On Sun, Mar 24, 2024 at 04:25:04PM -0700, Christoph Hellwig wrote:
> On Sun, Mar 24, 2024 at 09:37:02PM +0800, Ming Lei wrote:
> > +static bool bio_check_alignment(struct bio *bio, struct request_queue *q)
> > +{
> > + unsigned int bs = q->limits.logical_block_size;
> > +
> > + if (bio->bi_iter.bi_size & (bs - 1))
> > + return false;
> > +
> > + if (bio->bi_iter.bi_sector & ((bs >> SECTOR_SHIFT) - 1))
> > + return false;
> > +
> > + return true;
> > +}
>
>
> This should still use bdev_logic_block_size. And maybe it's just me,
> but I think dropping thelines after the false returns would actually
> make it more readle.
OK, will remove the blank line.
>
> > diff --git a/block/fops.c b/block/fops.c
> > index 679d9b752fe8..75595c728190 100644
> > --- a/block/fops.c
> > +++ b/block/fops.c
> > @@ -37,8 +37,7 @@ static blk_opf_t dio_bio_write_op(struct kiocb *iocb)
> > static bool blkdev_dio_unaligned(struct block_device *bdev, loff_t pos,
> > struct iov_iter *iter)
> > {
> > - return pos & (bdev_logical_block_size(bdev) - 1) ||
> > - !bdev_iter_is_aligned(bdev, iter);
> > + return !bdev_iter_is_aligned(bdev, iter);
>
> If you drop this:
>
> - we now actually go all the way down to building and submiting a
> bio for a trivial bounds check.
> - your get a trivial to trigger WARN_ON.
>
> I'd strongly advise against dropping this check.
OK.
Also only q->limits.logical_block_size is fetched for small BS IO
fast path, I think log(lbs) can be cached in request_queue for avoiding the
extra fetch of q.limits. Especially, it could be easier to do so
with your recent queue limit atomic update changes.
Thanks,
Ming
