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vfs: dcache: use DCACHE_DENTRY_KILLED instead of DCACHE_DISCONNECTED in d_kill()

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IBM reported a soft lockup after applying the fix for the rename_lock
deadlock.  Commit c83ce989cb ("VFS: Fix the nfs sillyrename regression
in kernel 2.6.38") was found to be the culprit.

The nfs sillyrename fix used DCACHE_DISCONNECTED to indicate that the
dentry was killed.  This flag can be set on non-killed dentries too,
which results in infinite retries when trying to traverse the dentry
tree.

This patch introduces a separate flag: DCACHE_DENTRY_KILLED, which is
only set in d_kill() and makes try_to_ascend() test only this flag.

IBM reported successful test results with this patch.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miklos Szeredi 2012-09-17 22:31:38 +02:00 • committed by Linus Torvalds
commit b161dfa693
2 changed files with 4 additions and 2 deletions
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4
fs/dcache.c
View file

@ -389,7 +389,7 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
* Inform try_to_ascend() that we are no longer attached to the
* dentry tree
*/
dentry->d_flags |= DCACHE_DISCONNECTED;
dentry->d_flags |= DCACHE_DENTRY_KILLED;
if (parent)
spin_unlock(&parent->d_lock);
dentry_iput(dentry);
@ -1048,7 +1048,7 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq
* or deletion
*/
if (new != old->d_parent ||
(old->d_flags & DCACHE_DISCONNECTED) ||
(old->d_flags & DCACHE_DENTRY_KILLED) ||
(!locked && read_seqretry(&rename_lock, seq))) {
spin_unlock(&new->d_lock);
new = NULL;

2
include/linux/dcache.h
View file

@ -206,6 +206,8 @@ struct dentry_operations {
#define DCACHE_MANAGED_DENTRY \
(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
#define DCACHE_DENTRY_KILLED 0x100000
extern seqlock_t rename_lock;
static inline int dname_external(struct dentry *dentry)