From 2258351cf0865b6367a5b2b3843ec39a146bb0f8 Mon Sep 17 00:00:00 2001 From: Martin Wilck Date: Wed, 25 Jul 2018 23:15:07 +0200 Subject: [PATCH] block: bio_iov_iter_get_pages: fix size of last iovec 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 Reviewed-by: Ming Lei Reviewed-by: Jan Kara Reviewed-by: Christoph Hellwig Signed-off-by: Martin Wilck Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/bio.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/block/bio.c b/block/bio.c index 90f19d7df66c..e5df69918d1a 100644 --- 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 *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;