kn is a
- * directory. @kn is unlinked from the children list.
- *
- * This function should be called between calls to
- * kernfs_addrm_start() and kernfs_addrm_finish() and should be
- * passed the same @acxt as passed to kernfs_addrm_start().
- *
- * LOCKING:
- * Determined by kernfs_addrm_start().
- */
-static void kernfs_remove_one(struct kernfs_addrm_cxt *acxt,
- struct kernfs_node *kn)
-{
- struct kernfs_iattrs *ps_iattr;
-
- /*
- * Removal can be called multiple times on the same node. Only the
- * first invocation is effective and puts the base ref.
- */
- if (kn->flags & KERNFS_REMOVED)
- return;
-
- if (kn->parent) {
- kernfs_unlink_sibling(kn);
-
- /* Update timestamps on the parent */
- ps_iattr = kn->parent->iattr;
- if (ps_iattr) {
- ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
- ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
- }
- }
-
- kn->flags |= KERNFS_REMOVED;
- kn->u.removed_list = acxt->removed;
- acxt->removed = kn;
-}
-
/**
* kernfs_addrm_finish - finish up kernfs_node add/remove
* @acxt: addrm context to finish up
@@ -519,7 +493,6 @@ void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
acxt->removed = kn->u.removed_list;
- kernfs_deactivate(kn);
kernfs_unmap_bin_file(kn);
kernfs_put(kn);
}
@@ -828,20 +801,54 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
struct kernfs_node *kn)
{
- struct kernfs_node *pos, *next;
+ struct kernfs_node *pos;
+
+ lockdep_assert_held(&kernfs_mutex);
if (!kn)
return;
pr_debug("kernfs %s: removing\n", kn->name);
- next = NULL;
+ /* disable lookup and node creation under @kn */
+ pos = NULL;
+ while ((pos = kernfs_next_descendant_post(pos, kn)))
+ pos->flags |= KERNFS_REMOVED;
+
+ /* deactivate and unlink the subtree node-by-node */
do {
- pos = next;
- next = kernfs_next_descendant_post(pos, kn);
- if (pos)
- kernfs_remove_one(acxt, pos);
- } while (next);
+ pos = kernfs_leftmost_descendant(kn);
+
+ /*
+ * kernfs_deactivate() drops kernfs_mutex temporarily and
+ * @pos's base ref could have been put by someone else by
+ * the time the function returns. Make sure it doesn't go
+ * away underneath us.
+ */
+ kernfs_get(pos);
+
+ kernfs_deactivate(pos);
+
+ /*
+ * kernfs_unlink_sibling() succeeds once per node. Use it
+ * to decide who's responsible for cleanups.
+ */
+ if (!pos->parent || kernfs_unlink_sibling(pos)) {
+ struct kernfs_iattrs *ps_iattr =
+ pos->parent ? pos->parent->iattr : NULL;
+
+ /* update timestamps on the parent */
+ if (ps_iattr) {
+ ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
+ ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
+ }
+
+ pos->u.removed_list = acxt->removed;
+ acxt->removed = pos;
+ }
+
+ kernfs_put(pos);
+ } while (pos != kn);
}
/**
--
cgit v1.2.3
From ccf02aaf8167bb8bfb3c17c01c843d309b872671 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:57 -0500
Subject: kernfs: invoke kernfs_unmap_bin_file() directly from
kernfs_deactivate()
kernfs_unmap_bin_file() is supposed to unmap all memory mappings of
the target file before kernfs_remove() finishes; however, it currently
is being called from kernfs_addrm_finish() and has the same race
problem as the original implementation of deactivation when there are
multiple removers - only the remover which snatches the node to its
addrm_cxt->removed list is guaranteed to wait for its completion
before returning.
It can be easily fixed by moving kernfs_unmap_bin_file() invocation
from kernfs_addrm_finish() to kernfs_deactivated(). The function may
be called multiple times but that shouldn't do any harm.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 3ac93737174a..9603c06550a0 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -177,9 +177,10 @@ void kernfs_put_active(struct kernfs_node *kn)
* kernfs_deactivate - deactivate kernfs_node
* @kn: kernfs_node to deactivate
*
- * Deny new active references and drain existing ones. Mutiple
- * removers may invoke this function concurrently on @kn and all will
- * return after deactivation and draining are complete.
+ * Deny new active references, drain existing ones and nuke all
+ * existing mmaps. Mutiple removers may invoke this function
+ * concurrently on @kn and all will return after deactivation and
+ * draining are complete.
*/
static void kernfs_deactivate(struct kernfs_node *kn)
__releases(&kernfs_mutex) __acquires(&kernfs_mutex)
@@ -213,6 +214,8 @@ static void kernfs_deactivate(struct kernfs_node *kn)
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
+ kernfs_unmap_bin_file(kn);
+
mutex_lock(&kernfs_mutex);
}
@@ -493,7 +496,6 @@ void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
acxt->removed = kn->u.removed_list;
- kernfs_unmap_bin_file(kn);
kernfs_put(kn);
}
}
--
cgit v1.2.3
From 988cd7afb3f37598891ca70b4c6eb914c338c46a Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:58 -0500
Subject: kernfs: remove kernfs_addrm_cxt
kernfs_addrm_cxt and the accompanying kernfs_addrm_start/finish() were
added because there were operations which should be performed outside
kernfs_mutex after adding and removing kernfs_nodes. The necessary
operations were recorded in kernfs_addrm_cxt and performed by
kernfs_addrm_finish(); however, after the recent changes which
relocated deactivation and unmapping so that they're performed
directly during removal, the only operation kernfs_addrm_finish()
performs is kernfs_put(), which can be moved inside the removal path
too.
This patch moves the kernfs_put() of the base ref to __kernfs_remove()
and remove kernfs_addrm_cxt and kernfs_addrm_start/finish().
* kernfs_add_one() is updated to grab and release kernfs_mutex itself.
sysfs_addrm_start/finish() invocations around it are removed from
all users.
* __kernfs_remove() puts an unlinked node directly instead of chaining
it to kernfs_addrm_cxt. Its callers are updated to grab and release
kernfs_mutex instead of calling kernfs_addrm_start/finish() around
it.
v2: Rebased on top of "kernfs: associate a new kernfs_node with its
parent on creation" which dropped @parent from kernfs_add_one().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 109 ++++++++++----------------------------------
fs/kernfs/file.c | 6 +--
fs/kernfs/kernfs-internal.h | 11 +----
fs/kernfs/symlink.c | 6 +--
include/linux/kernfs.h | 4 --
5 files changed, 28 insertions(+), 108 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 9603c06550a0..948551d222b4 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -395,70 +395,45 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
return kn;
}
-/**
- * kernfs_addrm_start - prepare for kernfs_node add/remove
- * @acxt: pointer to kernfs_addrm_cxt to be used
- *
- * This function is called when the caller is about to add or remove
- * kernfs_node. This function acquires kernfs_mutex. @acxt is used
- * to keep and pass context to other addrm functions.
- *
- * LOCKING:
- * Kernel thread context (may sleep). kernfs_mutex is locked on
- * return.
- */
-void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
- __acquires(kernfs_mutex)
-{
- memset(acxt, 0, sizeof(*acxt));
-
- mutex_lock(&kernfs_mutex);
-}
-
/**
* kernfs_add_one - add kernfs_node to parent without warning
- * @acxt: addrm context to use
* @kn: kernfs_node to be added
*
* The caller must already have initialized @kn->parent. This
* function increments nlink of the parent's inode if @kn is a
* directory and link into the children list of the parent.
*
- * This function should be called between calls to
- * kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
- * the same @acxt as passed to kernfs_addrm_start().
- *
- * LOCKING:
- * Determined by kernfs_addrm_start().
- *
* RETURNS:
* 0 on success, -EEXIST if entry with the given name already
* exists.
*/
-int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
+int kernfs_add_one(struct kernfs_node *kn)
{
struct kernfs_node *parent = kn->parent;
- bool has_ns = kernfs_ns_enabled(parent);
struct kernfs_iattrs *ps_iattr;
+ bool has_ns;
int ret;
- if (has_ns != (bool)kn->ns) {
- WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
- has_ns ? "required" : "invalid", parent->name, kn->name);
- return -EINVAL;
- }
+ mutex_lock(&kernfs_mutex);
+
+ ret = -EINVAL;
+ has_ns = kernfs_ns_enabled(parent);
+ if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
+ has_ns ? "required" : "invalid", parent->name, kn->name))
+ goto out_unlock;
if (kernfs_type(parent) != KERNFS_DIR)
- return -EINVAL;
+ goto out_unlock;
+ ret = -ENOENT;
if (parent->flags & KERNFS_REMOVED)
- return -ENOENT;
+ goto out_unlock;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
ret = kernfs_link_sibling(kn);
if (ret)
- return ret;
+ goto out_unlock;
/* Update timestamps on the parent */
ps_iattr = parent->iattr;
@@ -469,35 +444,10 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
/* Mark the entry added into directory tree */
kn->flags &= ~KERNFS_REMOVED;
-
- return 0;
-}
-
-/**
- * kernfs_addrm_finish - finish up kernfs_node add/remove
- * @acxt: addrm context to finish up
- *
- * Finish up kernfs_node add/remove. Resources acquired by
- * kernfs_addrm_start() are released and removed kernfs_nodes are
- * cleaned up.
- *
- * LOCKING:
- * kernfs_mutex is released.
- */
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
- __releases(kernfs_mutex)
-{
- /* release resources acquired by kernfs_addrm_start() */
+ ret = 0;
+out_unlock:
mutex_unlock(&kernfs_mutex);
-
- /* kill removed kernfs_nodes */
- while (acxt->removed) {
- struct kernfs_node *kn = acxt->removed;
-
- acxt->removed = kn->u.removed_list;
-
- kernfs_put(kn);
- }
+ return ret;
}
/**
@@ -630,7 +580,6 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
const char *name, umode_t mode,
void *priv, const void *ns)
{
- struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
int rc;
@@ -644,10 +593,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
kn->priv = priv;
/* link in */
- kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn);
- kernfs_addrm_finish(&acxt);
-
+ rc = kernfs_add_one(kn);
if (!rc)
return kn;
@@ -800,8 +746,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
return pos->parent;
}
-static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
- struct kernfs_node *kn)
+static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;
@@ -845,8 +790,7 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
}
- pos->u.removed_list = acxt->removed;
- acxt->removed = pos;
+ kernfs_put(pos);
}
kernfs_put(pos);
@@ -861,11 +805,9 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
*/
void kernfs_remove(struct kernfs_node *kn)
{
- struct kernfs_addrm_cxt acxt;
-
- kernfs_addrm_start(&acxt);
- __kernfs_remove(&acxt, kn);
- kernfs_addrm_finish(&acxt);
+ mutex_lock(&kernfs_mutex);
+ __kernfs_remove(kn);
+ mutex_unlock(&kernfs_mutex);
}
/**
@@ -880,7 +822,6 @@ void kernfs_remove(struct kernfs_node *kn)
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{
- struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
if (!parent) {
@@ -889,13 +830,13 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
return -ENOENT;
}
- kernfs_addrm_start(&acxt);
+ mutex_lock(&kernfs_mutex);
kn = kernfs_find_ns(parent, name, ns);
if (kn)
- __kernfs_remove(&acxt, kn);
+ __kernfs_remove(kn);
- kernfs_addrm_finish(&acxt);
+ mutex_unlock(&kernfs_mutex);
if (kn)
return 0;
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index dbf397bfdff2..10a8c91c49d6 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -820,7 +820,6 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
bool name_is_static,
struct lock_class_key *key)
{
- struct kernfs_addrm_cxt acxt;
struct kernfs_node *kn;
unsigned flags;
int rc;
@@ -855,10 +854,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
if (ops->mmap)
kn->flags |= KERNFS_HAS_MMAP;
- kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn);
- kernfs_addrm_finish(&acxt);
-
+ rc = kernfs_add_one(kn);
if (rc) {
kernfs_put(kn);
return ERR_PTR(rc);
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index eb536b76374a..46b58de794d6 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -44,13 +44,6 @@ static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
return kn->dir.root;
}
-/*
- * Context structure to be used while adding/removing nodes.
