* [PATCH AUTOSEL 5.1 77/95] block: fix page leak when merging to same page
[not found] <20190627003021.19867-1-sashal@kernel.org>
@ 2019-06-27 0:30 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2019-06-27 0:30 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Christoph Hellwig, David Gibson, Ming Lei, Jens Axboe,
Sasha Levin, linux-block
From: Christoph Hellwig <hch@lst.de>
[ Upstream commit 4569180495600ac59f5cd27f67242a6cb51254f3 ]
When multiple iovecs reference the same page, each get_user_page call
will add a reference to the page. But once we've created the bio that
information gets lost and only a single reference will be dropped after
I/O completion. Use the same_page information returned from
__bio_try_merge_page to drop additional references to pages that were
already present in the bio.
Based on a patch from Ming Lei.
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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bio.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index a3c80a6c1fe5..80a25c245109 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -884,6 +884,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
unsigned short entries_left = bio->bi_max_vecs - bio->bi_vcnt;
struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
struct page **pages = (struct page **)bv;
+ bool same_page = false;
ssize_t size, left;
unsigned len, i;
size_t offset;
@@ -904,8 +905,15 @@ 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, &same_page)) {
+ if (same_page)
+ put_page(page);
+ } else {
+ if (WARN_ON_ONCE(bio_full(bio)))
+ return -EINVAL;
+ __bio_add_page(bio, page, len, offset);
+ }
offset = 0;
}
--
2.20.1
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2019-06-27 0:30 ` [PATCH AUTOSEL 5.1 77/95] block: fix page leak when merging to same page Sasha Levin
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