linux-kernel - Re: [PATCH 4/5] jbd: fix error handling for checkpoint io

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Date:	Tue, 3 Jun 2008 10:02:19 +0200
From:	Jan Kara <jack@...e.cz>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc:	akpm@...ux-foundation.org, sct@...hat.com, adilger@...sterfs.com,
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	jbacik@...hat.com, cmm@...ibm.com, tytso@....edu,
	sugita <yumiko.sugita.yf@...achi.com>,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>
Subject: Re: [PATCH 4/5] jbd: fix error handling for checkpoint io

On Tue 03-06-08 13:40:25, Hidehiro Kawai wrote:
> Subject: [PATCH 4/5] jbd: fix error handling for checkpoint io
> 
> When a checkpointing IO fails, current JBD code doesn't check the
> error and continue journaling.  This means latest metadata can be
> lost from both the journal and filesystem.
> 
> This patch leaves the failed metadata blocks in the journal space
> and aborts journaling in the case of log_do_checkpoint().
> To achieve this, we need to do:
> 
> 1. don't remove the failed buffer from the checkpoint list where in
>    the case of __try_to_free_cp_buf() because it may be released or
>    overwritten by a later transaction
> 2. log_do_checkpoint() is the last chance, remove the failed buffer
>    from the checkpoint list and abort the journal
> 3. when checkpointing fails, don't update the journal super block to
>    prevent the journaled contents from being cleaned.  For safety,
>    don't update j_tail and j_tail_sequence either
> 4. when checkpointing fails, notify this error to the ext3 layer so
>    that ext3 don't clear the needs_recovery flag, otherwise the
>    journaled contents are ignored and cleaned in the recovery phase
> 5. if the recovery fails, keep the needs_recovery flag
> 6. prevent cleanup_journal_tail() from being called between
>    __journal_drop_transaction() and journal_abort() (a race issue
>    between journal_flush() and __log_wait_for_space()
> 
> Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
  You can add:
  Acked-by: Jan Kara <jack@...e.cz>

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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