- */
-struct kernfs_addrm_cxt {
- struct kernfs_node *removed;
-};
-
/*
* mount.c
*/
@@ -100,9 +93,7 @@ extern const struct inode_operations kernfs_dir_iops;
struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
void kernfs_put_active(struct kernfs_node *kn);
-void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt);
-int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn);
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt);
+int kernfs_add_one(struct kernfs_node *kn);
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
const char *name, umode_t mode,
unsigned flags);
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 4d457055acb9..8a198898e39a 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -27,7 +27,6 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
struct kernfs_node *target)
{
struct kernfs_node *kn;
- struct kernfs_addrm_cxt acxt;
int error;
kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK);
@@ -39,10 +38,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
kn->symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */
- kernfs_addrm_start(&acxt);
- error = kernfs_add_one(&acxt, kn);
- kernfs_addrm_finish(&acxt);
-
+ error = kernfs_add_one(kn);
if (!error)
return kn;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 295a3bf642ba..38646f6096bc 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -91,10 +91,6 @@ struct kernfs_node {
struct rb_node rb;
- union {
- struct kernfs_node *removed_list;
- } u;
-
const void *ns; /* namespace tag */
unsigned int hash; /* ns + name hash */
union {
--
cgit v1.2.3
From 182fd64b66342219d6fcf2b84d337529d120d95c Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:02:59 -0500
Subject: kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()
There currently are two mechanisms gating active ref lockdep
annotations - KERNFS_LOCKDEP flag and KERNFS_ACTIVE_REF type mask.
The former disables lockdep annotations in kernfs_get/put_active()
while the latter disables all of kernfs_deactivate().
While KERNFS_ACTIVE_REF also behaves as an optimization to skip the
deactivation step for non-file nodes, the benefit is marginal and it
needlessly diverges code paths. Let's drop KERNFS_ACTIVE_REF.
While at it, add a test helper kernfs_lockdep() to test KERNFS_LOCKDEP
flag so that it's more convenient and the related code can be compiled
out when not enabled.
v2: Refreshed on top of ("kernfs: make kernfs_deactivate() honor
KERNFS_LOCKDEP flag"). As the earlier patch already added
KERNFS_LOCKDEP tests to kernfs_deactivate(), those additions are
dropped from this patch and the existing ones are simply converted
to kernfs_lockdep().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 20 +++++++++++++-------
include/linux/kernfs.h | 1 -
2 files changed, 13 insertions(+), 8 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 948551d222b4..5cf137b63db9 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -22,6 +22,15 @@ DEFINE_MUTEX(kernfs_mutex);
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
+static bool kernfs_lockdep(struct kernfs_node *kn)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ return kn->flags & KERNFS_LOCKDEP;
+#else
+ return false;
+#endif
+}
+
/**
* kernfs_name_hash
* @name: Null terminated string to hash
@@ -144,7 +153,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
if (!atomic_inc_unless_negative(&kn->active))
return NULL;
- if (kn->flags & KERNFS_LOCKDEP)
+ if (kernfs_lockdep(kn))
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
return kn;
}
@@ -164,7 +173,7 @@ void kernfs_put_active(struct kernfs_node *kn)
if (unlikely(!kn))
return;
- if (kn->flags & KERNFS_LOCKDEP)
+ if (kernfs_lockdep(kn))
rwsem_release(&kn->dep_map, 1, _RET_IP_);
v = atomic_dec_return(&kn->active);
if (likely(v != KN_DEACTIVATED_BIAS))
@@ -190,16 +199,13 @@ static void kernfs_deactivate(struct kernfs_node *kn)
lockdep_assert_held(&kernfs_mutex);
BUG_ON(!(kn->flags & KERNFS_REMOVED));
- if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
- return;
-
/* only the first invocation on @kn should deactivate it */
if (atomic_read(&kn->active) >= 0)
atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
mutex_unlock(&kernfs_mutex);
- if (kn->flags & KERNFS_LOCKDEP) {
+ if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_);
@@ -209,7 +215,7 @@ static void kernfs_deactivate(struct kernfs_node *kn)
wait_event(root->deactivate_waitq,
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
- if (kn->flags & KERNFS_LOCKDEP) {
+ if (kernfs_lockdep(kn)) {
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 38646f6096bc..dc4cd6c04236 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -35,7 +35,6 @@ enum kernfs_node_type {
};
#define KERNFS_TYPE_MASK 0x000f
-#define KERNFS_ACTIVE_REF KERNFS_FILE
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {
--
cgit v1.2.3
From 81c173cb5e87fbb47ccd80630faefe39bbf68449 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:03:00 -0500
Subject: kernfs: remove KERNFS_REMOVED
KERNFS_REMOVED is used to mark half-initialized and dying nodes so
that they don't show up in lookups and deny adding new nodes under or
renaming it; however, its role overlaps that of deactivation.
It's necessary to deny addition of new children while removal is in
progress; however, this role considerably intersects with deactivation
- KERNFS_REMOVED prevents new children while deactivation prevents new
file operations. There's no reason to have them separate making
things more complex than necessary.
This patch removes KERNFS_REMOVED.
* Instead of KERNFS_REMOVED, each node now starts its life
deactivated. This means that we now use both atomic_add() and
atomic_sub() on KN_DEACTIVATED_BIAS, which is INT_MIN. The compiler
generates an overflow warnings when negating INT_MIN as the negation
can't be represented as a positive number. Nothing is actually
broken but let's bump BIAS by one to avoid the warnings for archs
which negates the subtrahend..
* A new helper kernfs_active() which tests whether kn->active >= 0 is
added for convenience and lockdep annotation. All KERNFS_REMOVED
tests are replaced with negated kernfs_active() tests.
* __kernfs_remove() is updated to deactivate, but not drain, all nodes
in the subtree instead of setting KERNFS_REMOVED. This removes
deactivation from kernfs_deactivate(), which is now renamed to
kernfs_drain().
* Sanity check on KERNFS_REMOVED in kernfs_put() is replaced with
checks on the active ref.
* Some comment style updates in the affected area.
v2: Reordered before removal path restructuring. kernfs_active()
dropped and kernfs_get/put_active() used instead. RB_EMPTY_NODE()
used in the lookup paths.
v3: Reverted most of v2 except for creating a new node with
KN_DEACTIVATED_BIAS.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 66 ++++++++++++++++++++++++---------------------
fs/kernfs/kernfs-internal.h | 3 ++-
include/linux/kernfs.h | 1 -
3 files changed, 37 insertions(+), 33 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 5cf137b63db9..d0fd739bf82d 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -22,6 +22,12 @@ DEFINE_MUTEX(kernfs_mutex);
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
+static bool kernfs_active(struct kernfs_node *kn)
+{
+ lockdep_assert_held(&kernfs_mutex);
+ return atomic_read(&kn->active) >= 0;
+}
+
static bool kernfs_lockdep(struct kernfs_node *kn)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -183,25 +189,20 @@ void kernfs_put_active(struct kernfs_node *kn)
}
/**
- * kernfs_deactivate - deactivate kernfs_node
- * @kn: kernfs_node to deactivate
+ * kernfs_drain - drain kernfs_node
+ * @kn: kernfs_node to drain
*
- * Deny new active references, drain existing ones and nuke all
- * existing mmaps. Mutiple removers may invoke this function
- * concurrently on @kn and all will return after deactivation and
- * draining are complete.
+ * Drain existing usages and nuke all existing mmaps of @kn. Mutiple
+ * removers may invoke this function concurrently on @kn and all will
+ * return after draining is complete.
*/
-static void kernfs_deactivate(struct kernfs_node *kn)
+static void kernfs_drain(struct kernfs_node *kn)
__releases(&kernfs_mutex) __acquires(&kernfs_mutex)
{
struct kernfs_root *root = kernfs_root(kn);
lockdep_assert_held(&kernfs_mutex);
- BUG_ON(!(kn->flags & KERNFS_REMOVED));
-
- /* only the first invocation on @kn should deactivate it */
- if (atomic_read(&kn->active) >= 0)
- atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
+ WARN_ON_ONCE(kernfs_active(kn));
mutex_unlock(&kernfs_mutex);
@@ -253,13 +254,15 @@ void kernfs_put(struct kernfs_node *kn)
return;
root = kernfs_root(kn);
repeat:
- /* Moving/renaming is always done while holding reference.
+ /*
+ * Moving/renaming is always done while holding reference.
* kn->parent won't change beneath us.
*/
parent = kn->parent;
- WARN(!(kn->flags & KERNFS_REMOVED), "kernfs: free using entry: %s/%s\n",
- parent ? parent->name : "", kn->name);
+ WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS,
+ "kernfs_put: %s/%s: released with incorrect active_ref %d\n",
+ parent ? parent->name : "", kn->name, atomic_read(&kn->active));
if (kernfs_type(kn) == KERNFS_LINK)
kernfs_put(kn->symlink.target_kn);
@@ -301,8 +304,8 @@ static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
kn = dentry->d_fsdata;
mutex_lock(&kernfs_mutex);
- /* The kernfs node has been deleted */
- if (kn->flags & KERNFS_REMOVED)
+ /* The kernfs node has been deactivated */
+ if (!kernfs_active(kn))
goto out_bad;
/* The kernfs node has been moved? */
@@ -371,12 +374,12 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
kn->ino = ret;
atomic_set(&kn->count, 1);
- atomic_set(&kn->active, 0);
+ atomic_set(&kn->active, KN_DEACTIVATED_BIAS);
RB_CLEAR_NODE(&kn->rb);
kn->name = name;
kn->mode = mode;
- kn->flags = flags | KERNFS_REMOVED;
+ kn->flags = flags;
return kn;
@@ -432,7 +435,7 @@ int kernfs_add_one(struct kernfs_node *kn)
goto out_unlock;
ret = -ENOENT;
- if (parent->flags & KERNFS_REMOVED)
+ if (!kernfs_active(parent))
goto out_unlock;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
@@ -449,7 +452,7 @@ int kernfs_add_one(struct kernfs_node *kn)
}
/* Mark the entry added into directory tree */
- kn->flags &= ~KERNFS_REMOVED;
+ atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
ret = 0;
out_unlock:
mutex_unlock(&kernfs_mutex);
@@ -549,7 +552,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
return ERR_PTR(-ENOMEM);
}
- kn->flags &= ~KERNFS_REMOVED;
+ atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
kn->priv = priv;
kn->dir.root = root;
@@ -763,24 +766,25 @@ static void __kernfs_remove(struct kernfs_node *kn)
pr_debug("kernfs %s: removing\n", kn->name);
- /* disable lookup and node creation under @kn */
+ /* prevent any new usage under @kn by deactivating all nodes */
pos = NULL;
while ((pos = kernfs_next_descendant_post(pos, kn)))
- pos->flags |= KERNFS_REMOVED;
+ if (kernfs_active(pos))
+ atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
/* deactivate and unlink the subtree node-by-node */
do {
pos = kernfs_leftmost_descendant(kn);
/*
- * kernfs_deactivate() drops kernfs_mutex temporarily and
- * @pos's base ref could have been put by someone else by
- * the time the function returns. Make sure it doesn't go
- * away underneath us.
+ * kernfs_drain() drops kernfs_mutex temporarily and @pos's
+ * base ref could have been put by someone else by the time
+ * the function returns. Make sure it doesn't go away
+ * underneath us.
*/
kernfs_get(pos);
- kernfs_deactivate(pos);
+ kernfs_drain(pos);
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
@@ -865,7 +869,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
mutex_lock(&kernfs_mutex);
error = -ENOENT;
- if ((kn->flags | new_parent->flags) & KERNFS_REMOVED)
+ if (!kernfs_active(kn) || !kernfs_active(new_parent))
goto out;
error = 0;
@@ -925,7 +929,7 @@ static struct kernfs_node *kernfs_dir_pos(const void *ns,
struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
{
if (pos) {
- int valid = !(pos->flags & KERNFS_REMOVED) &&
+ int valid = kernfs_active(pos) &&
pos->parent == parent && hash == pos->hash;
kernfs_put(pos);
if (!valid)
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 46b58de794d6..a91d7a1113d9 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -26,7 +26,8 @@ struct kernfs_iattrs {
struct simple_xattrs xattrs;
};
-#define KN_DEACTIVATED_BIAS INT_MIN
+/* +1 to avoid triggering overflow warning when negating it */
+#define KN_DEACTIVATED_BIAS (INT_MIN + 1)
/* KERNFS_TYPE_MASK and types are defined in include/linux/kernfs.h */
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index dc4cd6c04236..917bc6c1eb04 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -38,7 +38,6 @@ enum kernfs_node_type {
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {
- KERNFS_REMOVED = 0x0010,
KERNFS_NS = 0x0020,
KERNFS_HAS_SEQ_SHOW = 0x0040,
KERNFS_HAS_MMAP = 0x0080,
--
cgit v1.2.3
From 6b0afc2a21726b2d6b6aa441af40cafaf5405cc8 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:03:01 -0500
Subject: kernfs, sysfs, driver-core: implement kernfs_remove_self() and its
wrappers
Sometimes it's necessary to implement a node which wants to delete
nodes including itself. This isn't straightforward because of kernfs
active reference. While a file operation is in progress, an active
reference is held and kernfs_remove() waits for all such references to
drain before completing. For a self-deleting node, this is a deadlock
as kernfs_remove() ends up waiting for an active reference that itself
is sitting on top of.
