linux-ext4 - Re: [PATCH v4 2/4] jbd2: discard dirty data when forgetting an un-journalled buffer

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Date:   Sun, 10 Feb 2019 23:31:28 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     "zhangyi (F)" <yi.zhang@...wei.com>
CC:     <linux-ext4@...r.kernel.org>, <jack@...e.cz>,
        <adilger.kernel@...ger.ca>, <miaoxie@...wei.com>
Subject: Re: [PATCH v4 2/4] jbd2: discard dirty data when forgetting an
 un-journalled buffer

On Wed, Jan 30, 2019 at 02:49:38PM +0800, zhangyi (F) wrote:
> We do not unmap and clear dirty flag when forgetting a buffer without
> journal or does not belongs to any transaction, so the invalid dirty
> data may still be written to the disk later. It's fine if the
> corresponding block is never used before the next mount, and it's also
> fine that we invoke clean_bdev_aliases() related functions to unmap
> the block device mapping when re-allocating such freed block as data
> block. But this logic is somewhat fragile and risky that may lead to
> data corruption if we forget to clean bdev aliases. So, It's better to
> discard dirty data during forget time.
> 
> We have been already handled all the cases of forgetting journalled
> buffer, this patch deal with the remaining two cases.
> 
> - buffer is not journalled yet,
> - buffer is journalled but doesn't belongs to any transaction.
> 
> We invoke __bforget() instead of __brelese() when forgetting an
> un-journalled buffer in jbd2_journal_forget(). After this patch we can
> remove all clean_bdev_aliases() related calls in ext4.
> 
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: zhangyi (F) <yi.zhang@...wei.com>
> Reviewed-by: Jan Kara <jack@...e.cz>

Thanks, applied.

				- Ted