From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 27 Mar 2017 16:57:40 +0200 From: Christoph Hellwig To: Mike Snitzer Cc: Christoph Hellwig , Christoph Hellwig , axboe@kernel.dk, martin.petersen@oracle.com, agk@redhat.com, shli@kernel.org, philipp.reisner@linbit.com, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, drbd-dev@lists.linbit.com, dm-devel@redhat.com, linux-raid@vger.kernel.org Subject: Re: RFC: always use REQ_OP_WRITE_ZEROES for zeroing offload Message-ID: <20170327145740.GB24952@lst.de> References: <20170323143341.31549-1-hch@lst.de> <20170323155410.GD1138@soda.linbit> <20170327091056.GB6879@infradead.org> <20170327140307.GA13020@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170327140307.GA13020@redhat.com> List-ID: On Mon, Mar 27, 2017 at 10:03:07AM -0400, Mike Snitzer wrote: > By "you" I assume you're referring to Lars? Yes. > Lars' approach for discard, > when drbd is layered on dm-thinp, feels over-engineered. Not his fault, > the way discard and zeroing got conflated certainly lends itself to > these ugly hacks. SO I do appreciate that for anything to leverage > discard_zeroes_data it needs to be reliable. Which runs counter to how > discard was implemented (discard may get silently dropped!) But that is > why dm-thinp doesn't advertise dzd. Anyway... That's exactly what this series does - remove discard_zeroes_data and use the new REQ_OP_WRITE_ZEROES for anything that wants zeroing offload. > As for the blkdev_issue_zeroout() resorting to manually zeroing the > range, if the discard fails or dzd not supported, that certainly > requires DM thinp to implement manual zeroing of the head and tail of > the range if partial blocks are being zeroed. So I welcome any advances > there. It is probably something that is best left to Joe or myself to > tackle. But I'll gladly accept patches ;) Ok, I'll happily leave this to the two of you..