From: Miklos Szeredi <mszeredi@xxxxxxx>
IBM reported a soft lockup after applying the fix for the rename_lock deadlock.
Commit c83ce989 ("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@xxxxxxx>
Cc: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
fs/dcache.c | 4 ++--
include/linux/dcache.h | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c 2012-09-17 20:04:07.000000000 +0200
+++ linux-2.6/fs/dcache.c 2012-09-17 20:04:21.000000000 +0200
@@ -389,7 +389,7 @@ static struct dentry *d_kill(struct dent
* 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(stru
* 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;
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h 2012-09-17 19:56:19.000000000 +0200
+++ linux-2.6/include/linux/dcache.h 2012-09-17 20:04:21.000000000 +0200
@@ -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)
--
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