autofs4: deal with autofs4_write/autofs4_write races
Just serialize the actual writing of packets into pipe on
a new mutex, independent from everything else in the locking
hierarchy. As soon as something has started feeding a piece
of packet into the pipe to daemon, we *want* everything else
about to try the same to wait until we are done.
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 5869d4e..d8d8e7b 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -116,6 +116,7 @@
int needs_reghost;
struct super_block *sb;
struct mutex wq_mutex;
+ struct mutex pipe_mutex;
spinlock_t fs_lock;
struct autofs_wait_queue *queues; /* Wait queue pointer */
spinlock_t lookup_lock;