btrfs: zoned: reset zones of relocated block groups

When relocating a block group the freed up space is not discarded in one
big block, but each extent is discarded on its own with -odisard=sync.

For a zoned filesystem we need to discard the whole block group at once,
so btrfs_discard_extent() will translate the discard into a
REQ_OP_ZONE_RESET operation, which then resets the device's zone.
Failure to reset the zone is not fatal error.

Discussion about the approach and regarding transaction blocking:
https://lore.kernel.org/linux-btrfs/CAL3q7H4SjS_d5rBepfTMhU8Th3bJzdmyYd0g4Z60yUgC_rC_ZA@mail.gmail.com/

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 517b404..42377af 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3103,6 +3103,7 @@ static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
        struct btrfs_root *root = fs_info->chunk_root;
        struct btrfs_trans_handle *trans;
        struct btrfs_block_group *block_group;
+       u64 length;
        int ret;
 
        /*
@@ -3130,8 +3131,23 @@ static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
        if (!block_group)
                return -ENOENT;
        btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
+       length = block_group->length;
        btrfs_put_block_group(block_group);
 
+       /*
+        * On a zoned file system, discard the whole block group, this will
+        * trigger a REQ_OP_ZONE_RESET operation on the device zone. If
+        * resetting the zone fails, don't treat it as a fatal problem from the
+        * filesystem's point of view.
+        */
+       if (btrfs_is_zoned(fs_info)) {
+               ret = btrfs_discard_extent(fs_info, chunk_offset, length, NULL);
+               if (ret)
+                       btrfs_info(fs_info,
+                               "failed to reset zone %llu after relocation",
+                               chunk_offset);
+       }
+
        trans = btrfs_start_trans_remove_block_group(root->fs_info,
                                                     chunk_offset);
        if (IS_ERR(trans)) {