linux-ext4 - Re: [PATCH 1/2] ext4: call ext4_error_inode() if jbd2_journal_dirty

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Date:	Mon, 2 Dec 2013 16:30:50 +0100
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH 1/2] ext4: call ext4_error_inode() if
 jbd2_journal_dirty_metadata() fails

On Mon 02-12-13 09:45:01, Ted Tso wrote:
> While it's true that errors can only happen if there is a bug in
> jbd2_journal_dirty_metadata(), if a bug does happen, we need to halt
> the kernel or remount the file system read-only in order to avoid
> further data loss.  The ext4_journal_abort_handle() function doesn't
> do any of this, and while it's likely that this call (since it doesn't
> adjust refcounts) will likely result in the file system eventually
> deadlocking since the current transaction will never be able to close,
> it's much cleaner to call let ext4's error handling system deal with
> this situation.
> 
> There's a separate bug here which is that if certain jbd2 errors
> errors occur and file system is mounted errors=continue, the file
> system will probably eventually end grind to a halt as described
> above.  But things have been this way in a long time, and usually when
> we have these sorts of errors it's pretty much a disaster --- and
> that's why the jbd2 layer aggressively retries memory allocations,
> which is the most likely cause of these jbd2 errors.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> Cc: stable@...r.kernel.org
  The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/ext4_jbd2.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
> index 17ac112..3fe29de 100644
> --- a/fs/ext4/ext4_jbd2.c
> +++ b/fs/ext4/ext4_jbd2.c
> @@ -259,6 +259,15 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
>  		if (WARN_ON_ONCE(err)) {
>  			ext4_journal_abort_handle(where, line, __func__, bh,
>  						  handle, err);
> +			ext4_error_inode(inode, where, line,
> +					 bh->b_blocknr,
> +					 "journal_dirty_metadata failed: "
> +					 "handle type %u started at line %u, "
> +					 "credits %u/%u, errcode %d",
> +					 handle->h_type,
> +					 handle->h_line_no,
> +					 handle->h_requested_credits,
> +					 handle->h_buffer_credits, err);
>  		}
>  	} else {
>  		if (inode)
> -- 
> 1.8.5.rc3.362.gdf10213
> 
> --
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-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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