This currently is worked around in the sysfs layer using
sysfs_schedule_callback() which makes such removals asynchronous.
While it works, it's rather cumbersome and inherently breaks
synchronicity of the operation - the file operation which triggered
the operation may complete before the removal is finished (or even
started) and the removal may fail asynchronously. If a removal
operation is immmediately followed by another operation which expects
the specific name to be available (e.g. removal followed by rename
onto the same name), there's no way to make the latter operation
reliable.
The thing is there's no inherent reason for this to be asynchrnous.
All that's necessary to do this synchronous is a dedicated operation
which drops its own active ref and deactivates self. This patch
implements kernfs_remove_self() and its wrappers in sysfs and driver
core. kernfs_remove_self() is to be called from one of the file
operations, drops the active ref the task is holding, removes the self
node, and restores active ref to the dead node so that the ref is
balanced afterwards. __kernfs_remove() is updated so that it takes an
early exit if the target node is already fully removed so that the
active ref restored by kernfs_remove_self() after removal doesn't
confuse the deactivation path.
This makes implementing self-deleting nodes very easy. The normal
removal path doesn't even need to be changed to use
kernfs_remove_self() for the self-deleting node. The method can
invoke kernfs_remove_self() on itself before proceeding the normal
removal path. kernfs_remove() invoked on the node by the normal
deletion path will simply be ignored.
This will replace sysfs_schedule_callback(). A subtle feature of
sysfs_schedule_callback() is that it collapses multiple invocations -
even if multiple removals are triggered, the removal callback is run
only once. An equivalent effect can be achieved by testing the return
value of kernfs_remove_self() - only the one which gets %true return
value should proceed with actual deletion. All other instances of
kernfs_remove_self() will wait till the enclosing kernfs operation
which invoked the winning instance of kernfs_remove_self() finishes
and then return %false. This trivially makes all users of
kernfs_remove_self() automatically show correct synchronous behavior
even when there are multiple concurrent operations - all "echo 1 >
delete" instances will finish only after the whole operation is
completed by one of the instances.
Note that manipulation of active ref is implemented in separate public
functions - kernfs_[un]break_active_protection().
kernfs_remove_self() is the only user at the moment but this will be
used to cater to more complex cases.
v2: For !CONFIG_SYSFS, dummy version kernfs_remove_self() was missing
and sysfs_remove_file_self() had incorrect return type. Fix it.
Reported by kbuild test bot.
v3: kernfs_[un]break_active_protection() separated out from
kernfs_remove_self() and exposed as public API.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/core.c | 17 ++++++
fs/kernfs/dir.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++++-
fs/sysfs/file.c | 23 +++++++++
include/linux/device.h | 2 +
include/linux/kernfs.h | 8 +++
include/linux/sysfs.h | 7 +++
6 files changed, 194 insertions(+), 1 deletion(-)
(limited to 'fs')
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 2b567177ef78..9db57afcf81f 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -570,6 +570,23 @@ void device_remove_file(struct device *dev,
}
EXPORT_SYMBOL_GPL(device_remove_file);
+/**
+ * device_remove_file_self - remove sysfs attribute file from its own method.
+ * @dev: device.
+ * @attr: device attribute descriptor.
+ *
+ * See kernfs_remove_self() for details.
+ */
+bool device_remove_file_self(struct device *dev,
+ const struct device_attribute *attr)
+{
+ if (dev)
+ return sysfs_remove_file_self(&dev->kobj, &attr->attr);
+ else
+ return false;
+}
+EXPORT_SYMBOL_GPL(device_remove_file_self);
+
/**
* device_create_bin_file - create sysfs binary attribute file for device.
* @dev: device.
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index d0fd739bf82d..8c63ae1bccb6 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -761,7 +761,12 @@ static void __kernfs_remove(struct kernfs_node *kn)
lockdep_assert_held(&kernfs_mutex);
- if (!kn)
+ /*
+ * Short-circuit if non-root @kn has already finished removal.
+ * This is for kernfs_remove_self() which plays with active ref
+ * after removal.
+ */
+ if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb)))
return;
pr_debug("kernfs %s: removing\n", kn->name);
@@ -820,6 +825,137 @@ void kernfs_remove(struct kernfs_node *kn)
mutex_unlock(&kernfs_mutex);
}
+/**
+ * kernfs_break_active_protection - break out of active protection
+ * @kn: the self kernfs_node
+ *
+ * The caller must be running off of a kernfs operation which is invoked
+ * with an active reference - e.g. one of kernfs_ops. Each invocation of
+ * this function must also be matched with an invocation of
+ * kernfs_unbreak_active_protection().
+ *
+ * This function releases the active reference of @kn the caller is
+ * holding. Once this function is called, @kn may be removed at any point
+ * and the caller is solely responsible for ensuring that the objects it
+ * dereferences are accessible.
+ */
+void kernfs_break_active_protection(struct kernfs_node *kn)
+{
+ /*
+ * Take out ourself out of the active ref dependency chain. If
+ * we're called without an active ref, lockdep will complain.
+ */
+ kernfs_put_active(kn);
+}
+
+/**
+ * kernfs_unbreak_active_protection - undo kernfs_break_active_protection()
+ * @kn: the self kernfs_node
+ *
+ * If kernfs_break_active_protection() was called, this function must be
+ * invoked before finishing the kernfs operation. Note that while this
+ * function restores the active reference, it doesn't and can't actually
+ * restore the active protection - @kn may already or be in the process of
+ * being removed. Once kernfs_break_active_protection() is invoked, that
+ * protection is irreversibly gone for the kernfs operation instance.
+ *
+ * While this function may be called at any point after
+ * kernfs_break_active_protection() is invoked, its most useful location
+ * would be right before the enclosing kernfs operation returns.
+ */
+void kernfs_unbreak_active_protection(struct kernfs_node *kn)
+{
+ /*
+ * @kn->active could be in any state; however, the increment we do
+ * here will be undone as soon as the enclosing kernfs operation
+ * finishes and this temporary bump can't break anything. If @kn
+ * is alive, nothing changes. If @kn is being deactivated, the
+ * soon-to-follow put will either finish deactivation or restore
+ * deactivated state. If @kn is already removed, the temporary
+ * bump is guaranteed to be gone before @kn is released.
+ */
+ atomic_inc(&kn->active);
+ if (kernfs_lockdep(kn))
+ rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_);
+}
+
+/**
+ * kernfs_remove_self - remove a kernfs_node from its own method
+ * @kn: the self kernfs_node to remove
+ *
+ * The caller must be running off of a kernfs operation which is invoked
+ * with an active reference - e.g. one of kernfs_ops. This can be used to
+ * implement a file operation which deletes itself.
+ *
+ * For example, the "delete" file for a sysfs device directory can be
+ * implemented by invoking kernfs_remove_self() on the "delete" file
+ * itself. This function breaks the circular dependency of trying to
+ * deactivate self while holding an active ref itself. It isn't necessary
+ * to modify the usual removal path to use kernfs_remove_self(). The
+ * "delete" implementation can simply invoke kernfs_remove_self() on self
+ * before proceeding with the usual removal path. kernfs will ignore later
+ * kernfs_remove() on self.
+ *
+ * kernfs_remove_self() can be called multiple times concurrently on the
+ * same kernfs_node. Only the first one actually performs removal and
+ * returns %true. All others will wait until the kernfs operation which
+ * won self-removal finishes and return %false. Note that the losers wait
+ * for the completion of not only the winning kernfs_remove_self() but also
+ * the whole kernfs_ops which won the arbitration. This can be used to
+ * guarantee, for example, all concurrent writes to a "delete" file to
+ * finish only after the whole operation is complete.
+ */
+bool kernfs_remove_self(struct kernfs_node *kn)
+{
+ bool ret;
+
+ mutex_lock(&kernfs_mutex);
+ kernfs_break_active_protection(kn);
+
+ /*
+ * SUICIDAL is used to arbitrate among competing invocations. Only
+ * the first one will actually perform removal. When the removal
+ * is complete, SUICIDED is set and the active ref is restored
+ * while holding kernfs_mutex. The ones which lost arbitration
+ * waits for SUICDED && drained which can happen only after the
+ * enclosing kernfs operation which executed the winning instance
+ * of kernfs_remove_self() finished.
+ */
+ if (!(kn->flags & KERNFS_SUICIDAL)) {
+ kn->flags |= KERNFS_SUICIDAL;
+ __kernfs_remove(kn);
+ kn->flags |= KERNFS_SUICIDED;
+ ret = true;
+ } else {
+ wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
+ DEFINE_WAIT(wait);
+
+ while (true) {
+ prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
+
+ if ((kn->flags & KERNFS_SUICIDED) &&
+ atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
+ break;
+
+ mutex_unlock(&kernfs_mutex);
+ schedule();
+ mutex_lock(&kernfs_mutex);
+ }
+ finish_wait(waitq, &wait);
+ WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
+ ret = false;
+ }
+
+ /*
+ * This must be done while holding kernfs_mutex; otherwise, waiting
+ * for SUICIDED && deactivated could finish prematurely.
+ */
+ kernfs_unbreak_active_protection(kn);
+
+ mutex_unlock(&kernfs_mutex);
+ return ret;
+}
+
/**
* kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
* @parent: parent of the target
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 810cf6e613e5..1b8b91b67fdb 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -372,6 +372,29 @@ void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
+/**
+ * sysfs_remove_file_self - remove an object attribute from its own method
+ * @kobj: object we're acting for
+ * @attr: attribute descriptor
+ *
+ * See kernfs_remove_self() for details.
+ */
+bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
+{
+ struct kernfs_node *parent = kobj->sd;
+ struct kernfs_node *kn;
+ bool ret;
+
+ kn = kernfs_find_and_get(parent, attr->name);
+ if (WARN_ON_ONCE(!kn))
+ return false;
+
+ ret = kernfs_remove_self(kn);
+
+ kernfs_put(kn);
+ return ret;
+}
+
void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
{
int i;
diff --git a/include/linux/device.h b/include/linux/device.h
index 952b01033c32..1ff3f1697513 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -560,6 +560,8 @@ extern int device_create_file(struct device *device,
const struct device_attribute *entry);
extern void device_remove_file(struct device *dev,
const struct device_attribute *attr);
+extern bool device_remove_file_self(struct device *dev,
+ const struct device_attribute *attr);
extern int __must_check device_create_bin_file(struct device *dev,
const struct bin_attribute *attr);
extern void device_remove_bin_file(struct device *dev,
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 917bc6c1eb04..02ac33435808 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -43,6 +43,8 @@ enum kernfs_node_flag {
KERNFS_HAS_MMAP = 0x0080,
KERNFS_LOCKDEP = 0x0100,
KERNFS_STATIC_NAME = 0x0200,
+ KERNFS_SUICIDAL = 0x0400,
+ KERNFS_SUICIDED = 0x0800,
};
/* type-specific structures for kernfs_node union members */
@@ -234,6 +236,9 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target);
void kernfs_remove(struct kernfs_node *kn);
+void kernfs_break_active_protection(struct kernfs_node *kn);
+void kernfs_unbreak_active_protection(struct kernfs_node *kn);
+bool kernfs_remove_self(struct kernfs_node *kn);
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns);
int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
@@ -291,6 +296,9 @@ kernfs_create_link(struct kernfs_node *parent, const char *name,
static inline void kernfs_remove(struct kernfs_node *kn) { }
+static inline bool kernfs_remove_self(struct kernfs_node *kn)
+{ return false; }
+
static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
const char *name, const void *ns)
{ return -ENOSYS; }
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 30b2ebee6439..bd96c603ab6c 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -198,6 +198,7 @@ int __must_check sysfs_chmod_file(struct kobject *kobj,
const struct attribute *attr, umode_t mode);
void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
const void *ns);
+bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr);
void sysfs_remove_files(struct kobject *kobj, const struct attribute **attr);
int __must_check sysfs_create_bin_file(struct kobject *kobj,
@@ -301,6 +302,12 @@ static inline void sysfs_remove_file_ns(struct kobject *kobj,
{
}
+static inline bool sysfs_remove_file_self(struct kobject *kobj,
+ const struct attribute *attr)
+{
+ return false;
+}
+
static inline void sysfs_remove_files(struct kobject *kobj,
const struct attribute **attr)
{
--
cgit v1.2.3
From ce8b04aa6c9bdf211b921fdd18c040ea29516b97 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:03:05 -0500
Subject: sysfs, driver-core: remove unused
{sysfs|device}_schedule_callback_owner()
All device_schedule_callback_owner() users are converted to use
device_remove_file_self(). Remove now unused
{sysfs|device}_schedule_callback_owner().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/core.c | 33 ------------------
fs/sysfs/file.c | 92 --------------------------------------------------
include/linux/device.h | 11 +-----
include/linux/sysfs.h | 9 -----
4 files changed, 1 insertion(+), 144 deletions(-)
(limited to 'fs')
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 9db57afcf81f..4195364f9fdd 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -615,39 +615,6 @@ void device_remove_bin_file(struct device *dev,
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);
-/**
- * device_schedule_callback_owner - helper to schedule a callback for a device
- * @dev: device.
