linux-ext4 - Re: [PATCH v2] ext4, jbd2: ensure entering into panic after recording an error in superblock

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Date:	Sun, 18 Oct 2015 19:38:04 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Daeho Jeong <daeho.jeong@...sung.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2] ext4, jbd2: ensure entering into panic after
 recording an error in superblock

On Mon, Oct 12, 2015 at 11:19:19AM +0900, Daeho Jeong wrote:
> If a EXT4 filesystem utilizes JBD2 journaling and an error occurs, the
> journaling will be aborted first and the error number will be recorded
> into JBD2 superblock and, finally, the system will enter into the
> panic state in "errors=panic" option.  But, in the rare case, this
> sequence is little twisted like the below figure and it will happen
> that the system enters into panic state, which means the system reset
> in mobile environment, before completion of recording an error in the
> journal superblock. In this case, e2fsck cannot recognize that the
> filesystem failure occurred in the previous run and the corruption
> wouldn't be fixed.
> 
> Task A                        Task B
> ext4_handle_error()
> -> jbd2_journal_abort()
>   -> __journal_abort_soft()
>     -> __jbd2_journal_abort_hard()
>     | -> journal->j_flags |= JBD2_ABORT;
>     |
>     |                         __ext4_abort()
>     |                         -> jbd2_journal_abort()
>     |                         | -> __journal_abort_soft()
>     |                         |   -> if (journal->j_flags & JBD2_ABORT)
>     |                         |           return;
>     |                         -> panic()
>     |
>     -> jbd2_journal_update_sb_errno()
> 
> Tested-by: Hobin Woo <hobin.woo@...sung.com>
> Signed-off-by: Daeho Jeong <daeho.jeong@...sung.com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>

Applied, thanks.

						- Ted
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