From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Martin Wilck To: Jens Axboe , Ming Lei , Jan Kara Cc: Hannes Reinecke , Johannes Thumshirn , Kent Overstreet , Christoph Hellwig , linux-block@vger.kernel.org, Martin Wilck Subject: [PATCH 1/2] block: bio_iov_iter_get_pages: fix size of last iovec Date: Thu, 19 Jul 2018 11:39:17 +0200 Message-Id: <20180719093918.28876-2-mwilck@suse.com> In-Reply-To: <20180719093918.28876-1-mwilck@suse.com> References: <20180718075440.GA15254@ming.t460p> <20180719093918.28876-1-mwilck@suse.com> List-ID: 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. Fixes: 2cefe4dbaadf ("block: add bio_iov_iter_get_pages()") Signed-off-by: Martin Wilck --- block/bio.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/block/bio.c b/block/bio.c index 67eff5e..0964328 100644 --- a/block/bio.c +++ b/block/bio.c @@ -912,16 +912,16 @@ 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 idx, nr_pages = bio->bi_max_vecs - bio->bi_vcnt; 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 @@ -934,17 +934,15 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) 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; -- 2.17.1