vfs: dcache: use DCACHE_DENTRY_KILLED instead of DCACHE_DISCONNECTED in d_kill()
Miklos Szeredi [Mon, 17 Sep 2012 20:31:38 +0000 (22:31 +0200)]
commit b161dfa6937ae46d50adce8a7c6b12233e96e7bd upstream.

IBM reported a soft lockup after applying the fix for the rename_lock
deadlock.  Commit c83ce989cb5f ("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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/dcache.c
include/linux/dcache.h

index b80531c..10fab26 100644 (file)
@@ -373,7 +373,7 @@ 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);
@@ -1030,7 +1030,7 @@ 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;
index 7e11f14..1332df0 100644 (file)
@@ -191,6 +191,8 @@ 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)