Re: [block:for-3.14/core] kernel BUG at fs/bio.c:1748

From: Muthu Kumar
Date: Tue Jan 07 2014 - 15:15:52 EST

Thanks Fengguang. Final patch with added comment. BTW, fengguang
mentioned that git-am has trouble with the inline patch and "quilt
import" worked fine for him...

In btrfs_end_bio(), we increment bi_remaining if is_orig_bio. If not,
we restore the orig_bio but failed to increment bi_remaining for
orig_bio, which triggers a BUG_ON later when bio_endio is called. Fix
is to increment bi_remaining when we restore the orig bio as well.

Reported-and-Tested-by: Fengguang wu <fengguang.wu@xxxxxxxxx>
CC: Kent Overstreet <kmo@xxxxxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
CC: Chris Mason <clm@xxxxxx>
Signed-off-by: Muthukumar Ratty <muthur@xxxxxxxxx>

fs/btrfs/volumes.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 37972d5..34aba2b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5297,9 +5297,13 @@ static void btrfs_end_bio(struct bio *bio, int err)
if (!is_orig_bio) {
bio = bbio->orig_bio;
- } else {
- atomic_inc(&bio->bi_remaining);
+ /*
+ * We have original bio now. So increment bi_remaining to
+ * account for it in endio
+ */
+ atomic_inc(&bio->bi_remaining);
bio->bi_private = bbio->private;
bio->bi_end_io = bbio->end_io;
btrfs_io_bio(bio)->mirror_num = bbio->mirror_num;

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