btrfs: zoned: always set data_relocation_bg

When searching for a data relocation block-group on mount,
btrfs_zoned_reserve_data_reloc_bg() is looking for the first empty DATA
block-group. But it first checks if the block-group is empty and if yes
continues the search, and then checks if it is the first DATA block-group.

There is actually no point in looking for the second empty DATA block
group as new DATA allocations will just allocate a new chunk for it. Pick
the first DATA block-group without any allocations done and set it as
relocation block-group.

At first, the commit 694ce5e143d6 ("btrfs: zoned: reserve data_reloc
block group on mount") introduced the functionality. At that time, we
took second unused (used == 0) block group, as the first one might be a
block group used for normal data.  Later, commit daa0fde32235 ("btrfs:
zoned: fix data relocation block group reservation") switched to look
for an empty block group (alloc_offset == 0). At this point, there is no
reason taking the second one anymore. So, this commit is fixing an issue
in commit daa0fde32235.

Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 10 deletions

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 5f75cf0e14b9..e3e141258a22 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2765,7 +2765,6 @@ void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
 	struct btrfs_block_group *bg;
 	struct list_head *bg_list;
 	u64 alloc_flags;
-	bool first = true;
 	bool did_chunk_alloc = false;
 	int index;
 	int ret;
@@ -2782,17 +2781,12 @@ void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
 	alloc_flags = btrfs_get_alloc_profile(fs_info, space_info->flags);
 	index = btrfs_bg_flags_to_raid_index(alloc_flags);
 
-	/* Scan the data space_info to find empty block groups. Take the second one. */
 again:
 	bg_list = &space_info->block_groups[index];
 	list_for_each_entry(bg, bg_list, list) {
-		if (bg->alloc_offset != 0)
-			continue;
 
-		if (first) {
-			first = false;
+		if (bg->alloc_offset != 0)
 			continue;
-		}
 
 		if (space_info == data_sinfo) {
 			/* Migrate the block group to the data relocation space_info. */
@@ -2805,8 +2799,6 @@ again:
 
 			down_write(&space_info->groups_sem);
 			list_del_init(&bg->list);
-			/* We can assume this as we choose the second empty one. */
-			ASSERT(!list_empty(&space_info->block_groups[index]));
 			up_write(&space_info->groups_sem);
 
 			spin_lock(&space_info->lock);
@@ -2851,7 +2843,6 @@ again:
 		 * We allocated a new block group in the data relocation space_info. We
 		 * can take that one.
 		 */
-		first = false;
 		did_chunk_alloc = true;
 		goto again;
 	}