| From c9c9762d4d44dcb1b2ba90cfb4122dc11ceebf31 Mon Sep 17 00:00:00 2001 |
| From: Long Li <longli@microsoft.com> |
| Date: Mon, 7 Jun 2021 12:34:05 -0700 |
| Subject: block: return the correct bvec when checking for gaps |
| |
| From: Long Li <longli@microsoft.com> |
| |
| commit c9c9762d4d44dcb1b2ba90cfb4122dc11ceebf31 upstream. |
| |
| After commit 07173c3ec276 ("block: enable multipage bvecs"), a bvec can |
| have multiple pages. But bio_will_gap() still assumes one page bvec while |
| checking for merging. If the pages in the bvec go across the |
| seg_boundary_mask, this check for merging can potentially succeed if only |
| the 1st page is tested, and can fail if all the pages are tested. |
| |
| Later, when SCSI builds the SG list the same check for merging is done in |
| __blk_segment_map_sg_merge() with all the pages in the bvec tested. This |
| time the check may fail if the pages in bvec go across the |
| seg_boundary_mask (but tested okay in bio_will_gap() earlier, so those |
| BIOs were merged). If this check fails, we end up with a broken SG list |
| for drivers assuming the SG list not having offsets in intermediate pages. |
| This results in incorrect pages written to the disk. |
| |
| Fix this by returning the multi-page bvec when testing gaps for merging. |
| |
| Cc: Jens Axboe <axboe@kernel.dk> |
| Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> |
| Cc: Pavel Begunkov <asml.silence@gmail.com> |
| Cc: Ming Lei <ming.lei@redhat.com> |
| Cc: Tejun Heo <tj@kernel.org> |
| Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> |
| Cc: Jeffle Xu <jefflexu@linux.alibaba.com> |
| Cc: linux-kernel@vger.kernel.org |
| Cc: stable@vger.kernel.org |
| Fixes: 07173c3ec276 ("block: enable multipage bvecs") |
| Signed-off-by: Long Li <longli@microsoft.com> |
| Reviewed-by: Ming Lei <ming.lei@redhat.com> |
| Reviewed-by: Christoph Hellwig <hch@lst.de> |
| Link: https://lore.kernel.org/r/1623094445-22332-1-git-send-email-longli@linuxonhyperv.com |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/linux/bio.h | 12 ++++-------- |
| 1 file changed, 4 insertions(+), 8 deletions(-) |
| |
| --- a/include/linux/bio.h |
| +++ b/include/linux/bio.h |
| @@ -38,9 +38,6 @@ |
| #define bio_offset(bio) bio_iter_offset((bio), (bio)->bi_iter) |
| #define bio_iovec(bio) bio_iter_iovec((bio), (bio)->bi_iter) |
| |
| -#define bio_multiple_segments(bio) \ |
| - ((bio)->bi_iter.bi_size != bio_iovec(bio).bv_len) |
| - |
| #define bvec_iter_sectors(iter) ((iter).bi_size >> 9) |
| #define bvec_iter_end_sector(iter) ((iter).bi_sector + bvec_iter_sectors((iter))) |
| |
| @@ -252,7 +249,7 @@ static inline void bio_clear_flag(struct |
| |
| static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv) |
| { |
| - *bv = bio_iovec(bio); |
| + *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); |
| } |
| |
| static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) |
| @@ -260,10 +257,9 @@ static inline void bio_get_last_bvec(str |
| struct bvec_iter iter = bio->bi_iter; |
| int idx; |
| |
| - if (unlikely(!bio_multiple_segments(bio))) { |
| - *bv = bio_iovec(bio); |
| - return; |
| - } |
| + bio_get_first_bvec(bio, bv); |
| + if (bv->bv_len == bio->bi_iter.bi_size) |
| + return; /* this bio only has a single bvec */ |
| |
| bio_advance_iter(bio, &iter, iter.bi_size); |
| |