提交 b403ea24 编写于 作者: M Martin Wilck 提交者: Jens Axboe

block: bio_iov_iter_get_pages: fix size of last iovec

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: 2cefe4db ("block: add bio_iov_iter_get_pages()")
Reviewed-by: NHannes Reinecke <hare@suse.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMartin Wilck <mwilck@suse.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
上级 78e18063
......@@ -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 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
......@@ -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;
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册