From: Arnd Bergmann <arnd@arndb.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>, axboe@kernel.dk,
        akpm@linux-foundation.org, torvalds@linux-foundation.org,
        martin.petersen@oracle.com, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org, shane.seymour@hpe.com,
        bfields@fieldses.org, linux-fsdevel@vger.kernel.org,
        jlayton@poochiereds.net
Subject: Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache
Date: Wed, 02 Mar 2016 11:55:12 +0100
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On Wednesday 02 March 2016 01:44:16 Christoph Hellwig wrote:
> On Wed, Mar 02, 2016 at 10:15:02AM +0100, Arnd Bergmann wrote:
> > I'm missing the background on this, just saw the patch fly by,
> > so sorry if this has been asked before:
> > 
> > Why do you want to invalidate the cache? Is this to save RAM
> > or is something else going to write here and you have to invalidate
> > it for correctness?
> 
> BLKZEROOUT can be though as a direct I/O operation - it issues a 
> WRITE SAME (or similar) command straight to the device to zero
> the specified range.  If there was cached data for this range it would
> now be stale.

Ok, got it. Thanks,

	Arnd