On Tue, Jan 26, 2021 at 11:25:10AM +0900, Naohiro Aota wrote: > In ZONED, btrfs uses per-FS zoned_meta_io_lock to serialize the metadata > write IOs. > > Even with these 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 can disable async metadata checksum on > ZONED. 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 performance. > > Reviewed-by: Josef Bacik <[email protected]> > Signed-off-by: Naohiro Aota <[email protected]> > --- > 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 a41bdf9312d6..5d14100ecf72 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -814,6 +814,8 @@ 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;
This check need to be after the other ones as zoned is a static per-fs status, while other others depend on either current state or system state (crypto implementation). > if (atomic_read(&bi->sync_writers)) > return 0; > if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags)) > -- > 2.27.0
