[PATCH 4.13 095/110] md: fix a race condition for flush request handling

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shaohua Li <shli@xxxxxx>

commit 79bf31a3b2a7ca467cfec8ff97d359a77065d01f upstream.

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@xxxxxxxxxxx>
Tested-by: Nate Dailey <nate.dailey@xxxxxxxxxxx>
Fix: cc27b0c78c79(md: fix deadlock between mddev_suspend() and md_write_start())
Reviewed-by: NeilBrown <neilb@xxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/md.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -439,16 +439,22 @@ static void md_submit_flush_data(struct
 	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)