- * @func: callback function to invoke later.
- * @owner: module owning the callback routine
- *
- * Attribute methods must not unregister themselves or their parent device
- * (which would amount to the same thing). Attempts to do so will deadlock,
- * since unregistration is mutually exclusive with driver callbacks.
- *
- * Instead methods can call this routine, which will attempt to allocate
- * and schedule a workqueue request to call back @func with @dev as its
- * argument in the workqueue's process context. @dev will be pinned until
- * @func returns.
- *
- * This routine is usually called via the inline device_schedule_callback(),
- * which automatically sets @owner to THIS_MODULE.
- *
- * Returns 0 if the request was submitted, -ENOMEM if storage could not
- * be allocated, -ENODEV if a reference to @owner isn't available.
- *
- * NOTE: This routine won't work if CONFIG_SYSFS isn't set! It uses an
- * underlying sysfs routine (since it is intended for use by attribute
- * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
- */
-int device_schedule_callback_owner(struct device *dev,
- void (*func)(struct device *), struct module *owner)
-{
- return sysfs_schedule_callback(&dev->kobj,
- (void (*)(void *)) func, dev, owner);
-}
-EXPORT_SYMBOL_GPL(device_schedule_callback_owner);
-
static void klist_children_get(struct klist_node *n)
{
struct device_private *p = to_device_private_parent(n);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 1b8b91b67fdb..28cc1acd5439 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -453,95 +453,3 @@ void sysfs_remove_bin_file(struct kobject *kobj,
kernfs_remove_by_name(kobj->sd, attr->attr.name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
-
-struct sysfs_schedule_callback_struct {
- struct list_head workq_list;
- struct kobject *kobj;
- void (*func)(void *);
- void *data;
- struct module *owner;
- struct work_struct work;
-};
-
-static struct workqueue_struct *sysfs_workqueue;
-static DEFINE_MUTEX(sysfs_workq_mutex);
-static LIST_HEAD(sysfs_workq);
-static void sysfs_schedule_callback_work(struct work_struct *work)
-{
- struct sysfs_schedule_callback_struct *ss = container_of(work,
- struct sysfs_schedule_callback_struct, work);
-
- (ss->func)(ss->data);
- kobject_put(ss->kobj);
- module_put(ss->owner);
- mutex_lock(&sysfs_workq_mutex);
- list_del(&ss->workq_list);
- mutex_unlock(&sysfs_workq_mutex);
- kfree(ss);
-}
-
-/**
- * sysfs_schedule_callback - helper to schedule a callback for a kobject
- * @kobj: object we're acting for.
- * @func: callback function to invoke later.
- * @data: argument to pass to @func.
- * @owner: module owning the callback code
- *
- * sysfs attribute methods must not unregister themselves or their parent
- * kobject (which would amount to the same thing). Attempts to do so will
- * deadlock, since unregistration is mutually exclusive with driver
- * callbacks.
- *
- * Instead methods can call this routine, which will attempt to allocate
- * and schedule a workqueue request to call back @func with @data as its
- * argument in the workqueue's process context. @kobj will be pinned
- * until @func returns.
- *
- * Returns 0 if the request was submitted, -ENOMEM if storage could not
- * be allocated, -ENODEV if a reference to @owner isn't available,
- * -EAGAIN if a callback has already been scheduled for @kobj.
- */
-int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
- void *data, struct module *owner)
-{
- struct sysfs_schedule_callback_struct *ss, *tmp;
-
- if (!try_module_get(owner))
- return -ENODEV;
-
- mutex_lock(&sysfs_workq_mutex);
- list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
- if (ss->kobj == kobj) {
- module_put(owner);
- mutex_unlock(&sysfs_workq_mutex);
- return -EAGAIN;
- }
- mutex_unlock(&sysfs_workq_mutex);
-
- if (sysfs_workqueue == NULL) {
- sysfs_workqueue = create_singlethread_workqueue("sysfsd");
- if (sysfs_workqueue == NULL) {
- module_put(owner);
- return -ENOMEM;
- }
- }
-
- ss = kmalloc(sizeof(*ss), GFP_KERNEL);
- if (!ss) {
- module_put(owner);
- return -ENOMEM;
- }
- kobject_get(kobj);
- ss->kobj = kobj;
- ss->func = func;
- ss->data = data;
- ss->owner = owner;
- INIT_WORK(&ss->work, sysfs_schedule_callback_work);
- INIT_LIST_HEAD(&ss->workq_list);
- mutex_lock(&sysfs_workq_mutex);
- list_add_tail(&ss->workq_list, &sysfs_workq);
- mutex_unlock(&sysfs_workq_mutex);
- queue_work(sysfs_workqueue, &ss->work);
- return 0;
-}
-EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
diff --git a/include/linux/device.h b/include/linux/device.h
index 1ff3f1697513..fb1ba13f7665 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -566,12 +566,6 @@ extern int __must_check device_create_bin_file(struct device *dev,
const struct bin_attribute *attr);
extern void device_remove_bin_file(struct device *dev,
const struct bin_attribute *attr);
-extern int device_schedule_callback_owner(struct device *dev,
- void (*func)(struct device *dev), struct module *owner);
-
-/* This is a macro to avoid include problems with THIS_MODULE */
-#define device_schedule_callback(dev, func) \
- device_schedule_callback_owner(dev, func, THIS_MODULE)
/* device resource management */
typedef void (*dr_release_t)(struct device *dev, void *res);
@@ -931,10 +925,7 @@ extern int device_online(struct device *dev);
extern struct device *__root_device_register(const char *name,
struct module *owner);
-/*
- * This is a macro to avoid include problems with THIS_MODULE,
- * just as per what is done for device_schedule_callback() above.
- */
+/* This is a macro to avoid include problems with THIS_MODULE */
#define root_device_register(name) \
__root_device_register(name, THIS_MODULE)
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index bd96c603ab6c..14df05415af9 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -178,9 +178,6 @@ struct sysfs_ops {
#ifdef CONFIG_SYSFS
-int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
- void *data, struct module *owner);
-
int __must_check sysfs_create_dir_ns(struct kobject *kobj, const void *ns);
void sysfs_remove_dir(struct kobject *kobj);
int __must_check sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
@@ -249,12 +246,6 @@ int __must_check sysfs_init(void);
#else /* CONFIG_SYSFS */
-static inline int sysfs_schedule_callback(struct kobject *kobj,
- void (*func)(void *), void *data, struct module *owner)
-{
- return -ENOSYS;
-}
-
static inline int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
{
return 0;
--
cgit v1.2.3
From 07c7530dd46728e25e938d0eb291f8085435c365 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:08 -0500
Subject: kernfs: invoke dir_ops while holding active ref of the target node
kernfs_dir_ops are currently being invoked without any active
reference, which makes it tricky for the invoked operations to
determine whether the objects associated those nodes are safe to
access and will remain that way for the duration of such operations.
kernfs already has active_ref mechanism to deal with this which makes
the removal of a given node the synchronization point for gating the
file operations. There's no reason for dir_ops to be any different.
Update the dir_ops handling so that active_ref is held while the
dir_ops are executing. This guarantees that while a dir_ops is
executing the target nodes stay alive.
As kernfs_dir_ops doesn't have any in-kernel user at this point, this
doesn't affect anybody.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 33 ++++++++++++++++++++++++++++++---
include/linux/kernfs.h | 3 ++-
2 files changed, 32 insertions(+), 4 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8c63ae1bccb6..bfbfb48f4ad8 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -654,22 +654,36 @@ static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
{
struct kernfs_node *parent = dir->i_private;
struct kernfs_dir_ops *kdops = kernfs_root(parent)->dir_ops;
+ int ret;
if (!kdops || !kdops->mkdir)
return -EPERM;
- return kdops->mkdir(parent, dentry->d_name.name, mode);
+ if (!kernfs_get_active(parent))
+ return -ENODEV;
+
+ ret = kdops->mkdir(parent, dentry->d_name.name, mode);
+
+ kernfs_put_active(parent);
+ return ret;
}
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ int ret;
if (!kdops || !kdops->rmdir)
return -EPERM;
- return kdops->rmdir(kn);
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ ret = kdops->rmdir(kn);
+
+ kernfs_put_active(kn);
+ return ret;
}
static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
@@ -678,11 +692,24 @@ static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
struct kernfs_node *kn = old_dentry->d_fsdata;
struct kernfs_node *new_parent = new_dir->i_private;
struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ int ret;
if (!kdops || !kdops->rename)
return -EPERM;
- return kdops->rename(kn, new_parent, new_dentry->d_name.name);
+ if (!kernfs_get_active(kn))
+ return -ENODEV;
+
+ if (!kernfs_get_active(new_parent)) {
+ kernfs_put_active(kn);
+ return -ENODEV;
+ }
+
+ ret = kdops->rename(kn, new_parent, new_dentry->d_name.name);
+
+ kernfs_put_active(new_parent);
+ kernfs_put_active(kn);
+ return ret;
}
const struct inode_operations kernfs_dir_iops = {
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 02ac33435808..58a131ddc6a3 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -111,7 +111,8 @@ struct kernfs_node {
* kernfs_dir_ops may be specified on kernfs_create_root() to support
* directory manipulation syscalls. These optional callbacks are invoked
* on the matching syscalls and can perform any kernfs operations which
- * don't necessarily have to be the exact operation requested.
+ * don't necessarily have to be the exact operation requested. An active
+ * reference is held for each kernfs_node parameter.
*/
struct kernfs_dir_ops {
int (*mkdir)(struct kernfs_node *parent, const char *name,
--
cgit v1.2.3
From 90c07c895c87d38db100b6afcb686ab3ef0d6a64 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:09 -0500
Subject: kernfs: rename kernfs_dir_ops to kernfs_syscall_ops
We're gonna need non-dir syscall callbacks, which will make dir_ops a
misnomer. Let's rename kernfs_dir_ops to kernfs_syscall_ops.
This is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 25 +++++++++++++------------
include/linux/kernfs.h | 18 +++++++++---------
2 files changed, 22 insertions(+), 21 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index bfbfb48f4ad8..f58d2f16eaf7 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -527,13 +527,14 @@ EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
* kernfs_create_root - create a new kernfs hierarchy
- * @kdops: optional directory syscall operations for the hierarchy
+ * @scops: optional syscall operations for the hierarchy
* @priv: opaque data associated with the new directory
*
* Returns the root of the new hierarchy on success, ERR_PTR() value on
* failure.
*/
-struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
+struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
+ void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
@@ -556,7 +557,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
kn->priv = priv;
kn->dir.root = root;
- root->dir_ops = kdops;
+ root->syscall_ops = scops;
root->kn = kn;
init_waitqueue_head(&root->deactivate_waitq);
@@ -653,16 +654,16 @@ static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
umode_t mode)
{
struct kernfs_node *parent = dir->i_private;
- struct kernfs_dir_ops *kdops = kernfs_root(parent)->dir_ops;
+ struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops;
int ret;
- if (!kdops || !kdops->mkdir)
+ if (!scops || !scops->mkdir)
return -EPERM;
if (!kernfs_get_active(parent))
return -ENODEV;
- ret = kdops->mkdir(parent, dentry->d_name.name, mode);
+ ret = scops->mkdir(parent, dentry->d_name.name, mode);
kernfs_put_active(parent);
return ret;
@@ -671,16 +672,16 @@ static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
{
struct kernfs_node *kn = dentry->d_fsdata;
- struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
- if (!kdops || !kdops->rmdir)
+ if (!scops || !scops->rmdir)
return -EPERM;
if (!kernfs_get_active(kn))
return -ENODEV;
- ret = kdops->rmdir(kn);
+ ret = scops->rmdir(kn);
kernfs_put_active(kn);
return ret;
@@ -691,10 +692,10 @@ static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
{
struct kernfs_node *kn = old_dentry->d_fsdata;
struct kernfs_node *new_parent = new_dir->i_private;
- struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+ struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
int ret;
- if (!kdops || !kdops->rename)
+ if (!scops || !scops->rename)
return -EPERM;
if (!kernfs_get_active(kn))
@@ -705,7 +706,7 @@ static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry,
return -ENODEV;
}
- ret = kdops->rename(kn, new_parent, new_dentry->d_name.name);
+ ret = scops->rename(kn, new_parent, new_dentry->d_name.name);
kernfs_put_active(new_parent);
kernfs_put_active(kn);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 58a131ddc6a3..5ddc47450335 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -108,13 +108,13 @@ struct kernfs_node {
};
/*
- * kernfs_dir_ops may be specified on kernfs_create_root() to support
- * directory manipulation syscalls. These optional callbacks are invoked
- * on the matching syscalls and can perform any kernfs operations which
- * don't necessarily have to be the exact operation requested. An active
- * reference is held for each kernfs_node parameter.
