fuse: fix possibly missed wake-up after abort

[sfrench/cifs-2.6.git] / fs / fuse / dev.c

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6fe330cc970915de6d0305be6d016e6376a3639e..a5e516a40e7a359cdae8b2bf289175e971b6e6c9 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -165,9 +165,13 @@ static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
 
 static void fuse_drop_waiting(struct fuse_conn *fc)
 {
-       if (fc->connected) {
-               atomic_dec(&fc->num_waiting);
-       } else if (atomic_dec_and_test(&fc->num_waiting)) {
+       /*
+        * lockess check of fc->connected is okay, because atomic_dec_and_test()
+        * provides a memory barrier mached with the one in fuse_wait_aborted()
+        * to ensure no wake-up is missed.
+        */
+       if (atomic_dec_and_test(&fc->num_waiting) &&
+           !READ_ONCE(fc->connected)) {
                /* wake up aborters */
                wake_up_all(&fc->blocked_waitq);
        }
@@ -2221,6 +2225,8 @@ EXPORT_SYMBOL_GPL(fuse_abort_conn);
 
 void fuse_wait_aborted(struct fuse_conn *fc)
 {
+       /* matches implicit memory barrier in fuse_drop_waiting() */
+       smp_mb();
        wait_event(fc->blocked_waitq, atomic_read(&fc->num_waiting) == 0);
 }