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

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Message-ID: <20190813104616.GA4198@poseidon.bobrowski.net>
Date:   Tue, 13 Aug 2019 20:46:18 +1000
From:   Matthew Bobrowski <mbobrowski@...browski.org>
To:     Christoph Hellwig <hch@...radead.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 10:18:39AM -0700, Christoph Hellwig wrote:
> 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.

As mentioned in my other email (4/5), this is callback needs to remain.

--M