+ * kernfs_syscall_ops may be specified on kernfs_create_root() to support
+ * syscalls. These optional callbacks are invoked on the matching syscalls
+ * and can perform any kernfs operations which don't necessarily have to be
+ * the exact operation requested. An active reference is held for each
+ * kernfs_node parameter.
*/
-struct kernfs_dir_ops {
+struct kernfs_syscall_ops {
int (*mkdir)(struct kernfs_node *parent, const char *name,
umode_t mode);
int (*rmdir)(struct kernfs_node *kn);
@@ -128,7 +128,7 @@ struct kernfs_root {
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
- struct kernfs_dir_ops *dir_ops;
+ struct kernfs_syscall_ops *syscall_ops;
wait_queue_head_t deactivate_waitq;
};
@@ -219,7 +219,7 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
-struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops,
+struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
@@ -273,7 +273,7 @@ static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
static inline struct kernfs_root *
-kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
+kernfs_create_root(struct kernfs_syscall_ops *scops, void *priv)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
--
cgit v1.2.3
From 6a7fed4eefddad48224f1c9d534b4e262f0897f6 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:10 -0500
Subject: kernfs: implement kernfs_syscall_ops->remount_fs() and
->show_options()
Add two super_block related syscall callbacks ->remount_fs() and
->show_options() to kernfs_syscall_ops. These simply forward the
matching super_operations.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/mount.c | 23 +++++++++++++++++++++++
include/linux/kernfs.h | 3 +++
2 files changed, 26 insertions(+)
(limited to 'fs')
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 0d6ce895a9ee..70cc6983d9b5 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -19,10 +19,33 @@
struct kmem_cache *kernfs_node_cache;
+static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+ struct kernfs_root *root = kernfs_info(sb)->root;
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->remount_fs)
+ return scops->remount_fs(root, flags, data);
+ return 0;
+}
+
+static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
+{
+ struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
+ struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+ if (scops && scops->show_options)
+ return scops->show_options(sf, root);
+ return 0;
+}
+
static const struct super_operations kernfs_sops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.evict_inode = kernfs_evict_inode,
+
+ .remount_fs = kernfs_sop_remount_fs,
+ .show_options = kernfs_sop_show_options,
};
static int kernfs_fill_super(struct super_block *sb)
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5ddc47450335..5d5b7e947294 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -115,6 +115,9 @@ struct kernfs_node {
* kernfs_node parameter.
*/
struct kernfs_syscall_ops {
+ int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
+ int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
+
int (*mkdir)(struct kernfs_node *parent, const char *name,
umode_t mode);
int (*rmdir)(struct kernfs_node *kn);
--
cgit v1.2.3
From b9c9dad0c457d32cf8c7d2e413463c8414c7a7a7 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:11 -0500
Subject: kernfs: add missing kernfs_active() checks in directory operations
kernfs_iop_lookup(), kernfs_dir_pos() and kernfs_dir_next_pos() were
missing kernfs_active() tests before using the found kernfs_node. As
deactivated state is currently visible only while a node is being
removed, this doesn't pose an actual problem. e.g. lookup succeeding
on a deactivated node doesn't harm anything as the eventual file
operations are gonna fail and those failures are indistinguishible
from the cases in which the lookups had happened before the node was
deactivated.
However, we're gonna allow new nodes to be created deactivated and
then activated explicitly by the kernfs user when it sees fit. This
is to support atomically making multiple nodes visible to userland and
thus those nodes must not be visible to userland before activated.
Let's plug the lookup and readdir holes so that deactivated nodes are
invisible to userland.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f58d2f16eaf7..89f8462f337e 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -629,7 +629,7 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
/* no such entry */
- if (!kn) {
+ if (!kn || !kernfs_active(kn)) {
ret = NULL;
goto out_unlock;
}
@@ -1112,8 +1112,8 @@ static struct kernfs_node *kernfs_dir_pos(const void *ns,
break;
}
}
- /* Skip over entries in the wrong namespace */
- while (pos && pos->ns != ns) {
+ /* Skip over entries which are dying/dead or in the wrong namespace */
+ while (pos && (!kernfs_active(pos) || pos->ns != ns)) {
struct rb_node *node = rb_next(&pos->rb);
if (!node)
pos = NULL;
@@ -1127,14 +1127,15 @@ static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
{
pos = kernfs_dir_pos(ns, parent, ino, pos);
- if (pos)
+ if (pos) {
do {
struct rb_node *node = rb_next(&pos->rb);
if (!node)
pos = NULL;
else
pos = rb_to_kn(node);
- } while (pos && pos->ns != ns);
+ } while (pos && (!kernfs_active(pos) || pos->ns != ns));
+ }
return pos;
}
--
cgit v1.2.3
From d35258ef702cca0c4e66d799f8e38b78c02ce8a5 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:12 -0500
Subject: kernfs: allow nodes to be created in the deactivated state
Currently, kernfs_nodes are made visible to userland on creation,
which makes it difficult for kernfs users to atomically succeed or
fail creation of multiple nodes. In addition, if something fails
after creating some nodes, the created nodes might already be in use
and their active refs need to be drained for removal, which has the
potential to introduce tricky reverse locking dependency on active_ref
depending on how the error path is synchronized.
This patch introduces per-root flag KERNFS_ROOT_CREATE_DEACTIVATED.
If set, all nodes under the root are created in the deactivated state
and stay invisible to userland until explicitly enabled by the new
kernfs_activate() API. Also, nodes which have never been activated
are guaranteed to bypass draining on removal thus allowing error paths
to not worry about lockding dependency on active_ref draining.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 71 +++++++++++++++++++++++++++++++++++++++++++++-----
fs/sysfs/mount.c | 2 +-
include/linux/kernfs.h | 15 +++++++++--
3 files changed, 78 insertions(+), 10 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 89f8462f337e..3cff0a233cd1 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -435,7 +435,7 @@ int kernfs_add_one(struct kernfs_node *kn)
goto out_unlock;
ret = -ENOENT;
- if (!kernfs_active(parent))
+ if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
goto out_unlock;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
@@ -451,9 +451,19 @@ int kernfs_add_one(struct kernfs_node *kn)
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
- /* Mark the entry added into directory tree */
- atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
- ret = 0;
+ mutex_unlock(&kernfs_mutex);
+
+ /*
+ * Activate the new node unless CREATE_DEACTIVATED is requested.
+ * If not activated here, the kernfs user is responsible for
+ * activating the node with kernfs_activate(). A node which hasn't
+ * been activated is not visible to userland and its removal won't
+ * trigger deactivation.
+ */
+ if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+ return 0;
+
out_unlock:
mutex_unlock(&kernfs_mutex);
return ret;
@@ -528,13 +538,14 @@ EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy
+ * @flags: KERNFS_ROOT_* flags
* @priv: opaque data associated with the new directory
*
* Returns the root of the new hierarchy on success, ERR_PTR() value on
* failure.
*/
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
- void *priv)
+ unsigned int flags, void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
@@ -553,14 +564,17 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
return ERR_PTR(-ENOMEM);
}
- atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
kn->priv = priv;
kn->dir.root = root;
root->syscall_ops = scops;
+ root->flags = flags;
root->kn = kn;
init_waitqueue_head(&root->deactivate_waitq);
+ if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+
return root;
}
@@ -783,6 +797,40 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
return pos->parent;
}
+/**
+ * kernfs_activate - activate a node which started deactivated
+ * @kn: kernfs_node whose subtree is to be activated
+ *
+ * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
+ * needs to be explicitly activated. A node which hasn't been activated
+ * isn't visible to userland and deactivation is skipped during its
+ * removal. This is useful to construct atomic init sequences where
+ * creation of multiple nodes should either succeed or fail atomically.
+ *
+ * The caller is responsible for ensuring that this function is not called
+ * after kernfs_remove*() is invoked on @kn.
+ */
+void kernfs_activate(struct kernfs_node *kn)
+{
+ struct kernfs_node *pos;
+
+ mutex_lock(&kernfs_mutex);
+
+ pos = NULL;
+ while ((pos = kernfs_next_descendant_post(pos, kn))) {
+ if (!pos || (pos->flags & KERNFS_ACTIVATED))
+ continue;
+
+ WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
+ WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
+
+ atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
+ pos->flags |= KERNFS_ACTIVATED;
+ }
+
+ mutex_unlock(&kernfs_mutex);
+}
+
static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;
@@ -817,7 +865,16 @@ static void __kernfs_remove(struct kernfs_node *kn)
*/
kernfs_get(pos);
- kernfs_drain(pos);
+ /*
+ * Drain iff @kn was activated. This avoids draining and
+ * its lockdep annotations for nodes which have never been
+ * activated and allows embedding kernfs_remove() in create
+ * error paths without worrying about draining.
+ */
+ if (kn->flags & KERNFS_ACTIVATED)
+ kernfs_drain(pos);
+ else
+ WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 6211230814fd..5c7fdd9c6811 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -62,7 +62,7 @@ int __init sysfs_init(void)
{
int err;
- sysfs_root = kernfs_create_root(NULL, NULL);
+ sysfs_root = kernfs_create_root(NULL, 0, NULL);
if (IS_ERR(sysfs_root))
return PTR_ERR(sysfs_root);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5d5b7e947294..4520c86f5cb4 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -38,6 +38,7 @@ enum kernfs_node_type {
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {
+ KERNFS_ACTIVATED = 0x0010,
KERNFS_NS = 0x0020,
KERNFS_HAS_SEQ_SHOW = 0x0040,
KERNFS_HAS_MMAP = 0x0080,
@@ -47,6 +48,11 @@ enum kernfs_node_flag {
KERNFS_SUICIDED = 0x0800,
};
+/* @flags for kernfs_create_root() */
+enum kernfs_root_flag {
+ KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
+};
+
/* type-specific structures for kernfs_node union members */
struct kernfs_elem_dir {
unsigned long subdirs;
@@ -128,6 +134,7 @@ struct kernfs_syscall_ops {
struct kernfs_root {
/* published fields */
struct kernfs_node *kn;
+ unsigned int flags; /* KERNFS_ROOT_* flags */
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
@@ -223,7 +230,7 @@ void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
- void *priv);
+ unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
@@ -239,6 +246,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target);
+void kernfs_activate(struct kernfs_node *kn);
void kernfs_remove(struct kernfs_node *kn);
void kernfs_break_active_protection(struct kernfs_node *kn);
void kernfs_unbreak_active_protection(struct kernfs_node *kn);
@@ -276,7 +284,8 @@ static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
static inline struct kernfs_root *
-kernfs_create_root(struct kernfs_syscall_ops *scops, void *priv)
+kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
+ void *priv)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
@@ -298,6 +307,8 @@ kernfs_create_link(struct kernfs_node *parent, const char *name,
struct kernfs_node *target)
{ return ERR_PTR(-ENOSYS); }
+static inline void kernfs_activate(struct kernfs_node *kn) { }
+
static inline void kernfs_remove(struct kernfs_node *kn) { }
static inline bool kernfs_remove_self(struct kernfs_node *kn)
--
cgit v1.2.3
From 4d3773c4bb41ed5228f1ab7a4a52b79e17b10515 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:13 -0500
Subject: kernfs: implement kernfs_ops->atomic_write_len
A write to a kernfs_node is buffered through a kernel buffer. Writes
<= PAGE_SIZE are performed atomically, while larger ones are executed
in PAGE_SIZE chunks. While this is enough for sysfs, cgroup which is
scheduled to be converted to use kernfs needs a bit more control over
it.
This patch adds kernfs_ops->atomic_write_len. If not set (zero), the
behavior stays the same. If set, writes upto the size are executed
atomically and larger writes are rejected with -E2BIG.
