+ autofs4-dont-release-directory-mutex-if-called-in-oz_mode.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     autofs4: don't release directory mutex if called in oz_mode
has been added to the -mm tree.  Its filename is
     autofs4-dont-release-directory-mutex-if-called-in-oz_mode.patch

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------------------------------------------------------
Subject: autofs4: don't release directory mutex if called in oz_mode
From: Ian Kent <raven@themaw.net>

Since we now delay hashing of dentrys until the ->mkdir() call, droping
and re-taking the directory mutex within the ->lookup() function when we
are being called by user space is not needed.  This can lead to a race
when other processes are attempting to access the same directory during
mount point directory creation.

In this case we need to hang onto the mutex to ensure we don't get user
processes trying to create a mount request for a newly created dentry
after the mount point entry has already been created.  This ensures that
when we need to check a dentry passed to autofs4_wait(), if it is hashed,
it is always the mount point dentry and not a new dentry created by
another lookup during directory creation.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/autofs4/root.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff -puN fs/autofs4/root.c~autofs4-dont-release-directory-mutex-if-called-in-oz_mode fs/autofs4/root.c
--- a/fs/autofs4/root.c~autofs4-dont-release-directory-mutex-if-called-in-oz_mode
+++ a/fs/autofs4/root.c
@@ -683,12 +683,11 @@ static struct dentry *autofs4_lookup(str
 		spin_lock(&dentry->d_lock);
 		dentry->d_flags |= DCACHE_AUTOFS_PENDING;
 		spin_unlock(&dentry->d_lock);
-	}