Patch "md: multipath: don't hardcopy bio in .make_request path" has been added to the 4.4-stable tree

Patch "md: multipath: don't hardcopy bio in .make_request path" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    md: multipath: don't hardcopy bio in .make_request path

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     md-multipath-don-t-hardcopy-bio-in-.make_request-path.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From fafcde3ac1a418688a734365203a12483b83907a Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@canonical.com>
Date: Sat, 12 Mar 2016 09:29:40 +0800
Subject: md: multipath: don't hardcopy bio in .make_request path

From: Ming Lei <ming.lei@canonical.com>

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@gmail.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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;


Patches currently in stable-queue which might be from ming.lei@canonical.com are

queue-4.4/md-multipath-don-t-hardcopy-bio-in-.make_request-path.patch