A different implementation strategy would be allowing configuring
chunking size while making the original write size available to the
write method; however, such strategy, while being more complicated,
doesn't really buy anything. If the write implementation has to
handle chunking, the specific chunk size shouldn't matter all that
much.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/file.c | 49 +++++++++++++++++++++++++++++++------------------
include/linux/kernfs.h | 8 ++++++--
2 files changed, 37 insertions(+), 20 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 10a8c91c49d6..ddcb471b9cc9 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -252,19 +252,9 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
struct kernfs_open_file *of = kernfs_of(file);
- ssize_t len = min_t(size_t, count, PAGE_SIZE);
const struct kernfs_ops *ops;
- char *buf;
-
- buf = kmalloc(len + 1, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- if (copy_from_user(buf, user_buf, len)) {
- len = -EFAULT;
- goto out_free;
- }
- buf[len] = '\0'; /* guarantee string termination */
+ char *buf = NULL;
+ ssize_t len;
/*
* @of->mutex nests outside active ref and is just to ensure that
@@ -273,22 +263,45 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
mutex_unlock(&of->mutex);
- len = -ENODEV;
- goto out_free;
+ return -ENODEV;
}
ops = kernfs_ops(of->kn);
- if (ops->write)
- len = ops->write(of, buf, len, *ppos);
- else
+ if (!ops->write) {
len = -EINVAL;
+ goto out_unlock;
+ }
+
+ if (ops->atomic_write_len) {
+ len = count;
+ if (len > ops->atomic_write_len) {
+ len = -E2BIG;
+ goto out_unlock;
+ }
+ } else {
+ len = min_t(size_t, count, PAGE_SIZE);
+ }
+
+ buf = kmalloc(len + 1, GFP_KERNEL);
+ if (!buf) {
+ len = -ENOMEM;
+ goto out_unlock;
+ }
+ if (copy_from_user(buf, user_buf, len)) {
+ len = -EFAULT;
+ goto out_unlock;
+ }
+ buf[len] = '\0'; /* guarantee string termination */
+
+ len = ops->write(of, buf, len, *ppos);
+out_unlock:
kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
if (len > 0)
*ppos += len;
-out_free:
+
kfree(buf);
return len;
}
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 4520c86f5cb4..47f5235a097a 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -178,9 +178,13 @@ struct kernfs_ops {
loff_t off);
/*
- * write() is bounced through kernel buffer and a write larger than
- * PAGE_SIZE results in partial operation of PAGE_SIZE.
+ * write() is bounced through kernel buffer. If atomic_write_len
+ * is not set, a write larger than PAGE_SIZE results in partial
+ * operations of PAGE_SIZE chunks. If atomic_write_len is set,
+ * writes upto the specified size are executed atomically but
+ * larger ones are rejected with -E2BIG.
*/
+ size_t atomic_write_len;
ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
loff_t off);
--
cgit v1.2.3
From 0c23b2259a4850494e2c53e864ea840597c6cdd3 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:15 -0500
Subject: kernfs: implement kernfs_node_from_dentry(), kernfs_root_from_sb()
and kernfs_rename()
Implement helpers to determine node from dentry and root from
super_block. Also add a kernfs_rename_ns() wrapper which assumes NULL
namespace. These generally make sense and will be used by cgroup.
v2: Some dummy implementations for !CONFIG_SYSFS was missing. Fixed.
Reported by kbuild test robot.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 18 ++++++++++++++++++
fs/kernfs/mount.c | 14 ++++++++++++++
include/linux/kernfs.h | 16 ++++++++++++++++
3 files changed, 48 insertions(+)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 3cff0a233cd1..42a250f83b98 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -350,6 +350,24 @@ const struct dentry_operations kernfs_dops = {
.d_release = kernfs_dop_release,
};
+/**
+ * kernfs_node_from_dentry - determine kernfs_node associated with a dentry
+ * @dentry: the dentry in question
+ *
+ * Return the kernfs_node associated with @dentry. If @dentry is not a
+ * kernfs one, %NULL is returned.
+ *
+ * While the returned kernfs_node will stay accessible as long as @dentry
+ * is accessible, the returned node can be in any state and the caller is
+ * fully responsible for determining what's accessible.
+ */
+struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
+{
+ if (dentry->d_op == &kernfs_dops)
+ return dentry->d_fsdata;
+ return NULL;
+}
+
static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
const char *name, umode_t mode,
unsigned flags)
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 70cc6983d9b5..e5b28b0ebc37 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -48,6 +48,20 @@ static const struct super_operations kernfs_sops = {
.show_options = kernfs_sop_show_options,
};
+/**
+ * kernfs_root_from_sb - determine kernfs_root associated with a super_block
+ * @sb: the super_block in question
+ *
+ * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
+ * %NULL is returned.
+ */
+struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
+{
+ if (sb->s_op == &kernfs_sops)
+ return kernfs_info(sb)->root;
+ return NULL;
+}
+
static int kernfs_fill_super(struct super_block *sb)
{
struct kernfs_super_info *info = kernfs_info(sb);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 9ca0f09757a1..9c899040c05e 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -234,6 +234,9 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
+struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
+struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
+
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
@@ -288,6 +291,12 @@ kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
+static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
+{ return NULL; }
+
+static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
+{ return NULL; }
+
static inline struct kernfs_root *
kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
void *priv)
@@ -388,6 +397,13 @@ static inline int kernfs_remove_by_name(struct kernfs_node *parent,
return kernfs_remove_by_name_ns(parent, name, NULL);
}
+static inline int kernfs_rename(struct kernfs_node *kn,
+ struct kernfs_node *new_parent,
+ const char *new_name)
+{
+ return kernfs_rename_ns(kn, new_parent, new_name, NULL);
+}
+
static inline struct dentry *
kernfs_mount(struct file_system_type *fs_type, int flags,
struct kernfs_root *root)
--
cgit v1.2.3
From 3eef34ad7dc369b7183ec383908aff3da2f6e5ec Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 7 Feb 2014 13:32:07 -0500
Subject: kernfs: implement kernfs_get_parent(), kernfs_name/path() and friends
kernfs_node->parent and ->name are currently marked as "published"
indicating that kernfs users may access them directly; however, those
fields may get updated by kernfs_rename[_ns]() and unrestricted access
may lead to erroneous values or oops.
Protect ->parent and ->name updates with a irq-safe spinlock
kernfs_rename_lock and implement the following accessors for these
fields.
* kernfs_name() - format the node's name into the specified buffer
* kernfs_path() - format the node's path into the specified buffer
* pr_cont_kernfs_name() - pr_cont a node's name (doesn't need buffer)
* pr_cont_kernfs_path() - pr_cont a node's path (doesn't need buffer)
* kernfs_get_parent() - pin and return a node's parent
All can be called under any context. The recursive sysfs_pathname()
in fs/sysfs/dir.c is replaced with kernfs_path() and
sysfs_rename_dir_ns() is updated to use kernfs_get_parent() instead of
dereferencing parent directly.
v2: Dummy definition of kernfs_path() for !CONFIG_KERNFS was missing
static inline making it cause a lot of build warnings. Add it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 175 ++++++++++++++++++++++++++++++++++++++++++++++---
fs/sysfs/dir.c | 44 ++++---------
include/linux/kernfs.h | 26 +++++++-
3 files changed, 203 insertions(+), 42 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 42a250f83b98..a347792c2e5a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -19,6 +19,8 @@
#include "kernfs-internal.h"
DEFINE_MUTEX(kernfs_mutex);
+static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
+static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
@@ -37,6 +39,141 @@ static bool kernfs_lockdep(struct kernfs_node *kn)
#endif
}
+static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
+}
+
+static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf,
+ size_t buflen)
+{
+ char *p = buf + buflen;
+ int len;
+
+ *--p = '\0';
+
+ do {
+ len = strlen(kn->name);
+ if (p - buf < len + 1) {
+ buf[0] = '\0';
+ p = NULL;
+ break;
+ }
+ p -= len;
+ memcpy(p, kn->name, len);
+ *--p = '/';
+ kn = kn->parent;
+ } while (kn && kn->parent);
+
+ return p;
+}
+
+/**
+ * kernfs_name - obtain the name of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Copies the name of @kn into @buf of @buflen bytes. The behavior is
+ * similar to strlcpy(). It returns the length of @kn's name and if @buf
+ * isn't long enough, it's filled upto @buflen-1 and nul terminated.
+ *
+ * This function can be called from any context.
+ */
+int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ unsigned long flags;
+ int ret;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ ret = kernfs_name_locked(kn, buf, buflen);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+ return ret;
+}
+
+/**
+ * kernfs_path - build full path of a given node
+ * @kn: kernfs_node of interest
+ * @buf: buffer to copy @kn's name into
+ * @buflen: size of @buf
+ *
+ * Builds and returns the full path of @kn in @buf of @buflen bytes. The
+ * path is built from the end of @buf so the returned pointer usually
+ * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated
+ * and %NULL is returned.
+ */
+char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen)
+{
+ unsigned long flags;
+ char *p;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ p = kernfs_path_locked(kn, buf, buflen);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+ return p;
+}
+
+/**
+ * pr_cont_kernfs_name - pr_cont name of a kernfs_node
+ * @kn: kernfs_node of interest
+ *
+ * This function can be called from any context.
+ */
+void pr_cont_kernfs_name(struct kernfs_node *kn)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ kernfs_name_locked(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
+ pr_cont("%s", kernfs_pr_cont_buf);
+
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+}
+
+/**
+ * pr_cont_kernfs_path - pr_cont path of a kernfs_node
+ * @kn: kernfs_node of interest
+ *
+ * This function can be called from any context.
+ */
+void pr_cont_kernfs_path(struct kernfs_node *kn)
+{
+ unsigned long flags;
+ char *p;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+ p = kernfs_path_locked(kn, kernfs_pr_cont_buf,
+ sizeof(kernfs_pr_cont_buf));
+ if (p)
+ pr_cont("%s", p);
+ else
+ pr_cont("<name too long>");
+
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+}
+
+/**
+ * kernfs_get_parent - determine the parent node and pin it
+ * @kn: kernfs_node of interest
+ *
+ * Determines @kn's parent, pins and returns it. This function can be
+ * called from any context.
+ */
+struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
+{
+ struct kernfs_node *parent;
+ unsigned long flags;
+
+ spin_lock_irqsave(&kernfs_rename_lock, flags);
+ parent = kn->parent;
+ kernfs_get(parent);
+ spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+
+ return parent;
+}
+
/**
* kernfs_name_hash
* @name: Null terminated string to hash
@@ -1103,8 +1240,14 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name, const void *new_ns)
{
+ struct kernfs_node *old_parent;
+ const char *old_name = NULL;
int error;
+ /* can't move or rename root */
+ if (!kn->parent)
+ return -EINVAL;
+
mutex_lock(&kernfs_mutex);
error = -ENOENT;
@@ -1126,13 +1269,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
new_name = kstrdup(new_name, GFP_KERNEL);
if (!new_name)
goto out;
-
- if (kn->flags & KERNFS_STATIC_NAME)
- kn->flags &= ~KERNFS_STATIC_NAME;
- else
- kfree(kn->name);
-
- kn->name = new_name;
+ } else {
+ new_name = NULL;
}
/*
@@ -1140,12 +1278,29 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
*/
kernfs_unlink_sibling(kn);
kernfs_get(new_parent);
- kernfs_put(kn->parent);
- kn->ns = new_ns;
- kn->hash = kernfs_name_hash(kn->name, kn->ns);
+
+ /* rename_lock protects ->parent and ->name accessors */
+ spin_lock_irq(&kernfs_rename_lock);
+
+ old_parent = kn->parent;
kn->parent = new_parent;
+
+ kn->ns = new_ns;
+ if (new_name) {
+ if (!(kn->flags & KERNFS_STATIC_NAME))
+ old_name = kn->name;
+ kn->flags &= ~KERNFS_STATIC_NAME;
+ kn->name = new_name;
+ }
+
+ spin_unlock_irq(&kernfs_rename_lock);
+
+ kn->hash = kernfs_name_hash(new_name, new_ns);
kernfs_link_sibling(kn);
+ kernfs_put(old_parent);
+ kfree(old_name);
+
error = 0;
out:
mutex_unlock(&kernfs_mutex);
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index ee0d761c3179..0b45ff42f374 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -19,39 +19,18 @@
DEFINE_SPINLOCK(sysfs_symlink_target_lock);
-/**
- * sysfs_pathname - return full path to sysfs dirent
- * @kn: kernfs_node whose path we want
- * @path: caller allocated buffer of size PATH_MAX
- *
- * Gives the name "/" to the sysfs_root entry; any path returned
- * is relative to wherever sysfs is mounted.
