From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David Woodhouse" Subject: Re: TRIM vs UNMAP vs WRITE SAME and thin devices Date: Sat, 7 Feb 2009 23:36:07 -0000 (UTC) Message-ID: <6e1133942a9f20e058e117a24fad9199.squirrel@baythorne.infradead.org> References: <20090123041558.GC24652@parisc-linux.org> <4979AF62.7070409@redhat.com> <1232721777.4430.7.camel@macbook.infradead.org> <498DA052.6090605@redhat.com> <20090207224722.GA31509@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: 8bit Cc: "Ric Wheeler" , "David Woodhouse" , "James Bottomley" , "Martin K. Petersen" , "Jeff Garzik" , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, "IDE/ATA development list" To: "Matthew Wilcox" Return-path: In-Reply-To: <20090207224722.GA31509@parisc-linux.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org > On Sat, Feb 07, 2009 at 09:53:06AM -0500, Ric Wheeler wrote: >> I have been poked at by some vendors about the status of our support for >> the virtually/thinly provisioned luns since they are getting close to >> being able to test with real devices. >> >> My quick summary is that we most of the work so far has been done >> without any real hardware to play with - in 2.6.29-rc3, I don't see any >> low level ATA or SCSI bits that turn requests tagged with REQ_DISCARD >> into the specific ATA or SCSI commands. Did I miss something & if not, >> do we have plans to push anything upstream soonish? > > Bearing in mind that I'm now three weeks behind on email, you might want > to look at > http://git.kernel.org/?p=linux/kernel/git/willy/ssd.git;a=shortlog;h=trim-20081231 > which has at least one known bug (fixed by Dave Woodhouse and Ben > Herrenschmidt). I'll be able to give a more coherent answer in a few > days. Or maybe Dave will beat me to it ;-) Ben's suggestion was that the IDE core wouldn't be sending the payload of the command because it looks at the R/W bit... which is clear (read) in our discard requests ATM. Making them appear to be writes is simple enough though. I gave an updated test kernel to the Sandisk folks but haven't got results back from them yet.