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>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index 2ba44c79d548..e16980b00b8d 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -225,6 +225,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
         sbi->min_proto = 0;
         sbi->max_proto = 0;
         mutex_init(&sbi->wq_mutex);
+        mutex_init(&sbi->pipe_mutex);
         spin_lock_init(&sbi->fs_lock);
         sbi->queues = NULL;
         spin_lock_init(&sbi->lookup_lock);