[PATCH] Btrfs: update drop progress before stopping snapshot dropping

[Josef Bacik <jbacik@fusionio.com>]

Alex pointed out a problem and fix that exists in the drop one snapshot at a
time patch.  If we decide we need to exit for whatever reason (umount for
example) we will just exit the snapshot dropping without updating the drop
progress.  So the next time we go to resume we will BUG_ON() because we can't
find the extent we left off at because we never updated it.  This patch fixes
the problem.

Cc: stable@vger.kernel.org
Reported-by: Alex Lyakas <alex.btrfs@zadarastorage.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
 fs/btrfs/extent-tree.c |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index bc00b24..8c204e1 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7584,11 +7584,6 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 	wc->reada_count = BTRFS_NODEPTRS_PER_BLOCK(root);
 
 	while (1) {
-		if (!for_reloc && btrfs_need_cleaner_sleep(root)) {
-			pr_debug("btrfs: drop snapshot early exit\n");
-			err = -EAGAIN;
-			goto out_end_trans;
-		}
 
 		ret = walk_down_tree(trans, root, path, wc);
 		if (ret < 0) {
@@ -7616,7 +7611,8 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 		}
 
 		BUG_ON(wc->level == 0);
-		if (btrfs_should_end_transaction(trans, tree_root)) {
+		if (btrfs_should_end_transaction(trans, tree_root) ||
+		    (!for_reloc && btrfs_need_cleaner_sleep(root))) {
 			ret = btrfs_update_root(trans, tree_root,
 						&root->root_key,
 						root_item);
@@ -7627,6 +7623,12 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
 			}
 
 			btrfs_end_transaction_throttle(trans, tree_root);
+			if (!for_reloc && btrfs_need_cleaner_sleep(root)) {
+				pr_debug("btrfs: drop snapshot early exit\n");
+				err = -EAGAIN;
+				goto out_free;
+			}
+
 			trans = btrfs_start_transaction(tree_root, 0);
 			if (IS_ERR(trans)) {
 				err = PTR_ERR(trans);
-- 
1.7.7.6