From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RESEND] [PATCH] block: create ioctl to discard-or-zeroout a range of blocks Date: Thu, 29 Jan 2015 11:02:58 +0100 Message-ID: <2747023.BlTyJ4fNVf@wuerfel> References: <20150129020025.GE9981@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20150129020025.GE9981@birch.djwong.org> Sender: linux-kernel-owner@vger.kernel.org To: "Darrick J. Wong" Cc: Jens Axboe , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Jeff Layton , "J. Bruce Fields" List-Id: linux-api@vger.kernel.org On Wednesday 28 January 2015 18:00:25 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. > > This patch depends on "block: Add discard flag to > blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. > > Signed-off-by: Darrick J. Wong > Would this work ok for devices that fill discarded areas with all-ones instead of all-zeroes? I believe SD cards can do either. Arnd