btrfs: make BTRFS_RESERVE_FLUSH_EVICT use the global rsv stealing code

I forgot to convert this over when I introduced the global reserve
stealing code to the space flushing code.  Evict was simply trying to
make its reservation and then if it failed it would steal from the
global rsv, which is racey because it's outside of the normal ticketing
code.

Fix this by setting ticket->steal if we are BTRFS_RESERVE_FLUSH_EVICT,
and then make the priority flushing path do the steal for us.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 6 insertions, 9 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e87c6cccf045..0b89704f7e21 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5523,7 +5523,6 @@ static struct btrfs_trans_handle *evict_refill_and_join(struct btrfs_root *root,
 							struct btrfs_block_rsv *rsv)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
 	struct btrfs_trans_handle *trans;
 	u64 delayed_refs_extra = btrfs_calc_insert_metadata_size(fs_info, 1);
 	int ret;
@@ -5538,18 +5537,16 @@ static struct btrfs_trans_handle *evict_refill_and_join(struct btrfs_root *root,
 	 * above.  We reserve our extra bit here because we generate a ton of
 	 * delayed refs activity by truncating.
 	 *
-	 * If we cannot make our reservation we'll attempt to steal from the
-	 * global reserve, because we really want to be able to free up space.
+	 * BTRFS_RESERVE_FLUSH_EVICT will steal from the global_rsv if it can,
+	 * if we fail to make this reservation we can re-try without the
+	 * delayed_refs_extra so we can make some forward progress.
 	 */
 	ret = btrfs_block_rsv_refill(root, rsv, rsv->size + delayed_refs_extra,
 				     BTRFS_RESERVE_FLUSH_EVICT);
 	if (ret) {
-		/*
-		 * Try to steal from the global reserve if there is space for
-		 * it.
-		 */
-		if (btrfs_check_space_for_delayed_refs(fs_info) ||
-		    btrfs_block_rsv_migrate(global_rsv, rsv, rsv->size, 0)) {
+		ret = btrfs_block_rsv_refill(root, rsv, rsv->size,
+					     BTRFS_RESERVE_FLUSH_EVICT);
+		if (ret) {
 			btrfs_warn(fs_info,
 				   "could not allocate space for delete; will truncate on mount");
 			return ERR_PTR(-ENOSPC);