md: fix a race condition for flush request handling

md_submit_flush_data calls pers->make_request, which missed the suspend check.
Fix it with the new md_handle_request API.

Reported-by: Nate Dailey <nate.dailey@stratus.com>
Tested-by: Nate Dailey <nate.dailey@stratus.com>
Fix: cc27b0c78c79(md: fix deadlock between mddev_suspend() and md_write_start())
Cc: stable@vger.kernel.org
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1db1a22..0ff1bbf 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -447,16 +447,22 @@ static void md_submit_flush_data(struct work_struct *ws)
        struct mddev *mddev = container_of(ws, struct mddev, flush_work);
        struct bio *bio = mddev->flush_bio;
 
+       /*
+        * must reset flush_bio before calling into md_handle_request to avoid a
+        * deadlock, because other bios passed md_handle_request suspend check
+        * could wait for this and below md_handle_request could wait for those
+        * bios because of suspend check
+        */
+       mddev->flush_bio = NULL;
+       wake_up(&mddev->sb_wait);
+
        if (bio->bi_iter.bi_size == 0)
                /* an empty barrier - all done */
                bio_endio(bio);
        else {
                bio->bi_opf &= ~REQ_PREFLUSH;
-               mddev->pers->make_request(mddev, bio);
+               md_handle_request(mddev, bio);
        }
-
-       mddev->flush_bio = NULL;
-       wake_up(&mddev->sb_wait);
 }
 
 void md_flush_request(struct mddev *mddev, struct bio *bio)