linux-kernel - Re: [PATCH v4] block: create ioctl to discard-or-zeroout a range of blocks

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Message-ID: <20151208024015.GA18458@infradead.org>
Date:	Mon, 7 Dec 2015 18:40:15 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@...radead.org>,
	"Seymour, Shane M" <shane.seymour@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	"martin.petersen@...cle.com" <martin.petersen@...cle.com>
Subject: Re: [PATCH v4] block: create ioctl to discard-or-zeroout a range of
 blocks

On Fri, Nov 13, 2015 at 02:01:43PM -0800, Darrick J. Wong wrote:
> Create a new ioctl to expose the block layer's newfound ability to
> issue either a zeroing discard, a WRITE SAME with a zero page, or a
> regular write with the zero page.  This BLKZEROOUT2 ioctl takes
> {start, length, flags} as parameters.  So far, the only flag available
> is to enable the zeroing discard part -- without it, the call invokes
> the old BLKZEROOUT behavior.  start and length have the same meaning
> as in BLKZEROOUT.
> 
> Furthermore, because BLKZEROOUT2 issues commands directly to the
> storage device, we must invalidate the page cache (as a regular
> O_DIRECT write would do) to avoid returning stale cache contents at a
> later time.

So does BLKZEROOUT.  Seems like adding the cache invalidation should
be one patch and the ioctl another one.  Otherwise this looks fine
except that I kinda hate BLKZEROOUT2 name, but can't come up with
anything better.
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