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| author | Boris Burkov <boris@bur.io> | 2024-06-07 22:50:14 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-06-13 21:43:45 +0300 |
| commit | 4eb4e85c4f818491efc67e9373aa16b123c3f522 (patch) | |
| tree | dd2d04a3cadfbc2fd52d050e8b473d4c8ddddbaf | |
| parent | f3a5367c679d31473d3fbb391675055b4792c309 (diff) | |
| download | linux-4eb4e85c4f818491efc67e9373aa16b123c3f522.tar.xz | |
btrfs: retry block group reclaim without infinite loop
If inc_block_group_ro systematically fails (e.g. due to ETXTBUSY from
swap) or btrfs_relocate_chunk systematically fails (from lack of
space), then this worker becomes an infinite loop.
At the very least, this strands the cleaner thread, but can also result
in hung tasks/RCU stalls on PREEMPT_NONE kernels and if the
reclaim_bgs_lock mutex is not contended.
I believe the best long term fix is to manage reclaim via work queue,
where we queue up a relocation on the triggering condition and re-queue
on failure. In the meantime, this is an easy fix to apply to avoid the
immediate pain.
Fixes: 7e2718099438 ("btrfs: reinsert BGs failed to reclaim")
CC: stable@vger.kernel.org # 6.6+
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/block-group.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index 1e09aeea69c2..1a66be33bb04 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1785,6 +1785,7 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) container_of(work, struct btrfs_fs_info, reclaim_bgs_work); struct btrfs_block_group *bg; struct btrfs_space_info *space_info; + LIST_HEAD(retry_list); if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags)) return; @@ -1921,8 +1922,11 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) } next: - if (ret) - btrfs_mark_bg_to_reclaim(bg); + if (ret) { + /* Refcount held by the reclaim_bgs list after splice. */ + btrfs_get_block_group(bg); + list_add_tail(&bg->bg_list, &retry_list); + } btrfs_put_block_group(bg); mutex_unlock(&fs_info->reclaim_bgs_lock); @@ -1942,6 +1946,9 @@ next: spin_unlock(&fs_info->unused_bgs_lock); mutex_unlock(&fs_info->reclaim_bgs_lock); end: + spin_lock(&fs_info->unused_bgs_lock); + list_splice_tail(&retry_list, &fs_info->reclaim_bgs); + spin_unlock(&fs_info->unused_bgs_lock); btrfs_exclop_finish(fs_info); sb_end_write(fs_info->sb); } |