[PATCH Next] gfs2: update end and prev bio for chain bio

The bios are created and initialized using gfs2_log_alloc_bio() in
gfs2_find_jhead(), which sets bi_end_io and bi_private. When the I/O
request is too large and needs to be split into multiple bios and
submitted as a chain, the bug reported by syzbot [1] is triggered.

When we need to submit multiple bios in a chain, we need to pass the
bi_end_io and bi_private of the previous bio to the end bio to ensure
that the multiple bios are correctly assembled into a submission chain.

[1]
kernel BUG at block/bio.c:342!
Call Trace:
 gfs2_chain_bio fs/gfs2/lops.c:487 [inline]
 gfs2_find_jhead+0x627/0xe40 fs/gfs2/lops.c:549
 gfs2_recover_func+0x5f5/0x1c90 fs/gfs2/recovery.c:459

Fixes: 8a157e0a0aa5 ("gfs2: Fix use of bio_chain")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=f6539d4ce3f775aee0cc
Signed-off-by: Edward Adam Davis <[email protected]>
---
 fs/gfs2/lops.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 97ebe457c00a..2de334034c74 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -484,6 +484,10 @@ static struct bio *gfs2_chain_bio(struct bio *prev, unsigned int nr_iovecs)
 	new = bio_alloc(prev->bi_bdev, nr_iovecs, prev->bi_opf, GFP_NOIO);
 	bio_clone_blkg_association(new, prev);
 	new->bi_iter.bi_sector = bio_end_sector(prev);
+	new->bi_end_io = prev->bi_end_io;
+	new->bi_private = prev->bi_private;
+	prev->bi_end_io = NULL;
+	prev->bi_private = NULL;
 	bio_chain(prev, new);
 	submit_bio(prev);
 	return new;
-- 
2.43.0