| Message ID | 20190607131025.31996-14-naohiro.aota@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs zoned block device support | expand |
On Fri, Jun 07, 2019 at 10:10:19PM +0900, Naohiro Aota wrote: > Btrfs prioritize sync I/Os to be handled by async checksum worker earlier. > As a result, checksumming sync I/Os to larger logical extent address can > finish faster than checksumming non-sync I/Os to smaller logical extent > address. > > Since we have upper limit of number of checksum worker, it is possible that > sync I/Os to wait forever for non-starting checksum of I/Os for smaller > address. > > This situation can be reproduced by e.g. fstests btrfs/073. > > To avoid such disordering, disable sync IO prioritization for now. Note > that sync I/Os anyway must wait for I/Os to smaller address to finish. So, > actually prioritization have no benefit in HMZONED mode. > This stuff is going away once we finish the io.weight work anyway, I wouldn't worry about this. Thanks, Josef
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 56a416902ce7..6651986da470 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -838,7 +838,7 @@ blk_status_t btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, async->status = 0; - if (op_is_sync(bio->bi_opf)) + if (op_is_sync(bio->bi_opf) && !btrfs_fs_incompat(fs_info, HMZONED)) btrfs_set_work_high_priority(&async->work); btrfs_queue_work(fs_info->workers, &async->work);
Btrfs prioritize sync I/Os to be handled by async checksum worker earlier. As a result, checksumming sync I/Os to larger logical extent address can finish faster than checksumming non-sync I/Os to smaller logical extent address. Since we have upper limit of number of checksum worker, it is possible that sync I/Os to wait forever for non-starting checksum of I/Os for smaller address. This situation can be reproduced by e.g. fstests btrfs/073. To avoid such disordering, disable sync IO prioritization for now. Note that sync I/Os anyway must wait for I/Os to smaller address to finish. So, actually prioritization have no benefit in HMZONED mode. Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> --- fs/btrfs/disk-io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)