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>

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 5f75cf0e14b9510346b9ae6444a41ba61e76f5b5..e3e141258a22b50dba58a8ac9c88ffdca6d593b7 100644 (file)
--- 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;
        }