linux-kernel - Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache

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Message-ID: <3061888.dPHoQkWWFl@wuerfel>
Date:	Wed, 02 Mar 2016 11:55:12 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	"Darrick J. Wong" <darrick.wong@...cle.com>, axboe@...nel.dk,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	martin.petersen@...cle.com, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, shane.seymour@....com,
	bfields@...ldses.org, linux-fsdevel@...r.kernel.org,
	jlayton@...chiereds.net
Subject: Re: [PATCH v5.1 0/2] create BLKZEROOUT ioctl that invalidates page cache

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