- */
-static char *sysfs_pathname(struct kernfs_node *kn, char *path)
-{
- if (kn->parent) {
- sysfs_pathname(kn->parent, path);
- strlcat(path, "/", PATH_MAX);
- }
- strlcat(path, kn->name, PATH_MAX);
- return path;
-}
-
void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
{
- char *path;
+ char *buf, *path = NULL;
- path = kzalloc(PATH_MAX, GFP_KERNEL);
- if (path) {
- sysfs_pathname(parent, path);
- strlcat(path, "/", PATH_MAX);
- strlcat(path, name, PATH_MAX);
- }
+ buf = kzalloc(PATH_MAX, GFP_KERNEL);
+ if (buf)
+ path = kernfs_path(parent, buf, PATH_MAX);
- WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s'\n",
- path ? path : name);
+ WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n",
+ path, name);
- kfree(path);
+ kfree(buf);
}
/**
@@ -122,9 +101,13 @@ void sysfs_remove_dir(struct kobject *kobj)
int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
const void *new_ns)
{
- struct kernfs_node *parent = kobj->sd->parent;
+ struct kernfs_node *parent;
+ int ret;
- return kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
+ parent = kernfs_get_parent(kobj->sd);
+ ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
+ kernfs_put(parent);
+ return ret;
}
int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
@@ -133,7 +116,6 @@ int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
struct kernfs_node *kn = kobj->sd;
struct kernfs_node *new_parent;
- BUG_ON(!kn->parent);
new_parent = new_parent_kobj && new_parent_kobj->sd ?
new_parent_kobj->sd : sysfs_root_kn;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 9c899040c05e..8736ee86a1d6 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -91,7 +91,12 @@ struct kernfs_node {
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
- /* the following two fields are published */
+ /*
+ * Use kernfs_get_parent() and kernfs_name/path() instead of
+ * accessing the following two fields directly. If the node is
+ * never moved to a different parent, it is safe to access the
+ * parent directly.
+ */
struct kernfs_node *parent;
const char *name;
@@ -229,6 +234,12 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
return kn->flags & KERNFS_NS;
}
+int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
+char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
+ size_t buflen);
+void pr_cont_kernfs_name(struct kernfs_node *kn);
+void pr_cont_kernfs_path(struct kernfs_node *kn);
+struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns);
void kernfs_get(struct kernfs_node *kn);
@@ -283,6 +294,19 @@ static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
{ return false; }
+static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
+{ return -ENOSYS; }
+
+static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
+ size_t buflen)
+{ return NULL; }
+
+static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
+static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
+
+static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
+{ return NULL; }
+
static inline struct kernfs_node *
kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
const void *ns)
--
cgit v1.2.3
From ba341d55a420ab4fdd1a53fd395fd59bd65de880 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 3 Feb 2014 14:09:17 -0500
Subject: kernfs: add CONFIG_KERNFS
As sysfs was kernfs's only user, kernfs has been piggybacking on
CONFIG_SYSFS; however, kernfs is scheduled to grow a new user very
soon. Introduce a separate config option CONFIG_KERNFS which is to be
selected by kernfs users.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/Kconfig | 1 +
fs/Makefile | 3 ++-
fs/kernfs/Kconfig | 7 +++++++
fs/sysfs/Kconfig | 1 +
include/linux/kernfs.h | 6 +++---
5 files changed, 14 insertions(+), 4 deletions(-)
create mode 100644 fs/kernfs/Kconfig
(limited to 'fs')
diff --git a/fs/Kconfig b/fs/Kconfig
index 7385e54be4b9..312393f32948 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -96,6 +96,7 @@ endif # BLOCK
menu "Pseudo filesystems"
source "fs/proc/Kconfig"
+source "fs/kernfs/Kconfig"
source "fs/sysfs/Kconfig"
config TMPFS
diff --git a/fs/Makefile b/fs/Makefile
index 47ac07bb4acc..f9cb9876e466 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -52,7 +52,8 @@ obj-$(CONFIG_FHANDLE) += fhandle.o
obj-y += quota/
obj-$(CONFIG_PROC_FS) += proc/
-obj-$(CONFIG_SYSFS) += sysfs/ kernfs/
+obj-$(CONFIG_KERNFS) += kernfs/
+obj-$(CONFIG_SYSFS) += sysfs/
obj-$(CONFIG_CONFIGFS_FS) += configfs/
obj-y += devpts/
diff --git a/fs/kernfs/Kconfig b/fs/kernfs/Kconfig
new file mode 100644
index 000000000000..397b5f7a7a16
--- /dev/null
+++ b/fs/kernfs/Kconfig
@@ -0,0 +1,7 @@
+#
+# KERNFS should be selected by its users
+#
+
+config KERNFS
+ bool
+ default n
diff --git a/fs/sysfs/Kconfig b/fs/sysfs/Kconfig
index 8c41feacbac5..b2756014508c 100644
--- a/fs/sysfs/Kconfig
+++ b/fs/sysfs/Kconfig
@@ -1,6 +1,7 @@
config SYSFS
bool "sysfs file system support" if EXPERT
default y
+ select KERNFS
help
The sysfs filesystem is a virtual filesystem that the kernel uses to
export internal kernel objects, their attributes, and their
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 8736ee86a1d6..649497a56a95 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -201,7 +201,7 @@ struct kernfs_ops {
#endif
};
-#ifdef CONFIG_SYSFS
+#ifdef CONFIG_KERNFS
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{
@@ -284,7 +284,7 @@ void kernfs_kill_sb(struct super_block *sb);
void kernfs_init(void);
-#else /* CONFIG_SYSFS */
+#else /* CONFIG_KERNFS */
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{ return 0; } /* whatever */
@@ -379,7 +379,7 @@ static inline void kernfs_kill_sb(struct super_block *sb) { }
static inline void kernfs_init(void) { }
-#endif /* CONFIG_SYSFS */
+#endif /* CONFIG_KERNFS */
static inline struct kernfs_node *
kernfs_find_and_get(struct kernfs_node *kn, const char *name)
--
cgit v1.2.3
From 9561a8961c708ff6ba3e71a817af0f16bdc1d885 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 10 Feb 2014 17:57:09 -0500
Subject: kernfs: fix hash calculation in kernfs_rename_ns()
3eef34ad7dc3 ("kernfs: implement kernfs_get_parent(),
kernfs_name/path() and friends") restructured kernfs_rename_ns() such
that new name assignment happens under kernfs_rename_lock;
unfortunately, it mistakenly passed NULL to kernfs_name_hash() to
calculate the new hash if the name hasn't changed, which can lead to
oops.
Fix it by using kn->name and kn->ns when calculating the new hash.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dan Carpenter dan.carpenter@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a347792c2e5a..a0f99b7f84b2 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -1295,7 +1295,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
spin_unlock_irq(&kernfs_rename_lock);
- kn->hash = kernfs_name_hash(new_name, new_ns);
+ kn->hash = kernfs_name_hash(kn->name, kn->ns);
kernfs_link_sibling(kn);
kernfs_put(old_parent);
--
cgit v1.2.3
From f41c593454943b80a2017c8a2a3d6b1d0b0a6f89 Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@huawei.com>
Date: Fri, 14 Feb 2014 16:57:27 +0800
Subject: kernfs: fix kernfs_node_from_dentry()
Currently kernfs_node_from_dentry() returns NULL for root dentry,
because root_dentry->d_op == NULL.
Due to this bug cgroupstats_build() returns -EINVAL for root cgroup.
# mount -t cgroup -o cpuacct /cgroup
# Documentation/accounting/getdelays -C /cgroup
fatal reply error, errno -22
With this fix:
# Documentation/accounting/getdelays -C /cgroup
sleeping 305, blocked 0, running 1, stopped 0, uninterruptible 1
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 2 +-
fs/kernfs/kernfs-internal.h | 1 +
fs/kernfs/mount.c | 2 +-
3 files changed, 3 insertions(+), 2 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a0f99b7f84b2..8245d3b34894 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -500,7 +500,7 @@ const struct dentry_operations kernfs_dops = {
*/
struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
{
- if (dentry->d_op == &kernfs_dops)
+ if (dentry->d_sb->s_op == &kernfs_sops)
return dentry->d_fsdata;
return NULL;
}
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index a91d7a1113d9..8be13b2a079b 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -65,6 +65,7 @@ struct kernfs_super_info {
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
+extern const struct super_operations kernfs_sops;
extern struct kmem_cache *kernfs_node_cache;
/*
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index e5b28b0ebc37..405279b5517b 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -39,7 +39,7 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
return 0;
}
-static const struct super_operations kernfs_sops = {
+const struct super_operations kernfs_sops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.evict_inode = kernfs_evict_inode,
--
cgit v1.2.3
From aabaf4c2050d21d39fe11eec889c508e84d6a328 Mon Sep 17 00:00:00 2001
From: Cody P Schafer <cody@linux.vnet.ibm.com>
Date: Fri, 14 Feb 2014 14:02:07 -0800
Subject: sysfs: create bin_attributes under the requested group
bin_attributes created/updated in create_files() (such as those listed
via (struct device).attribute_groups) were not placed under the
specified group, and instead appeared in the base kobj directory.
Fix this by making bin_attributes use creating code similar to normal
attributes.
A quick grep shows that no one is using bin_attrs in a named attribute
group yet, so we can do this without breaking anything in usespace.
Note that I do not add is_visible() support to
bin_attributes, though that could be done as well.
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/sysfs/group.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
(limited to 'fs')
diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index 6b579387c67a..aa0406895b53 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -70,8 +70,11 @@ static int create_files(struct kernfs_node *parent, struct kobject *kobj,
if (grp->bin_attrs) {
for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++) {
if (update)
- sysfs_remove_bin_file(kobj, *bin_attr);
- error = sysfs_create_bin_file(kobj, *bin_attr);
+ kernfs_remove_by_name(parent,
+ (*bin_attr)->attr.name);
+ error = sysfs_add_file_mode_ns(parent,
+ &(*bin_attr)->attr, true,
+ (*bin_attr)->attr.mode, NULL);
if (error)
break;
}
--
cgit v1.2.3
From 88391d49abb7d8dee91d405f96bd9e003cb6798d Mon Sep 17 00:00:00 2001
From: Richard Cochran <richardcochran@gmail.com>
Date: Wed, 5 Mar 2014 17:10:52 +0100
Subject: kernfs: fix off by one error.
The hash values 0 and 1 are reserved for magic directory entries, but
the code only prevents names hashing to 0. This patch fixes the test
to also prevent hash value 1.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'fs')
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 8245d3b34894..0bd05ab26003 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -190,7 +190,7 @@ static unsigned int kernfs_name_hash(const char *name, const void *ns)
hash = (end_name_hash(hash) ^ hash_ptr((void *)ns, 31));
hash &= 0x7fffffffU;
/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
- if (hash < 1)
+ if (hash < 2)
hash += 2;
if (hash >= INT_MAX)
hash = INT_MAX - 1;
--
cgit v1.2.3
From b7ce40cff0b9f6597f8318fd761accd92727f61f Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 4 Mar 2014 15:38:46 -0500
Subject: kernfs: cache atomic_write_len in kernfs_open_file
While implementing atomic_write_len, 4d3773c4bb41 ("kernfs: implement
kernfs_ops->atomic_write_len") moved data copy from userland inside
kernfs_get_active() and kernfs_open_file->mutex so that
kernfs_ops->atomic_write_len can be accessed before copying buffer
from userland; unfortunately, this could lead to locking order
inversion involving mmap_sem if copy_from_user() takes a page fault.
