From 4eef29ef6360d9c3e4be111392e20b70e19171cc Mon Sep 17 00:00:00 2001 From: Naohiro Aota Date: Thu, 4 Feb 2021 19:22:10 +0900 Subject: [PATCH] btrfs: zoned: do not use async metadata checksum on zoned filesystems On zoned filesystems, btrfs uses per-fs zoned_meta_io_lock to serialize the metadata write IOs. Even with this serialization, write bios sent from btree_write_cache_pages can be reordered by async checksum workers as these workers are per CPU and not per zone. To preserve write bio ordering, we disable async metadata checksum on a zoned filesystem. This does not result in lower performance with HDDs as a single CPU core is fast enough to do checksum for a single zone write stream with the maximum possible bandwidth of the device. If multiple zones are being written simultaneously, HDD seek overhead lowers the achievable maximum bandwidth, resulting again in a per zone checksum serialization not affecting the performance. Reviewed-by: Josef Bacik Signed-off-by: Naohiro Aota Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/disk-io.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 458bb27e0327..6e16f556ed75 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -871,6 +871,8 @@ static blk_status_t btree_submit_bio_start(struct inode *inode, struct bio *bio, static int check_async_write(struct btrfs_fs_info *fs_info, struct btrfs_inode *bi) { + if (btrfs_is_zoned(fs_info)) + return 0; if (atomic_read(&bi->sync_writers)) return 0; if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags)) -- GitLab