Commit 5cb0724e authored by Dennis Zhou's avatar Dennis Zhou Committed by David Sterba
Browse files

btrfs: only keep track of data extents for async discard 



As mentioned earlier, discarding data can be done either by issuing an
explicit discard or implicitly by reusing the LBA. Metadata block_groups
see much more frequent reuse due to well it being metadata. So instead
of explicitly discarding metadata block_groups, just leave them be and
let the latter implicit discarding be done for them.

For mixed block_groups, block_groups which contain both metadata and
data, we let them be as higher fragmentation is expected.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarDennis Zhou <dennis@kernel.org>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 7fe6d45e

fs/btrfs/block-group.h

+11 −0
Original line number Diff line number Diff line
@@ -182,6 +182,17 @@ static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group) 
	return (block_group->start + block_group->length);

}



static inline bool btrfs_is_block_group_data_only(

					struct btrfs_block_group *block_group)

{

	/*

	 * In mixed mode the fragmentation is expected to be high, lowering the

	 * efficiency, so only proper data block groups are considered.

	 */

	return (block_group->flags & BTRFS_BLOCK_GROUP_DATA) &&

	       !(block_group->flags & BTRFS_BLOCK_GROUP_METADATA);

}



#ifdef CONFIG_BTRFS_DEBUG

static inline int btrfs_should_fragment_free_space(

		struct btrfs_block_group *block_group)

fs/btrfs/discard.c

+10 −2
Original line number Diff line number Diff line
@@ -57,6 +57,9 @@ static void __add_to_discard_list(struct btrfs_discard_ctl *discard_ctl, 
static void add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,

				struct btrfs_block_group *block_group)

{

	if (!btrfs_is_block_group_data_only(block_group))

		return;



	spin_lock(&discard_ctl->lock);

	__add_to_discard_list(discard_ctl, block_group);

	spin_unlock(&discard_ctl->lock);
@@ -169,7 +172,10 @@ static struct btrfs_block_group *peek_discard_list( 
	if (block_group && now > block_group->discard_eligible_time) {

		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&

		    block_group->used != 0) {

			if (btrfs_is_block_group_data_only(block_group))

				__add_to_discard_list(discard_ctl, block_group);

			else

				list_del_init(&block_group->discard_list);

			goto again;

		}

		if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
@@ -507,7 +513,9 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group, 
	s32 extents_delta;

	s64 bytes_delta;



	if (!block_group || !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))

	if (!block_group ||

	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||

	    !btrfs_is_block_group_data_only(block_group))

		return;



	discard_ctl = &block_group->fs_info->discard_ctl;