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authorAl Viro <viro@zeniv.linux.org.uk>2017-01-09 22:29:15 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2017-01-09 22:29:15 -0500
commit4675ac39b5dd5ff08dd8cb2be9ddd3cba778aa39 (patch)
treeafbb65c11de564e2567865acaee816ab6e1e130c /fs/namei.c
parenta89f833737e6c75df0091ccf6c767b94745463c1 (diff)
downloadlinux-4675ac39b5dd5ff08dd8cb2be9ddd3cba778aa39.tar.bz2
namei.c: split unlazy_walk()
In all but one case, the last two arguments are NULL and 0 resp.; almost everyone just wants to switch nameidata to non-RCU mode. The only exception is lookup_fast(), where we have a child dentry we want to legitimize as well. Split these two cases. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c105
1 files changed, 66 insertions, 39 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 2ed2701a74b5..76cfeb641e97 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -672,17 +672,15 @@ static bool legitimize_links(struct nameidata *nd)
/**
* unlazy_walk - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
- * @dentry: child of nd->path.dentry or NULL
- * @seq: seq number to check dentry against
* Returns: 0 on success, -ECHILD on failure
*
- * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
- * for ref-walk mode. @dentry must be a path found by a do_lookup call on
- * @nd or NULL. Must be called from rcu-walk context.
+ * unlazy_walk attempts to legitimize the current nd->path and nd->root
+ * for ref-walk mode.
+ * Must be called from rcu-walk context.
* Nothing should touch nameidata between unlazy_walk() failure and
* terminate_walk().
*/
-static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq)
+static int unlazy_walk(struct nameidata *nd)
{
struct dentry *parent = nd->path.dentry;
@@ -691,33 +689,66 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq
nd->flags &= ~LOOKUP_RCU;
if (unlikely(!legitimize_links(nd)))
goto out2;
+ if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
+ goto out1;
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq)))
+ goto out;
+ }
+ rcu_read_unlock();
+ BUG_ON(nd->inode != parent->d_inode);
+ return 0;
+
+out2:
+ nd->path.mnt = NULL;
+ nd->path.dentry = NULL;
+out1:
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
+out:
+ rcu_read_unlock();
+ return -ECHILD;
+}
+
+/**
+ * unlazy_child - try to switch to ref-walk mode.
+ * @nd: nameidata pathwalk data
+ * @dentry: child of nd->path.dentry
+ * @seq: seq number to check dentry against
+ * Returns: 0 on success, -ECHILD on failure
+ *
+ * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
+ * for ref-walk mode. @dentry must be a path found by a do_lookup call on
+ * @nd. Must be called from rcu-walk context.
+ * Nothing should touch nameidata between unlazy_child() failure and
+ * terminate_walk().
+ */
+static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq)
+{
+ BUG_ON(!(nd->flags & LOOKUP_RCU));
+
+ nd->flags &= ~LOOKUP_RCU;
+ if (unlikely(!legitimize_links(nd)))
+ goto out2;
if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
goto out2;
- if (unlikely(!lockref_get_not_dead(&parent->d_lockref)))
+ if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
goto out1;
/*
- * For a negative lookup, the lookup sequence point is the parents
- * sequence point, and it only needs to revalidate the parent dentry.
- *
- * For a positive lookup, we need to move both the parent and the
- * dentry from the RCU domain to be properly refcounted. And the
- * sequence number in the dentry validates *both* dentry counters,
- * since we checked the sequence number of the parent after we got
- * the child sequence number. So we know the parent must still
- * be valid if the child sequence number is still valid.
