linux-ext4 - Re: [PATCH 2/5] ext4: move inode extension/truncate code out from ext4_iomap

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Message-ID: <20190812171839.GC24564@infradead.org>
Date:   Mon, 12 Aug 2019 10:18:39 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Bobrowski <mbobrowski@...browski.org>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        jack@...e.cz, tytso@....edu, riteshh@...ux.ibm.com
Subject: Re: [PATCH 2/5] ext4: move inode extension/truncate code out from
 ext4_iomap_end()

On Mon, Aug 12, 2019 at 10:52:53PM +1000, Matthew Bobrowski wrote:
> In preparation for implementing the direct IO write code path modifications
> that make us of iomap infrastructure we need to move out the inode
> extension/truncate code from ext4_iomap_end() callback. For direct IO, if the
> current code remained it would behave incorrectly. If we update the inode size
> prior to converting unwritten extents we run the risk of allowing a racing
> direct IO read operation to find unwritten extents before they are converted.
> 
> The inode extension/truncate has been moved out into a new function
> ext4_handle_inode_extension(). This will be used by both direct IO and DAX
> code paths if the write results with the inode being extended.

ext4_iomap_end is empty now, so you could as well remove it entirely.