Commit 2ca0ec77 authored by Johannes Thumshirn's avatar Johannes Thumshirn Committed by David Sterba
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btrfs: zoned: use greedy gc for auto reclaim 



Currently auto reclaim of unusable zones reclaims the block-groups in
the order they have been added to the reclaim list.

Change this to a greedy algorithm by sorting the list so we have the
block-groups with the least amount of valid bytes reclaimed first.

Note: we can't splice the block groups from reclaim_bgs to let the sort
happen outside of the lock. The block groups can be still in use by
other parts eg. via bg_list and we must hold unused_bgs_lock while
processing them.

Signed-off-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
[ write note and comment why we can't splice the list ]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 813ebc16

fs/btrfs/block-group.c

+22 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <linux/list_sort.h>

#include "misc.h"

#include "ctree.h"

#include "block-group.h"
@@ -1486,6 +1487,21 @@ void btrfs_mark_bg_unused(struct btrfs_block_group *bg) 
	spin_unlock(&fs_info->unused_bgs_lock);

}



/*

 * We want block groups with a low number of used bytes to be in the beginning

 * of the list, so they will get reclaimed first.

 */

static int reclaim_bgs_cmp(void *unused, const struct list_head *a,

			   const struct list_head *b)

{

	const struct btrfs_block_group *bg1, *bg2;



	bg1 = list_entry(a, struct btrfs_block_group, bg_list);

	bg2 = list_entry(b, struct btrfs_block_group, bg_list);



	return bg1->used > bg2->used;

}



void btrfs_reclaim_bgs_work(struct work_struct *work)

{

	struct btrfs_fs_info *fs_info =
@@ -1510,6 +1526,12 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) 
	}



	spin_lock(&fs_info->unused_bgs_lock);

	/*

	 * Sort happens under lock because we can't simply splice it and sort.

	 * The block groups might still be in use and reachable via bg_list,

	 * and their presence in the reclaim_bgs list must be preserved.

	 */

	list_sort(NULL, &fs_info->reclaim_bgs, reclaim_bgs_cmp);

	while (!list_empty(&fs_info->reclaim_bgs)) {

		u64 zone_unusable;

		int ret = 0;