Hello Pavel,
Recently I tried out for-next branch and observed that simple dd command to
zonefs files causes an I/O error.
$ sudo dd if=/dev/zero of=/mnt/seq/0 bs=4096 count=1 oflag=direct
dd: error writing '/mnt/seq/0': Input/output error
1+0 records in
0+0 records out
0 bytes copied, 0.00409641 s, 0.0 kB/s
At that time, kernel reported warnings.
[90713.298721][ T2735] zonefs (nvme0n1) WARNING: inode 1: invalid size 0 (should be 4096)
[90713.299761][ T2735] zonefs (nvme0n1) WARNING: remounting filesystem read-only
I bisected and found that this patch triggers the error and warnings. I think
one liner change is needed in this patch. Please find it below, in line.
On Oct 19, 2021 / 22:24, Pavel Begunkov wrote:
> First, get rid of an extra branch and chain error checks. Also reshuffle
> it with bio_advance(), so it goes closer to the final check, with that
> the compiler loads rq->rq_flags only once, and also doesn't reload
> bio->bi_iter.bi_size if bio_advance() didn't actually advanced the iter.
>
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> block/blk-mq.c | 16 +++++++---------
> 1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 3481a8712234..bab1fccda6ca 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -617,25 +617,23 @@ void blk_mq_free_plug_rqs(struct blk_plug *plug)
> static void req_bio_endio(struct request *rq, struct bio *bio,
> unsigned int nbytes, blk_status_t error)
> {
> - if (error)
> + if (unlikely(error)) {
> bio->bi_status = error;
> -
> - if (unlikely(rq->rq_flags & RQF_QUIET))
> - bio_set_flag(bio, BIO_QUIET);
> -
> - bio_advance(bio, nbytes);
> -
> - if (req_op(rq) == REQ_OP_ZONE_APPEND && error == BLK_STS_OK) {
> + } else if (req_op(rq) == REQ_OP_ZONE_APPEND) {
> /*
> * Partial zone append completions cannot be supported as the
> * BIO fragments may end up not being written sequentially.
> */
> - if (bio->bi_iter.bi_size)
> + if (bio->bi_iter.bi_size == nbytes)
I think the line above should be,
if (bio->bi_iter.bi_size != nbytes)
Before applying the patch, the if statement checked "bi_size is not zero".
After applying the patch, bio_advance(bio, nbytes) moved after this check.
Then bi_size is not decremented by nbytes and the check should be "bi_size is
not nbytes". With this modification, the I/O error and the warnings go away.
> bio->bi_status = BLK_STS_IOERR;
> else
> bio->bi_iter.bi_sector = rq->__sector;
> }
>
> + bio_advance(bio, nbytes);
> +
> + if (unlikely(rq->rq_flags & RQF_QUIET))
> + bio_set_flag(bio, BIO_QUIET);
> /* don't actually finish bio if it's part of flush sequence */
> if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
> bio_endio(bio);
> --
> 2.33.1
>
--
Best Regards,
Shin'ichiro Kawasaki
