[PATCH 4.5 166/238] md: multipath: dont hardcopy bio in .make_request path

From: Greg Kroah-Hartman
Date: Sun Apr 10 2016 - 16:21:30 EST


4.5-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ming Lei <ming.lei@xxxxxxxxxxxxx>

commit fafcde3ac1a418688a734365203a12483b83907a upstream.

Inside multipath_make_request(), multipath maps the incoming
bio into low level device's bio, but it is totally wrong to
copy the bio into mapped bio via '*mapped_bio = *bio'. For
example, .__bi_remaining is kept in the copy, especially if
the incoming bio is chained to via bio splitting, so .bi_end_io
can't be called for the mapped bio at all in the completing path
in this kind of situation.

This patch fixes the issue by using clone style.

Reported-and-tested-by: Andrea Righi <righi.andrea@xxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/md/multipath.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -129,7 +129,9 @@ static void multipath_make_request(struc
}
multipath = conf->multipaths + mp_bh->path;

- mp_bh->bio = *bio;
+ bio_init(&mp_bh->bio);
+ __bio_clone_fast(&mp_bh->bio, bio);
+
mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
mp_bh->bio.bi_bdev = multipath->rdev->bdev;
mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT;