Re: [PATCH 3/3] block: ensure direct io is a block size

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On Mon, May 16, 2022 at 12:13:10PM +0200, Damien Le Moal wrote:
> On 2022/05/13 18:13, Keith Busch wrote:
> > From: Keith Busch <kbusch@xxxxxxxxxx>
> > 
> > If the iterator has an offset, filling a bio to the max bvecs may result
> > in a size that isn't aligned to the block size. Mask off bytes for the
> > bio being constructed.
> > 
> > Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
> > ---
> >  block/bio.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/block/bio.c b/block/bio.c
> > index 4259125e16ab..b42a9e3ff068 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -1144,6 +1144,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> >  {
> >  	unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
> >  	unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
> > +	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
> >  	struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
> >  	struct page **pages = (struct page **)bv;
> >  	bool same_page = false;
> > @@ -1160,6 +1161,9 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> >  	pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
> >  
> >  	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> > +	if (size > 0)
> > +		size = size & ~(queue_logical_block_size(q) - 1);
> 
> I think that __bio_iov_append_get_pages() needs the same change. And given that
> both __bio_iov_append_get_pages() and __bio_iov_iter_get_pages() start with
> iov_iter_get_pages(), should we do that and check the size in the single caller:
> bio_iov_iter_get_pages() ?

Right, __bio_iov_append_get_pages needs this too. I'll see if we can remove much
of the duplicated code among these two functions as a prep patch.



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