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block: fix aligning of bounced dio read bios

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bio_iov_iter_align_down expects the "normal" biovec layout from vector 0,
while bio_iov_iter_bounce_read abuses vector 0 for a bounce buffer
allocation.  Pass an explicit bvec to bio_iov_iter_align_down to deal
with this case to avoid a double unpin.

Additionally we need to free the folio if no bio_vec could be added,
and adjust the size of the first bio_vec that contains the bounce buffer
when the I/O size is aligned down.

Fixes: e7b8b3c5b2 ("block: align down bounces bios")
Reported-by: 0wnerD1ed <l7z@0b1t.tech>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: 0wnerD1ed <l7z@0b1t.tech>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Link: https://patch.msgid.link/20260716091306.316625-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2026-07-16 11:12:46 +02:00 committed by Jens Axboe
parent 4f221efff9
commit df308a1458
1 changed files with 28 additions and 23 deletions
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51
block/bio.c
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@ -1199,7 +1199,7 @@ void bio_iov_bvec_set(struct bio *bio, const struct iov_iter *iter)
* for the next iteration.
*/
static int bio_iov_iter_align_down(struct bio *bio, struct iov_iter *iter,
unsigned len_align_mask)
struct bio_vec *bv, unsigned len_align_mask)
{
size_t nbytes = bio->bi_iter.bi_size & len_align_mask;
@ -1208,23 +1208,16 @@ static int bio_iov_iter_align_down(struct bio *bio, struct iov_iter *iter,
iov_iter_revert(iter, nbytes);
bio->bi_iter.bi_size -= nbytes;
do {
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
if (nbytes < bv->bv_len) {
bv->bv_len -= nbytes;
break;
}
while (nbytes >= bv->bv_len) {
if (bio_flagged(bio, BIO_PAGE_PINNED))
unpin_user_page(bv->bv_page);
bio->bi_vcnt--;
if (!--bio->bi_vcnt)
return -EFAULT;
nbytes -= bv->bv_len;
} while (nbytes);
if (!bio->bi_vcnt)
return -EFAULT;
bv--;
}
bv->bv_len -= nbytes;
return 0;
}
@ -1284,7 +1277,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter,
if (is_pci_p2pdma_page(bio->bi_io_vec->bv_page))
bio->bi_opf |= REQ_NOMERGE;
return bio_iov_iter_align_down(bio, iter, len_align_mask);
return bio_iov_iter_align_down(bio, iter,
&bio->bi_io_vec[bio->bi_vcnt - 1], len_align_mask);
}
static struct folio *folio_alloc_greedy(gfp_t gfp, size_t *size,
@ -1369,7 +1363,8 @@ static int bio_iov_iter_bounce_write(struct bio *bio, struct iov_iter *iter,
if (!bio->bi_iter.bi_size)
return -ENOMEM;
return bio_iov_iter_align_down(bio, iter, minsize - 1);
return bio_iov_iter_align_down(bio, iter,
&bio->bi_io_vec[bio->bi_vcnt - 1], minsize - 1);
}
static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter,
@ -1377,21 +1372,18 @@ static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter,
{
size_t len = min3(iov_iter_count(iter), maxlen, SZ_1M);
struct folio *folio;
ssize_t ret;
folio = folio_alloc_greedy(GFP_KERNEL, &len, minsize);
if (!folio)
return -ENOMEM;
do {
ssize_t ret;
ret = iov_iter_extract_bvecs(iter, bio->bi_io_vec + 1, len,
&bio->bi_vcnt, bio->bi_max_vecs - 1, 0);
if (ret <= 0) {
if (!bio->bi_vcnt) {
folio_put(folio);
return ret;
}
if (!bio->bi_vcnt)
goto out_folio_put;
break;
}
len -= ret;
@ -1407,7 +1399,20 @@ static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter,
bvec_set_folio(&bio->bi_io_vec[0], folio, bio->bi_iter.bi_size, 0);
if (iov_iter_extract_will_pin(iter))
bio_set_flag(bio, BIO_PAGE_PINNED);
return bio_iov_iter_align_down(bio, iter, minsize - 1);
/* The first vec stores the bounce buffer, so do not subtract 1 here. */
ret = bio_iov_iter_align_down(bio, iter,
&bio->bi_io_vec[bio->bi_vcnt], minsize - 1);
if (ret)
goto out_folio_put;
/* Update the bounc buffer bv_len to the aligned down size. */
bio->bi_io_vec[0].bv_len = bio->bi_iter.bi_size;
return 0;
out_folio_put:
folio_put(folio);
return ret;
}
/**