[PATCH v6 04/16] btrfs: remove remapped block groups from the free-space tree

[Mark Harmstone <mark@harmstone.com>]

No new allocations can be done from block groups that have the REMAPPED flag
set, so there's no value in their having entries in the free-space tree.

Prevent a search through the free-space tree being scheduled for such a
block group, and prevent any additions to the in-memory free-space tree.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
Reviewed-by: Boris Burkov <boris@bur.io>
---
 fs/btrfs/block-group.c      | 19 ++++++++++++++++---
 fs/btrfs/free-space-cache.c |  3 +++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index b964eacc1610..0e88e52aa909 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -933,6 +933,13 @@ int btrfs_cache_block_group(struct btrfs_block_group *cache, bool wait)
 	if (btrfs_is_zoned(fs_info))
 		return 0;
 
+	/*
+	 * No allocations can be done from remapped block groups, so they have
+	 * no entries in the free-space tree.
+	 */
+	if (cache->flags & BTRFS_BLOCK_GROUP_REMAPPED)
+		return 0;
+
 	caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_NOFS);
 	if (!caching_ctl)
 		return -ENOMEM;
@@ -1247,10 +1254,16 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 	 * deletes the block group item from the extent tree, allowing for
 	 * another task to attempt to create another block group with the same
 	 * item key (and failing with -EEXIST and a transaction abort).
+	 *
+	 * If the REMAPPED flag has been set the block group's free space
+	 * has already been removed, so we can skip the call to
+	 * btrfs_remove_block_group_free_space().
 	 */
-	ret = btrfs_remove_block_group_free_space(trans, block_group);
-	if (ret)
-		goto out;
+	if (!(block_group->flags & BTRFS_BLOCK_GROUP_REMAPPED)) {
+		ret = btrfs_remove_block_group_free_space(trans, block_group);
+		if (ret)
+			goto out;
+	}
 
 	ret = remove_block_group_item(trans, path, block_group);
 	if (ret < 0)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 6ccb492eae8e..05ce6b5a898f 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2756,6 +2756,9 @@ int btrfs_add_free_space(struct btrfs_block_group *block_group,
 {
 	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 
+	if (block_group->flags & BTRFS_BLOCK_GROUP_REMAPPED)
+		return 0;
+
 	if (btrfs_is_zoned(block_group->fs_info))
 		return __btrfs_add_free_space_zoned(block_group, bytenr, size,
 						    true);
-- 
2.51.0