[PATCH] Btrfs: nuke a bogus rw_devices decrement in __btrfs_close_devices

[Ilya Dryomov <idryomov@gmail.com>]

On mount failures, __btrfs_close_devices can be called well before
dev-replace state is read and ->is_tgtdev_for_dev_replace is set.  This
leads to a bogus decrement of ->rw_devices and sets off a WARN_ON in
__btrfs_close_devices if replace target device happens to be on the
lists and we fail early in the mount sequence.  Fix this by checking
the devid instead of ->is_tgtdev_for_dev_replace before the decrement:
for replace targets devid is always equal to BTRFS_DEV_REPLACE_DEVID.

Cc: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 fs/btrfs/volumes.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 043b215..a306db9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -666,7 +666,8 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 		if (device->bdev)
 			fs_devices->open_devices--;
 
-		if (device->writeable && !device->is_tgtdev_for_dev_replace) {
+		if (device->writeable &&
+		    device->devid != BTRFS_DEV_REPLACE_DEVID) {
 			list_del_init(&device->dev_alloc_list);
 			fs_devices->rw_devices--;
 		}
-- 
1.7.10.4