sysfs: use iget_locked() instead of new_inode()

After dentry is reclaimed, sysfs always used to allocate new dentry
and inode if the file is accessed again.  This causes problem with
operations which only pin the inode.  For example, if inotify watch is
added to a sysfs file and the dentry for the file is reclaimed, the
next update event creates new dentry and new inode making the inotify
watch miss all the events from there on.

This patch fixes it by using iget_locked() instead of new_inode().
sysfs_new_inode() is renamed to sysfs_get_inode() and inode is
initialized iff the inode is newly allocated.  sysfs_instantiate() is
responsible for unlocking new inodes.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 15 insertions, 9 deletions

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 26d8503c8997..3eab9c46a71b 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -153,10 +153,12 @@ void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 }
 
 /**
- *	sysfs_new_inode - allocate new inode for sysfs_dirent
+ *	sysfs_get_inode - get inode for sysfs_dirent
  *	@sd: sysfs_dirent to allocate inode for
  *
- *	Allocate inode for @sd and initialize basics.
+ *	Get inode for @sd.  If such inode doesn't exist, a new inode
+ *	is allocated and basics are initialized.  New inode is
+ *	returned locked.
  *
  *	LOCKING:
  *	Kernel thread context (may sleep).
@@ -164,12 +166,12 @@ void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
  *	RETURNS:
  *	Pointer to allocated inode on success, NULL on failure.
  */
-struct inode * sysfs_new_inode(struct sysfs_dirent *sd)
+struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 {
 	struct inode *inode;
 
-	inode = new_inode(sysfs_sb);
-	if (inode)
+	inode = iget_locked(sysfs_sb, sd->s_ino);
+	if (inode && (inode->i_state & I_NEW))
 		sysfs_init_inode(sd, inode);
 
 	return inode;
@@ -180,7 +182,7 @@ struct inode * sysfs_new_inode(struct sysfs_dirent *sd)
  *	@dentry: dentry to be instantiated
  *	@inode: inode associated with @sd
  *
- *	Instantiate @dentry with @inode.
+ *	Unlock @inode if locked and instantiate @dentry with @inode.
  *
  *	LOCKING:
  *	None.
@@ -189,9 +191,13 @@ void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
 {
 	BUG_ON(!dentry || dentry->d_inode);
 
-	if (dentry->d_parent && dentry->d_parent->d_inode) {
-		struct inode *p_inode = dentry->d_parent->d_inode;
-		p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
+	if (inode->i_state & I_NEW) {
+		unlock_new_inode(inode);
+
+		if (dentry->d_parent && dentry->d_parent->d_inode) {
+			struct inode *p_inode = dentry->d_parent->d_inode;
+			p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
+		}
 	}
 
 	d_instantiate(dentry, inode);