nilfs2: integrate sysfs support into driver

This patch integrates creation of sysfs groups and
attributes into NILFS file system driver.

It was found the issue with nilfs_sysfs_{create/delete}_snapshot_group
functions by Michael L Semon <mlsemon35@gmail.com> in the first
version of the patch:

  BUG: sleeping function called from invalid context at kernel/locking/mutex.c:579
  in_atomic(): 1, irqs_disabled(): 0, pid: 32676, name: umount.nilfs2
  2 locks held by umount.nilfs2/32676:
   #0:  (&type->s_umount_key#21){++++..}, at: [<790c18e2>] deactivate_super+0x37/0x58
   #1:  (&(&nilfs->ns_cptree_lock)->rlock){+.+...}, at: [<791bf659>] nilfs_put_root+0x23/0x5a
  Preemption disabled at:[<791bf659>] nilfs_put_root+0x23/0x5a

  CPU: 0 PID: 32676 Comm: umount.nilfs2 Not tainted 3.14.0+ #2
  Hardware name: Dell Computer Corporation Dimension 2350/07W080, BIOS A01 12/17/2002
  Call Trace:
    dump_stack+0x4b/0x75
    __might_sleep+0x111/0x16f
    mutex_lock_nested+0x1e/0x3ad
    kernfs_remove+0x12/0x26
    sysfs_remove_dir+0x3d/0x62
    kobject_del+0x13/0x38
    nilfs_sysfs_delete_snapshot_group+0xb/0xd
    nilfs_put_root+0x2a/0x5a
    nilfs_detach_log_writer+0x1ab/0x2c1
    nilfs_put_super+0x13/0x68
    generic_shutdown_super+0x60/0xd1
    kill_block_super+0x1d/0x60
    deactivate_locked_super+0x22/0x3f
    deactivate_super+0x3e/0x58
    mntput_no_expire+0xe2/0x141
    SyS_oldumount+0x70/0xa5
    syscall_call+0x7/0xb

The reason of the issue was placement of
nilfs_sysfs_{create/delete}_snapshot_group() call under
nilfs->ns_cptree_lock protection.  But this protection is unnecessary and
wrong solution.  The second version of the patch fixes this issue.

[fengguang.wu@intel.com: nilfs_sysfs_create_mounted_snapshots_group can be static]
Reported-by: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Vyacheslav Dubeyko <Vyacheslav.Dubeyko@hgst.com>
Cc: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 59d50088b886..9da25fe9ea61 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -98,6 +98,7 @@ void destroy_nilfs(struct the_nilfs *nilfs)
 {
 	might_sleep();
 	if (nilfs_init(nilfs)) {
+		nilfs_sysfs_delete_device_group(nilfs);
 		brelse(nilfs->ns_sbh[0]);
 		brelse(nilfs->ns_sbh[1]);
 	}
@@ -641,6 +642,10 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)
 	if (err)
 		goto failed_sbh;
 
+	err = nilfs_sysfs_create_device_group(sb);
+	if (err)
+		goto failed_sbh;
+
 	set_nilfs_init(nilfs);
 	err = 0;
  out:
@@ -741,12 +746,13 @@ nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
 {
 	struct rb_node **p, *parent;
 	struct nilfs_root *root, *new;
+	int err;
 
 	root = nilfs_lookup_root(nilfs, cno);
 	if (root)
 		return root;
 
-	new = kmalloc(sizeof(*root), GFP_KERNEL);
+	new = kzalloc(sizeof(*root), GFP_KERNEL);
 	if (!new)
 		return NULL;
 
@@ -783,6 +789,12 @@ nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
 
 	spin_unlock(&nilfs->ns_cptree_lock);
 
+	err = nilfs_sysfs_create_snapshot_group(new);
+	if (err) {
+		kfree(new);
+		new = NULL;
+	}
+
 	return new;
 }
 
@@ -791,6 +803,8 @@ void nilfs_put_root(struct nilfs_root *root)
 	if (atomic_dec_and_test(&root->count)) {
 		struct the_nilfs *nilfs = root->nilfs;
 
+		nilfs_sysfs_delete_snapshot_group(root);
+
 		spin_lock(&nilfs->ns_cptree_lock);
 		rb_erase(&root->rb_node, &nilfs->ns_cptree);
 		spin_unlock(&nilfs->ns_cptree_lock);