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

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Message-ID: <CAFR8ueeC_fqpN+M5YOr8AT_o3BDgr+o1ELQQJQSW7s8uDm2y5Q@mail.gmail.com>
Date:	Tue, 7 Jan 2014 12:15:39 -0800
From:	Muthu Kumar <muthu.lkml@...il.com>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	Kent Overstreet <kmo@...erainc.com>, Chris Mason <clm@...com>,
	Jens Axboe <axboe@...nel.dk>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, lkp@...ux.intel.com
Subject: Re: [block:for-3.14/core] kernel BUG at fs/bio.c:1748

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@...el.com>
CC: Kent Overstreet <kmo@...erainc.com>
CC: Jens Axboe <axboe@...nel.dk>
CC: Chris Mason <clm@...com>
Signed-off-by: Muthukumar Ratty <muthur@...il.com>

-----------
 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_put(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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