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

[tytso@mit.edu]

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@huawei.com>
> Suggested-by: Jan Kara <jack@suse.cz>

Thanks, applied.

							- Ted