On Sun, May 12, 2013 at 07:04:45PM -0700, Tony Luck wrote:
> On Sat, May 11, 2013 at 12:52 AM, Dmitry Monakhov <dmonakhov@xxxxxxxxxx> wrote:.
> > What was page_size and fsblock size?
>
> CONFIG_IA64_PAGE_SIZE_64KB=y
>
> fsblock size is whatever is the default for SLES11SP2 on ia64 - which
> tool will tell me?
>
> My git bisect finally competed and points the a finger at:
>
> bisect> git bisect good
> ae4647fb7654676fc44a97e86eb35f9f06b99f66 is first bad commit
> commit ae4647fb7654676fc44a97e86eb35f9f06b99f66
> Author: Jan Kara <jack@xxxxxxx>
> Date: Fri Apr 12 00:03:42 2013 -0400
>
> jbd2: reduce journal_head size
>
> Remove unused t_cow_tid field (ext4 copy-on-write support doesn't seem
> to be happening) and change b_modified and b_jlist to bitfields thus
> saving 8 bytes in the structure.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
>
> :040000 040000 c39ece4341894b3daf84764ba425a87ffb90fe50
> d4e8d9185c2a1b740c235ca8ed05d496a442fce3 M include
Hi all,
First of all I couldn't reproduce this regression in my sand box. So
the following speculation is only my guess. I suspect that the commit
(ae4647fb) isn't root cause. It just uncover a potential bug that has
been there for a long time. I look at the code, and found two
suspicious stuff in jbd2. The first one is in do_get_write_access().
In this function we forgot to lock bh state when we check b_jlist ==
BJ_Shadow. I generate a patch to fix it, and I really think it is the
root cause. Further, in __journal_remove_journal_head() we check
b_jlist == BJ_None. But, when this function is called, bh state won't
be locked sometimes. So I suspect this is why we hit a BUG in
jbd2_journal_put_journal_head(). But I don't have a good solution to
fix this until now because I don't know whether we need to lock bh state
here, or maybe we should remove this assertation.
So, generally, Tony, Eunbong, could you please try the following patch?
Thanks in advance,
- Zheng
Subject: [PATCH] jbd2: lock bh state when check b_jlist == BJ_Shadow
From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
When we try to check b_jlist's value we need to lock bh state. But in
do_get_write_access when we check b_jlist == BJ_Shadow we won't lock bh
state. So fix it.
Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
---
fs/jbd2/transaction.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 10f524c..a800513 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -761,16 +761,18 @@ repeat:
wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
JBUFFER_TRACE(jh, "on shadow: sleep");
- jbd_unlock_bh_state(bh);
/* commit wakes up all shadow buffers after IO */
- for ( ; ; ) {
- prepare_to_wait(wqh, &wait.wait,
- TASK_UNINTERRUPTIBLE);
+ do {
if (jh->b_jlist != BJ_Shadow)
break;
+ prepare_to_wait(wqh, &wait.wait,
+ TASK_UNINTERRUPTIBLE);
+ jbd_unlock_bh_state(bh);
schedule();
- }
- finish_wait(wqh, &wait.wait);
+ finish_wait(wqh, &wait.wait);
+ jbd_lock_bh_state(bh);
+ } while (1);
+ jbd_unlock_bh_state(bh);
goto repeat;
}
--
1.7.12.rc2.18.g61b472e
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
