From: Lars Ellenberg <lars.ellenberg@linbit.com>
Date: Wed, 1 Sep 2010 13:12:12 +0000 (+0200)
Subject: drbd: fix race on meta-data update
X-Git-Tag: firefly_0821_release~7613^2~3690^2~35
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3f3a9b849d2b703934c07fa17f5eac2dc37c1f6b;p=firefly-linux-kernel-4.4.55.git

drbd: fix race on meta-data update

The race:
	drbd_md_mark_dirty()
	drbd_md_sync()
		if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
			return;
		drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)
  ==> RACE
		clear_bit(MD_DIRTY, &mdev->flags); <== spurious

Fixed by removing the spurious clear_bit.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
---

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 23878ffc43c8..73c905d0ef18 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3446,12 +3446,9 @@ void drbd_md_sync(struct drbd_conf *mdev)
 	D_ASSERT(drbd_md_ss__(mdev, mdev->ldev) == mdev->ldev->md.md_offset);
 	sector = mdev->ldev->md.md_offset;
 
-	if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
-		clear_bit(MD_DIRTY, &mdev->flags);
-	} else {
+	if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
 		/* this was a try anyways ... */
 		dev_err(DEV, "meta data update failed!\n");
-
 		drbd_chk_io_error(mdev, 1, TRUE);
 	}