On 22.05.2018 11:43, Qu Wenruo wrote:
> Introduce a small helper, btrfs_mark_bg_unused(), to accquire needed
> locks and add a block group to unused_bgs list.
>
> No functional modification, and only 3 callers are involved.>
> Signed-off-by: Qu Wenruo <w...@suse.com>
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
> ---
> This patch should provide the basis for later block group auto-removal
> to get more info (mostly transid) to determine should one block group
> being removed in current trans.
>
> changelog:
> v2:
> Add ASSERT() for btrfs_read_block_groups(), as in that call site a
> block group should not be added to other list (new_bgs or
> deleted_bgs).
> Rename the function to btrfs_mark_bg_unused().
> Both suggested by Nikolay.
> ---
> fs/btrfs/ctree.h | 1 +
> fs/btrfs/extent-tree.c | 36 +++++++++++++++++-------------------
> fs/btrfs/scrub.c | 9 +--------
> 3 files changed, 19 insertions(+), 27 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index bbb358143ded..4a34bc443fe4 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -2827,6 +2827,7 @@ void check_system_chunk(struct btrfs_trans_handle
> *trans,
> struct btrfs_fs_info *fs_info, const u64 type);
> u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
> u64 start, u64 end);
> +void btrfs_mark_bg_unused(struct btrfs_block_group_cache *bg);
>
> /* ctree.c */
> int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index ccf2690f7ca1..33f046103073 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -6312,16 +6312,8 @@ static int update_block_group(struct
> btrfs_trans_handle *trans,
> * dirty list to avoid races between cleaner kthread and space
> * cache writeout.
> */
> - if (!alloc && old_val == 0) {
> - spin_lock(&info->unused_bgs_lock);
> - if (list_empty(&cache->bg_list)) {
> - btrfs_get_block_group(cache);
> - trace_btrfs_add_unused_block_group(cache);
> - list_add_tail(&cache->bg_list,
> - &info->unused_bgs);
> - }
> - spin_unlock(&info->unused_bgs_lock);
> - }
> + if (!alloc && old_val == 0)
> + btrfs_mark_bg_unused(cache);
>
> btrfs_put_block_group(cache);
> total -= num_bytes;
> @@ -10144,15 +10136,8 @@ int btrfs_read_block_groups(struct btrfs_fs_info
> *info)
> if (btrfs_chunk_readonly(info, cache->key.objectid)) {
> inc_block_group_ro(cache, 1);
> } else if (btrfs_block_group_used(&cache->item) == 0) {
> - spin_lock(&info->unused_bgs_lock);
> - /* Should always be true but just in case. */
> - if (list_empty(&cache->bg_list)) {
> - btrfs_get_block_group(cache);
> - trace_btrfs_add_unused_block_group(cache);
> - list_add_tail(&cache->bg_list,
> - &info->unused_bgs);
> - }
> - spin_unlock(&info->unused_bgs_lock);
> + ASSERT(list_empty(&cache->bg_list));
> + btrfs_mark_bg_unused(cache);
> }
> }
>
> @@ -11071,3 +11056,16 @@ void btrfs_wait_for_snapshot_creation(struct
> btrfs_root *root)
> !atomic_read(&root->will_be_snapshotted));
> }
> }
> +
> +void btrfs_mark_bg_unused(struct btrfs_block_group_cache *bg)
> +{
> + struct btrfs_fs_info *fs_info = bg->fs_info;
> +
> + spin_lock(&fs_info->unused_bgs_lock);
> + if (list_empty(&bg->bg_list)) {
> + btrfs_get_block_group(bg);
> + trace_btrfs_add_unused_block_group(bg);
> + list_add_tail(&bg->bg_list, &fs_info->unused_bgs);
> + }
> + spin_unlock(&fs_info->unused_bgs_lock);
> +}
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index a59005862010..40086b47a65f 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -3981,14 +3981,7 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
> if (!cache->removed && !cache->ro && cache->reserved == 0 &&
> btrfs_block_group_used(&cache->item) == 0) {
> spin_unlock(&cache->lock);
> - spin_lock(&fs_info->unused_bgs_lock);
> - if (list_empty(&cache->bg_list)) {
> - btrfs_get_block_group(cache);
> - trace_btrfs_add_unused_block_group(cache);
> - list_add_tail(&cache->bg_list,
> - &fs_info->unused_bgs);
> - }
> - spin_unlock(&fs_info->unused_bgs_lock);
> + btrfs_mark_bg_unused(cache);
> } else {
> spin_unlock(&cache->lock);
> }
>
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