[PATCH 4.14 215/246] block: bio_iov_iter_get_pages: fix size of last iovec
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2018-08-01 17:22:40
Also in:
lkml
4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Wilck <redacted>
commit b403ea2404889e1227812fa9657667a1deb9c694 upstream.
If the last page of the bio is not "full", the length of the last
vector slot needs to be corrected. This slot has the index
(bio->bi_vcnt - 1), but only in bio->bi_io_vec. In the "bv" helper
array, which is shifted by the value of bio->bi_vcnt at function
invocation, the correct index is (nr_pages - 1).
v2: improved readability following suggestions from Ming Lei.
v3: followed a formatting suggestion from Christoph Hellwig.
Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()")
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Ming Lei <redacted>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin Wilck <redacted>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
block/bio.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
--- a/block/bio.c
+++ b/block/bio.c@@ -881,16 +881,16 @@ EXPORT_SYMBOL(bio_add_page); */ 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 nr_pages = bio->bi_max_vecs - bio->bi_vcnt, idx; struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt; struct page **pages = (struct page **)bv; - size_t offset, diff; + size_t offset; ssize_t size; size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset); if (unlikely(size <= 0)) return size ? size : -EFAULT; - nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; + idx = nr_pages = (size + offset + PAGE_SIZE - 1) / PAGE_SIZE; /* * Deep magic below: We need to walk the pinned pages backwards
@@ -903,17 +903,15 @@ int bio_iov_iter_get_pages(struct bio *b bio->bi_iter.bi_size += size; bio->bi_vcnt += nr_pages; - diff = (nr_pages * PAGE_SIZE - offset) - size; - while (nr_pages--) { - bv[nr_pages].bv_page = pages[nr_pages]; - bv[nr_pages].bv_len = PAGE_SIZE; - bv[nr_pages].bv_offset = 0; + while (idx--) { + bv[idx].bv_page = pages[idx]; + bv[idx].bv_len = PAGE_SIZE; + bv[idx].bv_offset = 0; } bv[0].bv_offset += offset; bv[0].bv_len -= offset; - if (diff) - bv[bio->bi_vcnt - 1].bv_len -= diff; + bv[nr_pages - 1].bv_len -= nr_pages * PAGE_SIZE - offset - size; iov_iter_advance(iter, size); return 0;