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

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Date:	Sun, 5 Jan 2014 17:46:39 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Muthu Kumar <muthu.lkml@...il.com>
Cc:	Kent Overstreet <kmo@...erainc.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

Hi Muthu,

On Fri, Jan 03, 2014 at 11:51:31AM -0800, Muthu Kumar wrote:
> Looks like Kent missed the btrfs endio in the original commit. How
> about this patch:
> 
> ---------
> 
> In btrfs_end_bio, call bio_endio_nodec on the restored bio so the
> bi_remaining is accounted for correctly.
> 
> Reported-by: fengguang.wu@...el.com
> Cc: Kent Overstreet <kmo@...erainc.com>
> CC: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Muthukumar Ratty <muthur@...il.com>
> --------
> 
>  fs/btrfs/volumes.c |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index f2130de..edfed52 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -5316,7 +5316,11 @@ static void btrfs_end_bio(struct bio *bio, int err)
>                 }
>                 kfree(bbio);
> 
> -               bio_endio(bio, err);
> +                /*
> +                 * Call endio_nodec on the restored bio so the bi_remaining is
> +                 * accounted for correctly
> +                 */
> +               bio_endio_nodec(bio, err);
>         } else if (!is_orig_bio) {
>                 bio_put(bio);
>         }
 
Interestingly, the BUG message disappeared but it blocks the test run.
In the end, the test watchdog reboots the machine with SysRq:

        2014-01-04 23:13:02 mount -t btrfs /dev/vda /fs/vda
        [   20.184264] btrfs: device fsid f0e06999-0518-47e0-a622-21b8749438be devid 1 transid 4 /dev/vda
        [   20.186552] btrfs: disk space caching is enabled
        [  131.360457] random: nonblocking pool is initialized
==>     [ 1465.069342] SysRq : Emergency Sync
==>     [ 1475.071055] SysRq : Resetting

Attached is the full dmesg for a good run (v3.13-rc7) and a bad run
(this patch).

Thanks,
Fengguang

View attachment "dmesg-v3.13-rc7" of type "text/plain" (70993 bytes)

View attachment "dmesg-bio_endio_nodec" of type "text/plain" (63820 bytes)