Subject: + autofs-fix-lockref-lookup.patch added to -mm tree
To: raven@xxxxxxxxxx,torvalds@xxxxxxxxxxxxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 23 Apr 2014 14:46:46 -0700
The patch titled
Subject: autofs: fix lockref lookup
has been added to the -mm tree. Its filename is
autofs-fix-lockref-lookup.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/autofs-fix-lockref-lookup.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/autofs-fix-lockref-lookup.patch
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From: Ian Kent <raven@xxxxxxxxxx>
Subject: autofs: fix lockref lookup
autofs needs to be able to see private data dentry flags for its dentrys
that are being created but not yet hashed and for its dentrys that have
been rmdir()ed but not yet freed. It needs to do this so it can block
processes in these states until a status has been returned to indicate the
given operation is complete.
It does this by keeping two lists, active and expring, of dentrys in this
state and uses ->d_release() to keep them stable while it checks the
reference count to determine if they should be used.
But with the recent lockref changes dentrys being freed sometimes don't
transition to a reference count of 0 before being freed so autofs can
occassionally use a dentry that is invalid which can lead to a panic.
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/autofs4/root.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN fs/autofs4/root.c~autofs-fix-lockref-lookup fs/autofs4/root.c
--- a/fs/autofs4/root.c~autofs-fix-lockref-lookup
+++ a/fs/autofs4/root.c
@@ -179,7 +179,7 @@ static struct dentry *autofs4_lookup_act
spin_lock(&active->d_lock);
/* Already gone? */
- if (!d_count(active))
+ if ((int) d_count(active) <= 0)
goto next;
qstr = &active->d_name;
@@ -230,7 +230,7 @@ static struct dentry *autofs4_lookup_exp
spin_lock(&expiring->d_lock);
- /* Bad luck, we've already been dentry_iput */
+ /* We've already been dentry_iput or unlinked */
if (!expiring->d_inode)
goto next;
_
Patches currently in -mm which might be from raven@xxxxxxxxxx are
autofs-fix-lockref-lookup.patch
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