@@ -652,6 +652,9 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
return false;
if (pfn_to_page(PFN_DOWN(vec_end_addr)) + 1 != page)
return false;
+ /* drop page ref if the page has been added and user asks to do that */
+ } else if (flags & BVEC_MERGE_PUT_SAME_PAGE) {
+ put_page(page);
}
WARN_ON_ONCE((flags & BVEC_MERGE_TO_SAME_PAGE) &&
@@ -924,8 +927,13 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
struct page *page = pages[i];
len = min_t(size_t, PAGE_SIZE - offset, left);
- if (WARN_ON_ONCE(bio_add_page(bio, page, len, offset) != len))
- return -EINVAL;
+
+ if (!__bio_try_merge_page(bio, page, len, offset,
+ BVEC_MERGE_PUT_SAME_PAGE)) {
+ if (WARN_ON_ONCE(bio_full(bio)))
+ return -EINVAL;
+ __bio_add_page(bio, page, len, offset);
+ }
offset = 0;
}
@@ -428,6 +428,14 @@ enum bvec_merge_flags {
* bvec
*/
BVEC_MERGE_TO_SAME_PAGE = BIT(0),
+
+ /*
+ * put refcount of bio's last page if the start page to add is
+ * same with bio's last page. If user gets refcount of every
+ * page added to bio before calling bio_add_page, please consider
+ * to use this flag for avoiding page leak
+ */
+ BVEC_MERGE_PUT_SAME_PAGE = BIT(1),
};
extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
Different iovec may use one same page, then 'pages' array filled by iov_iter_get_pages() may get reference of the same page several times. If some elements in 'pages' can be merged to same page in one bvec by bio_add_page(), bio_release_pages() only drops the page's reference once. This way causes page leak reported by David Gibson. This issue can be triggered since 576ed913 ("block: use bio_add_page in bio_iov_iter_get_pages"). Fixes the issue by putting the page's ref if it is merged to same page. Cc: David Gibson <david@gibson.dropbear.id.au> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: linux-xfs@vger.kernel.org Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Link: https://lkml.org/lkml/2019/4/23/64 Fixes: 576ed913 ("block: use bio_add_page in bio_iov_iter_get_pages") Reported-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/bio.c | 12 ++++++++++-- include/linux/bio.h | 8 ++++++++ 2 files changed, 18 insertions(+), 2 deletions(-)