======================================================
[ INFO: possible circular locking dependency detected ]
3.14.0-rc4-next-20140228-sasha-00011-g4077c67-dirty #26 Tainted: G W
-------------------------------------------------------
trinity-c236/10658 is trying to acquire lock:
(&of->mutex#2){+.+.+.}, at: [<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<mm/util.c:397>] vm_mmap_pgoff+0x6e/0xe0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){++++++}:
[<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
[<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
[<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
[<mm/memory.c:4188>] might_fault+0x7e/0xb0
[<arch/x86/include/asm/uaccess.h:713 fs/kernfs/file.c:291>] kernfs_fop_write+0xd8/0x190
[<fs/read_write.c:473>] vfs_write+0xe3/0x1d0
[<fs/read_write.c:523 fs/read_write.c:515>] SyS_write+0x5d/0xa0
[<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2
-> #0 (&of->mutex#2){+.+.+.}:
[<kernel/locking/lockdep.c:1840>] check_prev_add+0x13f/0x560
[<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
[<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
[<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
[<kernel/locking/mutex.c:470 kernel/locking/mutex.c:571>] mutex_lock_nested+0x6a/0x510
[<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120
[<mm/mmap.c:1573>] mmap_region+0x310/0x5c0
[<mm/mmap.c:1365>] do_mmap_pgoff+0x385/0x430
[<mm/util.c:399>] vm_mmap_pgoff+0x8f/0xe0
[<mm/mmap.c:1416 mm/mmap.c:1374>] SyS_mmap_pgoff+0x1b0/0x210
[<arch/x86/kernel/sys_x86_64.c:72>] SyS_mmap+0x1d/0x20
[<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(&of->mutex#2);
lock(&mm->mmap_sem);
lock(&of->mutex#2);
*** DEADLOCK ***
1 lock held by trinity-c236/10658:
#0: (&mm->mmap_sem){++++++}, at: [<mm/util.c:397>] vm_mmap_pgoff+0x6e/0xe0
stack backtrace:
CPU: 2 PID: 10658 Comm: trinity-c236 Tainted: G W 3.14.0-rc4-next-20140228-sasha-00011-g4077c67-dirty #26
0000000000000000 ffff88011911fa48 ffffffff8438e945 0000000000000000
0000000000000000 ffff88011911fa98 ffffffff811a0109 ffff88011911fab8
ffff88011911fab8 ffff88011911fa98 ffff880119128cc0 ffff880119128cf8
Call Trace:
[<lib/dump_stack.c:52>] dump_stack+0x52/0x7f
[<kernel/locking/lockdep.c:1213>] print_circular_bug+0x129/0x160
[<kernel/locking/lockdep.c:1840>] check_prev_add+0x13f/0x560
[<include/linux/spinlock.h:343 mm/slub.c:1933>] ? deactivate_slab+0x511/0x550
[<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
[<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
[<mm/mmap.c:1552>] ? mmap_region+0x24a/0x5c0
[<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
[<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
[<kernel/locking/mutex.c:470 kernel/locking/mutex.c:571>] mutex_lock_nested+0x6a/0x510
[<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
[<kernel/sched/core.c:2477>] ? get_parent_ip+0x11/0x50
[<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
[<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120
[<mm/mmap.c:1573>] mmap_region+0x310/0x5c0
[<mm/mmap.c:1365>] do_mmap_pgoff+0x385/0x430
[<mm/util.c:397>] ? vm_mmap_pgoff+0x6e/0xe0
[<mm/util.c:399>] vm_mmap_pgoff+0x8f/0xe0
[<kernel/rcu/update.c:97>] ? __rcu_read_unlock+0x44/0xb0
[<fs/file.c:641>] ? dup_fd+0x3c0/0x3c0
[<mm/mmap.c:1416 mm/mmap.c:1374>] SyS_mmap_pgoff+0x1b0/0x210
[<arch/x86/kernel/sys_x86_64.c:72>] SyS_mmap+0x1d/0x20
[<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2
Fix it by caching atomic_write_len in kernfs_open_file during open so
that it can be determined without accessing kernfs_ops in
kernfs_fop_write(). This restores the structure of kernfs_fop_write()
before 4d3773c4bb41 with updated @len determination logic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
References: http://lkml.kernel.org/g/53113485.2090407@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/file.c | 63 +++++++++++++++++++++++++-------------------------
include/linux/kernfs.h | 1 +
2 files changed, 33 insertions(+), 31 deletions(-)
(limited to 'fs')
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index ddcb471b9cc9..8034706a7af8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -253,55 +253,50 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
{
struct kernfs_open_file *of = kernfs_of(file);
const struct kernfs_ops *ops;
- char *buf = NULL;
- ssize_t len;
-
- /*
- * @of->mutex nests outside active ref and is just to ensure that
- * the ops aren't called concurrently for the same open file.
- */
- mutex_lock(&of->mutex);
- if (!kernfs_get_active(of->kn)) {
- mutex_unlock(&of->mutex);
- return -ENODEV;
- }
-
- ops = kernfs_ops(of->kn);
- if (!ops->write) {
- len = -EINVAL;
- goto out_unlock;
- }
+ size_t len;
+ char *buf;
- if (ops->atomic_write_len) {
+ if (of->atomic_write_len) {
len = count;
- if (len > ops->atomic_write_len) {
- len = -E2BIG;
- goto out_unlock;
- }
+ if (len > of->atomic_write_len)
+ return -E2BIG;
} else {
len = min_t(size_t, count, PAGE_SIZE);
}
buf = kmalloc(len + 1, GFP_KERNEL);
- if (!buf) {
- len = -ENOMEM;
- goto out_unlock;
- }
+ if (!buf)
+ return -ENOMEM;
if (copy_from_user(buf, user_buf, len)) {
len = -EFAULT;
- goto out_unlock;
+ goto out_free;
}
buf[len] = '\0'; /* guarantee string termination */
- len = ops->write(of, buf, len, *ppos);
-out_unlock:
+ /*
+ * @of->mutex nests outside active ref and is just to ensure that
+ * the ops aren't called concurrently for the same open file.
+ */
+ mutex_lock(&of->mutex);
+ if (!kernfs_get_active(of->kn)) {
+ mutex_unlock(&of->mutex);
+ len = -ENODEV;
+ goto out_free;
+ }
+
+ ops = kernfs_ops(of->kn);
+ if (ops->write)
+ len = ops->write(of, buf, len, *ppos);
+ else
+ len = -EINVAL;
+
kernfs_put_active(of->kn);
mutex_unlock(&of->mutex);
if (len > 0)
*ppos += len;
-
+out_free:
kfree(buf);
return len;
}
@@ -665,6 +660,12 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
of->kn = kn;
of->file = file;
+ /*
+ * Write path needs to atomic_write_len outside active reference.
+ * Cache it in open_file. See kernfs_fop_write() for details.
+ */
+ of->atomic_write_len = ops->atomic_write_len;
+
/*
* Always instantiate seq_file even if read access doesn't use
* seq_file or is not requested. This unifies private data access
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 09669d092748..b0122dc6f96a 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -158,6 +158,7 @@ struct kernfs_open_file {
int event;
struct list_head list;
+ size_t atomic_write_len;
bool mmapped;
const struct vm_operations_struct *vm_ops;
};
--
cgit v1.2.3
From 72099304eeb316c4b00df3ae83efe4375729bd78 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Tue, 25 Mar 2014 20:54:57 -0700
Subject: Revert "sysfs, driver-core: remove unused
{sysfs|device}_schedule_callback_owner()"
This reverts commit d1ba277e79889085a2faec3b68b91ce89c63f888.
As reported by Stephen, this patch breaks linux-next as a ppc patch
suddenly (after 2 years) started using this old api call. So revert it
for now, it will go away in 3.15-rc2 when we can change the PPC call to
the new api.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/core.c | 33 ++++++++++++++++++
fs/sysfs/file.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/device.h | 11 +++++-
include/linux/sysfs.h | 9 +++++
4 files changed, 144 insertions(+), 1 deletion(-)
(limited to 'fs')
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 20da3ad1696b..0dd65281cc65 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -614,6 +614,39 @@ void device_remove_bin_file(struct device *dev,
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);
+/**
+ * device_schedule_callback_owner - helper to schedule a callback for a device
+ * @dev: device.
+ * @func: callback function to invoke later.
+ * @owner: module owning the callback routine
+ *
+ * Attribute methods must not unregister themselves or their parent device
+ * (which would amount to the same thing). Attempts to do so will deadlock,
+ * since unregistration is mutually exclusive with driver callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @dev as its
+ * argument in the workqueue's process context. @dev will be pinned until
+ * @func returns.
+ *
+ * This routine is usually called via the inline device_schedule_callback(),
+ * which automatically sets @owner to THIS_MODULE.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated, -ENODEV if a reference to @owner isn't available.
+ *
+ * NOTE: This routine won't work if CONFIG_SYSFS isn't set! It uses an
+ * underlying sysfs routine (since it is intended for use by attribute
+ * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
+ */
+int device_schedule_callback_owner(struct device *dev,
+ void (*func)(struct device *), struct module *owner)
+{
+ return sysfs_schedule_callback(&dev->kobj,
+ (void (*)(void *)) func, dev, owner);
+}
+EXPORT_SYMBOL_GPL(device_schedule_callback_owner);
+
static void klist_children_get(struct klist_node *n)
{
struct device_private *p = to_device_private_parent(n);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 28cc1acd5439..1b8b91b67fdb 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -453,3 +453,95 @@ void sysfs_remove_bin_file(struct kobject *kobj,
kernfs_remove_by_name(kobj->sd, attr->attr.name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
+
+struct sysfs_schedule_callback_struct {
+ struct list_head workq_list;
+ struct kobject *kobj;
+ void (*func)(void *);
+ void *data;
+ struct module *owner;
+ struct work_struct work;
+};
+
+static struct workqueue_struct *sysfs_workqueue;
+static DEFINE_MUTEX(sysfs_workq_mutex);
+static LIST_HEAD(sysfs_workq);
+static void sysfs_schedule_callback_work(struct work_struct *work)
+{
+ struct sysfs_schedule_callback_struct *ss = container_of(work,
+ struct sysfs_schedule_callback_struct, work);
+
+ (ss->func)(ss->data);
+ kobject_put(ss->kobj);
+ module_put(ss->owner);
+ mutex_lock(&sysfs_workq_mutex);
+ list_del(&ss->workq_list);
+ mutex_unlock(&sysfs_workq_mutex);
+ kfree(ss);
+}
+
+/**
+ * sysfs_schedule_callback - helper to schedule a callback for a kobject
+ * @kobj: object we're acting for.
+ * @func: callback function to invoke later.
+ * @data: argument to pass to @func.
+ * @owner: module owning the callback code
+ *
+ * sysfs attribute methods must not unregister themselves or their parent
+ * kobject (which would amount to the same thing). Attempts to do so will
+ * deadlock, since unregistration is mutually exclusive with driver
+ * callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @data as its
+ * argument in the workqueue's process context. @kobj will be pinned
+ * until @func returns.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated, -ENODEV if a reference to @owner isn't available,
+ * -EAGAIN if a callback has already been scheduled for @kobj.
+ */
+int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
+ void *data, struct module *owner)
+{
+ struct sysfs_schedule_callback_struct *ss, *tmp;
+
+ if (!try_module_get(owner))
+ return -ENODEV;
+
+ mutex_lock(&sysfs_workq_mutex);
+ list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
+ if (ss->kobj == kobj) {
+ module_put(owner);
+ mutex_unlock(&sysfs_workq_mutex);
+ return -EAGAIN;
+ }
+ mutex_unlock(&sysfs_workq_mutex);
+
+ if (sysfs_workqueue == NULL) {
+ sysfs_workqueue = create_singlethread_workqueue("sysfsd");
+ if (sysfs_workqueue == NULL) {
+ module_put(owner);
+ return -ENOMEM;
+ }
+ }
+
+ ss = kmalloc(sizeof(*ss), GFP_KERNEL);
+ if (!ss) {
+ module_put(owner);
+ return -ENOMEM;
+ }
+ kobject_get(kobj);
+ ss->kobj = kobj;
+ ss->func = func;
+ ss->data = data;
+ ss->owner = owner;
+ INIT_WORK(&ss->work, sysfs_schedule_callback_work);
+ INIT_LIST_HEAD(&ss->workq_list);
+ mutex_lock(&sysfs_workq_mutex);
+ list_add_tail(&ss->workq_list, &sysfs_workq);
+ mutex_unlock(&sysfs_workq_mutex);
+ queue_work(sysfs_workqueue, &ss->work);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_schedule_callback);
diff --git a/include/linux/device.h b/include/linux/device.h
index fb1ba13f7665..1ff3f1697513 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -566,6 +566,12 @@ extern int __must_check device_create_bin_file(struct device *dev,
const struct bin_attribute *attr);
extern void device_remove_bin_file(struct device *dev,
const struct bin_attribute *attr);
+extern int device_schedule_callback_owner(struct device *dev,
+ void (*func)(struct device *dev), struct module *owner);
+
+/* This is a macro to avoid include problems with THIS_MODULE */
+#define device_schedule_callback(dev, func) \
+ device_schedule_callback_owner(dev, func, THIS_MODULE)
/* device resource management */
typedef void (*dr_release_t)(struct device *dev, void *res);
@@ -925,7 +931,10 @@ extern int device_online(struct device *dev);
extern struct device *__root_device_register(const char *name,
struct module *owner);
-/* This is a macro to avoid include problems with THIS_MODULE */
+/*
+ * This is a macro to avoid include problems with THIS_MODULE,
+ * just as per what is done for device_schedule_callback() above.
+ */
#define root_device_register(name) \
__root_device_register(name, THIS_MODULE)
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index fdaa0c6fc7a2..e0bf210ddffd 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -178,6 +178,9 @@ struct sysfs_ops {
#ifdef CONFIG_SYSFS
+int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
+ void *data, struct module *owner);
+
int __must_check sysfs_create_dir_ns(struct kobject *kobj, const void *ns);
void sysfs_remove_dir(struct kobject *kobj);
int __must_check sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
@@ -251,6 +254,12 @@ static inline void sysfs_enable_ns(struct kernfs_node *kn)
#else /* CONFIG_SYSFS */
+static inline int sysfs_schedule_callback(struct kobject *kobj,
+ void (*func)(void *), void *data, struct module *owner)
+{
+ return -ENOSYS;
+}
+
static inline int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
{
return 0;
--
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