linux-ext4 - Re: [PATCH v3 1/5] ext4: abort the filesystem if failed to async write metadata buffer

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Message-ID: <20200807174925.GV7657@mit.edu>
Date:   Fri, 7 Aug 2020 13:49:25 -0400
From:   tytso@....edu
To:     "zhangyi (F)" <yi.zhang@...wei.com>
Cc:     <linux-ext4@...r.kernel.org>, <jack@...e.cz>,
        <adilger.kernel@...ger.ca>, <zhangxiaoxu5@...wei.com>,
        <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v3 1/5] ext4: abort the filesystem if failed to async
 write metadata buffer

On Sat, Jun 20, 2020 at 10:54:23AM +0800, zhangyi (F) wrote:
> There is a risk of filesystem inconsistency if we failed to async write
> back metadata buffer in the background. Because of current buffer's end
> io procedure is handled by end_buffer_async_write() in the block layer,
> and it only clear the buffer's uptodate flag and mark the write_io_error
> flag, so ext4 cannot detect such failure immediately. In most cases of
> getting metadata buffer (e.g. ext4_read_inode_bitmap()), although the
> buffer's data is actually uptodate, it may still read data from disk
> because the buffer's uptodate flag has been cleared. Finally, it may
> lead to on-disk filesystem inconsistency if reading old data from the
> disk successfully and write them out again.
> 
> This patch detect bdev mapping->wb_err when getting journal's write
> access and mark the filesystem error if bdev's mapping->wb_err was
> increased, this could prevent further writing and potential
> inconsistency.
> 
> Signed-off-by: zhangyi (F) <yi.zhang@...wei.com>
> Suggested-by: Jan Kara <jack@...e.cz>

Thanks, applied.

							- Ted