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To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@infradead.org>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-api@vger.kernel.org, Jeff Layton <jlayton@poochiereds.net>,
        "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: [RESEND] [PATCH] block: create ioctl to discard-or-zeroout a range of blocks
From: "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle
References: <20150129020025.GE9981@birch.djwong.org>
Date: Thu, 29 Jan 2015 19:48:06 -0500
In-Reply-To: <20150129020025.GE9981@birch.djwong.org> (Darrick J. Wong's
	message of "Wed, 28 Jan 2015 18:00:25 -0800")
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>>>>> "Darrick" == Darrick J Wong <darrick.wong@oracle.com> writes:

Darrick> Create a new ioctl to expose the block layer's newfound ability
Darrick> to issue either a zeroing discard, a WRITE SAME with a zero
Darrick> page, or a regular write with the zero page.  This BLKZEROOUT2
Darrick> ioctl takes {start, length, flags} as parameters.  So far, the
Darrick> only flag available is to enable the zeroing discard part --
Darrick> without it, the call invokes the old BLKZEROOUT behavior.
Darrick> start and length have the same meaning as in BLKZEROOUT.

Darrick> Furthermore, because BLKZEROOUT2 issues commands directly to
Darrick> the storage device, we must invalidate the page cache (as a
Darrick> regular O_DIRECT write would do) to avoid returning stale cache
Darrick> contents at a later time.

Looks good to me, Darrick.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering