Re: Re: Re: EXT4 regression caused 4eec7

[Dmitry Monakhov <dmonakhov@openvz.org>]

On Sun, 12 May 2013 13:05:00 +0000 (GMT), EUNBONG SONG <eunb.song@samsung.com> wrote:
> 
> 
> >> Since at this point it's safer to rollback the change and we can
> >> investigate more deeply how to fix it correctly for the next
> >> development cycle, this is the patch which I'm testing.
> 
> >>                     - Ted
> 
> > Hello, I've tested with your patch. But the same problem was reproduced.
> > Currently, I'm trying to git bisect. If i done git bisect, i will let you know.
> 
> Hi, I've done git bisect. and panic at jbd2_journal_put_journal_head() is caused by 
> ae4647fb7654676fc44a97e86eb35f9f06b99f66: "jbd2: reduce journal_head size."
OK that explains both regressions ext4/jbd2 and ext3/jbd(https://lkml.org/lkml/2013/5/10/434)
Probably some race because b_jlist accessed w/o lock some places. 
BUT i still can not reproduce original issue :(
I've tried all types of disks near me (ssd,hdd,usb-dongle),
What disk type you use? Is it reproducible on x86?
Please post following info:
#fdisk -l  $HDD
#hdparm -t $HDD
#df -h 
#cat /proc/mounts

> I write just code patch which revert ae4647fb7654676fc44a97e86eb35f9f06b99f66 because
> I don't know the root cause. 
> 
> 
> Signed-off-by: Eunbong Song <eunb.song@samsung.com>
> ---
>  include/linux/journal-head.h |   11 +++++++++--
>  1 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/journal-head.h b/include/linux/journal-head.h
> index 13a3da2..c18b46f 100644
> --- a/include/linux/journal-head.h
> +++ b/include/linux/journal-head.h
> @@ -31,14 +31,21 @@ struct journal_head {
>  	/*
>  	 * Journalling list for this buffer [jbd_lock_bh_state()]
>  	 */
> -	unsigned b_jlist:4;
> +	unsigned b_jlist;
>  
>  	/*
>  	 * This flag signals the buffer has been modified by
>  	 * the currently running transaction
>  	 * [jbd_lock_bh_state()]
>  	 */
> -	unsigned b_modified:1;
> +	unsigned b_modified;
> +
> +	/*
> +	 * This feild tracks the last transaction id in which this buffer
> +	 * has been cowed
> +	 * [jbd_lock_bh_state()]
> +	 */
> +	tid_t b_cow_tid;
>  
>  	/*
>  	 * Copy of the buffer data frozen for writing to the log.
> -- 
> 1.7.0.4
> 
> 
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