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authorMartin Wilck <mwilck@suse.com>2018-07-25 23:15:07 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-08-03 07:50:42 +0200
commit2258351cf0865b6367a5b2b3843ec39a146bb0f8 (patch)
treee03d5c1162176c99d18af0e9b05eeb0c44e537a6
parent2488689fe4684756269a961117bf348ef458d58c (diff)
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 <hare@suse.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin Wilck <mwilck@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--block/bio.c18
1 files 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;