linux-ext4 - Re: [PATCH] ext4: fix a bug in ext4_wait_for_tail_page

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Message-ID: <20190917153140.GF6762@mit.edu>
Date:   Tue, 17 Sep 2019 11:31:40 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     yangerkun <yangerkun@...wei.com>
Cc:     jack@...e.cz, linux-ext4@...r.kernel.org, yi.zhang@...wei.com,
        houtao1@...wei.com
Subject: Re: [PATCH] ext4: fix a bug in ext4_wait_for_tail_page_commit

On Tue, Sep 17, 2019 at 04:48:14PM +0800, yangerkun wrote:
> No need to wait when offset equals to 0. And it will trigger a bug since
> the latter __ext4_journalled_invalidatepage can free the buffers but leave
> page still dirty.

That's only true if the block size == the page size, no?  If the
offset is zero and the block size is 1k, we still need to wait.
Shouldn't the better fix be:

> -	if (offset > PAGE_SIZE - i_blocksize(inode))
> +	if (offset >= PAGE_SIZE - i_blocksize(inode))

  	   	      		- Ted