+ * We need to move both the parent and the dentry from the RCU domain
+ * to be properly refcounted. And the sequence number in the dentry
+ * validates *both* dentry counters, since we checked the sequence
+ * number of the parent after we got the child sequence number. So we
+ * know the parent must still be valid if the child sequence number is
*/
- if (!dentry) {
- if (read_seqcount_retry(&parent->d_seq, nd->seq))
- goto out;
- BUG_ON(nd->inode != parent->d_inode);
- } else {
- if (!lockref_get_not_dead(&dentry->d_lockref))
- goto out;
- if (read_seqcount_retry(&dentry->d_seq, seq))
- goto drop_dentry;
+ if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
+ goto out;
+ if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) {
+ rcu_read_unlock();
+ dput(dentry);
+ goto drop_root_mnt;
}
-
/*
* Sequence counts matched. Now make sure that the root is
* still valid and get it if required.
@@ -733,10 +764,6 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq
rcu_read_unlock();
return 0;
-drop_dentry:
- rcu_read_unlock();
- dput(dentry);
- goto drop_root_mnt;
out2:
nd->path.mnt = NULL;
out1:
@@ -775,7 +802,7 @@ static int complete_walk(struct nameidata *nd)
if (nd->flags & LOOKUP_RCU) {
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
- if (unlikely(unlazy_walk(nd, NULL, 0)))
+ if (unlikely(unlazy_walk(nd)))
return -ECHILD;
}
@@ -1001,7 +1028,7 @@ const char *get_link(struct nameidata *nd)
touch_atime(&last->link);
cond_resched();
} else if (atime_needs_update_rcu(&last->link, inode)) {
- if (unlikely(unlazy_walk(nd, NULL, 0)))
+ if (unlikely(unlazy_walk(nd)))
return ERR_PTR(-ECHILD);
touch_atime(&last->link);
}
@@ -1020,7 +1047,7 @@ const char *get_link(struct nameidata *nd)
if (nd->flags & LOOKUP_RCU) {
res = get(NULL, inode, &last->done);
if (res == ERR_PTR(-ECHILD)) {
- if (unlikely(unlazy_walk(nd, NULL, 0)))
+ if (unlikely(unlazy_walk(nd)))
return ERR_PTR(-ECHILD);
res = get(dentry, inode, &last->done);
}
@@ -1529,7 +1556,7 @@ static int lookup_fast(struct nameidata *nd,
bool negative;
dentry = __d_lookup_rcu(parent, &nd->last, &seq);
if (unlikely(!dentry)) {
- if (unlazy_walk(nd, NULL, 0))
+ if (unlazy_walk(nd))
return -ECHILD;
return 0;
}
@@ -1567,7 +1594,7 @@ static int lookup_fast(struct nameidata *nd,
if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
return 1;
}
- if (unlazy_walk(nd, dentry, seq))
+ if (unlazy_child(nd, dentry, seq))
return -ECHILD;
if (unlikely(status == -ECHILD))
/* we'd been told to redo it in non-rcu mode */
@@ -1646,7 +1673,7 @@ static inline int may_lookup(struct nameidata *nd)
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
if (err != -ECHILD)
return err;
- if (unlazy_walk(nd, NULL, 0))
+ if (unlazy_walk(nd))
return -ECHILD;
}
return inode_permission(nd->inode, MAY_EXEC);
@@ -1690,7 +1717,7 @@ static int pick_link(struct nameidata *nd, struct path *link,
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
- } else if (likely(unlazy_walk(nd, NULL, 0)) == 0)
+ } else if (likely(unlazy_walk(nd)) == 0)
error = nd_alloc_stack(nd);
}
if (error) {
@@ -2108,7 +2135,7 @@ OK:
}
if (unlikely(!d_can_lookup(nd->path.dentry))) {
if (nd->flags & LOOKUP_RCU) {
- if (unlazy_walk(nd, NULL, 0))
+ if (unlazy_walk(nd))
return -ECHILD;
}
return -ENOTDIR;
@@ -2565,7 +2592,7 @@ mountpoint_last(struct nameidata *nd)
/* If we're in rcuwalk, drop out of it to handle last component */
if (nd->flags & LOOKUP_RCU) {
- if (unlazy_walk(nd, NULL, 0))
+ if (unlazy_walk(nd))
return -ECHILD;
}