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Subject[PATCH 5.8 052/177] block: Set same_page to false in __bio_try_merge_page if ret is false
Date
From: Ritesh Harjani <riteshh@linux.ibm.com>

[ Upstream commit 2cd896a5e86fc326bda8614b96c0401dcc145868 ]

If we hit the UINT_MAX limit of bio->bi_iter.bi_size and so we are anyway
not merging this page in this bio, then it make sense to make same_page
also as false before returning.

Without this patch, we hit below WARNING in iomap.
This mostly happens with very large memory system and / or after tweaking
vm dirty threshold params to delay writeback of dirty data.

WARNING: CPU: 18 PID: 5130 at fs/iomap/buffered-io.c:74 iomap_page_release+0x120/0x150
CPU: 18 PID: 5130 Comm: fio Kdump: loaded Tainted: G W 5.8.0-rc3 #6
Call Trace:
__remove_mapping+0x154/0x320 (unreliable)
iomap_releasepage+0x80/0x180
try_to_release_page+0x94/0xe0
invalidate_inode_page+0xc8/0x110
invalidate_mapping_pages+0x1dc/0x540
generic_fadvise+0x3c8/0x450
xfs_file_fadvise+0x2c/0xe0 [xfs]
vfs_fadvise+0x3c/0x60
ksys_fadvise64_64+0x68/0xe0
sys_fadvise64+0x28/0x40
system_call_exception+0xf8/0x1c0
system_call_common+0xf0/0x278

Fixes: cc90bc68422 ("block: fix "check bi_size overflow before merge"")
Reported-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bio.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index b1883adc8f154..eac129f21d2df 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -877,8 +877,10 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];

if (page_is_mergeable(bv, page, len, off, same_page)) {
- if (bio->bi_iter.bi_size > UINT_MAX - len)
+ if (bio->bi_iter.bi_size > UINT_MAX - len) {
+ *same_page = false;
return false;
+ }
bv->bv_len += len;
bio->bi_iter.bi_size += len;
return true;
--
2.25.1


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