[PATCH] autofs4: wait order fix

It's possible for an event wait request to arive before the event
requestor.  If this happens the daemon never gets notified and autofs
hangs.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 13 insertions, 10 deletions

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index f5a52c871726..978987735252 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -84,6 +84,7 @@ struct autofs_wait_queue {
         char *name;
         /* This is for status reporting upon return */
         int status;
+        atomic_t notified;
         atomic_t wait_ctr;
 };
 
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index 1ab24a662e09..5a40d36e5a51 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -210,17 +210,8 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
                 wq->len = len;
                 wq->status = -EINTR; /* Status return if interrupted */
                 atomic_set(&wq->wait_ctr, 2);
+                atomic_set(&wq->notified, 1);
                 up(&sbi->wq_sem);
-
-                DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d",
-                        (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
-                /* autofs4_notify_daemon() may block */
-                if (notify != NFY_NONE) {
-                        autofs4_notify_daemon(sbi,wq, 
-                                        notify == NFY_MOUNT ?
-                                                  autofs_ptype_missing :
-                                                  autofs_ptype_expire_multi);
-                }
         } else {
                 atomic_inc(&wq->wait_ctr);
                 up(&sbi->wq_sem);
@@ -229,6 +220,17 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
         }
 
+        if (notify != NFY_NONE && atomic_dec_and_test(&wq->notified)) {
+                int type = (notify == NFY_MOUNT ?
+                        autofs_ptype_missing : autofs_ptype_expire_multi);
+
+                DPRINTK(("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
+                        (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify));
+
+                /* autofs4_notify_daemon() may block */
+                autofs4_notify_daemon(sbi, wq, type);
+        }
+
         /* wq->name is NULL if and only if the lock is already released */
 
         if ( sbi->catatonic ) {