[Ocfs2-devel] [PATCH] ocfs2/journal: fix umount hang after flushing journal failure

[Joseph Qi]

According to the call trace, umount hangs because ocfs2_commit_thread
can't exit. So I think we'd better put the logic into ocfs2_commit_thread,
which can be align with kthread_should_stop to identify the case.

Thanks,
Joseph

On 17/1/7 20:01, Gechangwei wrote:
>
> Hi,
>
> When journal flushing in ocfs2_commit_cache() fails, following umount 
> procedure at stage of shutting journal may be blocked due to non-zero 
> transactions number.
>
> Once jbd2_journal_flush() fails, the journal will be marked as ABORT 
> state inner JBD2. There is no way to come back afterwards.
>
> So there is no chance to set transactions number to zero, thus, 
> shutting journal may be blocked .
>
>
> ocfs2_commit_thread()
>
>     ocfs2_commit_cache()
>
>         jbd2_journal_flush() -> failure takes journal into ABORT 
> state, thus, transaction number will never set to zero
>
>
> The back trace is cited blow:
>
> [<ffffffff8109de0c>] kthread_stop+0x4c/0x150
> [<ffffffffc056a887>] ocfs2_journal_shutdown+0xa7/0x400 [ocfs2]
> [<ffffffffc059fbde>] ocfs2_dismount_volume+0xbe/0x4a0 [ocfs2]
> [<ffffffffc059fff7>] ocfs2_put_super+0x37/0xb0 [ocfs2]
> [<ffffffff8120534e>] generic_shutdown_super+0x7e/0x110
> [<ffffffff81205410>] kill_block_super+0x30/0x80
> [<ffffffff81205669>] deactivate_locked_super+0x59/0x90
> [<ffffffff812062ee>] deactivate_super+0x4e/0x70
> [<ffffffff81222423>] cleanup_mnt+0x43/0x90
> [<ffffffff812224c2>] __cleanup_mnt+0x12/0x20
> [<ffffffff8109c247>] task_work_run+0xb7/0xf0
> [<ffffffff81016f7c>] do_notify_resume+0x8c/0xa0
> [<ffffffff817f8384>] int_signal+0x12/0x17
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> Through crash debug tool, It can seen that j_num_trans field is set to 2.
>
> struct ocfs2_journal {
>   j_state = OCFS2_JOURNAL_IN_SHUTDOWN,
>   j_journal = 0xffff8800b4926000,
>   j_inode = 0xffff880122aba298,
>   j_osb = 0xffff880093caa000,
>   j_bh = 0xffff8800a09df888,
>   j_num_trans = {
>     counter = 0x2
>   },
>   j_lock = {
>     {
>       rlock = {
>         raw_lock = {
>           {
>
>
> To solve this issue, I propose a patch. Any comments will be welcomed.
>
> Since journal has been marked as ABORT and flushing journal failure 
> will free all corresponding buffer heads, it will be safe to directly 
> set transactions number to zero.
>
>
> From 98f42f5f52851ed84eb372a3e09a413a30ea2664 Mon Sep 17 00:00:00 2001
> From: gechangwei <ge.changwei at h3c.com>
> Date: Sat, 7 Jan 2017 19:48:13 +0800
> Subject: [PATCH] fix umount hang after flushing journal failure
>
> Signed-off-by: gechangwei <ge.changwei at h3c.com>
> ---
>  fs/ocfs2/journal.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
> index a244f14..dab2094 100644
> --- a/fs/ocfs2/journal.c
> +++ b/fs/ocfs2/journal.c
> @@ -326,6 +326,7 @@ static int ocfs2_commit_cache(struct ocfs2_super *osb)
>      status = jbd2_journal_flush(journal->j_journal);
>      jbd2_journal_unlock_updates(journal->j_journal);
>      if (status < 0) {
> +        atomic_set(&journal->j_num_trans, 0);
>          up_write(&journal->j_trans_barrier);
>          mlog_errno(status);
>          goto finally;
> -- 
> 2.5.1.windows.1
>
>
> -------------------------------------------------------------------------------------------------------------------------------------
> 本邮件及其附件含有杭州华三通信技术有限公司的保密信息，仅限于发送给上面地址中列出
> 的个人或群组。禁止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、
> 或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本
> 邮件！
> This e-mail and its attachments contain confidential information from 
> H3C, which is
> intended only for the person or entity whose address is listed above. 
> Any use of the
> information contained herein in any way (including, but not limited 
> to, total or partial
> disclosure, reproduction, or dissemination) by persons other than the 
> intended
> recipient(s) is prohibited. If you receive this e-mail in error, 
> please notify the sender
> by phone or email immediately and delete it! 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://oss.oracle.com/pipermail/ocfs2-devel/attachments/20170110/51b7989e/attachment.html