From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: block: fix alignment_offset math that assumes io_min is a power-of-2 Date: Wed, 8 Oct 2014 18:41:50 -0400 Message-ID: <20141008224149.GB15590@redhat.com> References: <1412805952-15316-1-git-send-email-snitzer@redhat.com> <5435B6C0.8020704@kernel.dk> <20141008222841.GA15345@redhat.com> <5435BCD5.9050306@kernel.dk> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <5435BCD5.9050306@kernel.dk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Jens Axboe Cc: dm-devel@redhat.com, linux-kernel@vger.kernel.org, martin.petersen@oracle.com List-Id: dm-devel.ids T24gV2VkLCBPY3QgMDggMjAxNCBhdCAgNjozOHBtIC0wNDAwLApKZW5zIEF4Ym9lIDxheGJvZUBr ZXJuZWwuZGs+IHdyb3RlOgoKPiBPbiAxMC8wOC8yMDE0IDA0OjI4IFBNLCBNaWtlIFNuaXR6ZXIg d3JvdGU6Cj4gPiBPbiBXZWQsIE9jdCAwOCAyMDE0IGF0ICA2OjEycG0gLTA0MDAsCj4gPiBKZW5z IEF4Ym9lIDxheGJvZUBrZXJuZWwuZGs+IHdyb3RlOgo+ID4gCj4gPj4gT24gMTAvMDgvMjAxNCAw NDowNSBQTSwgTWlrZSBTbml0emVyIHdyb3RlOgo+ID4+PiBUaGUgbWF0aCBpbiBib3RoIGJsa19z dGFja19saW1pdHMoKSBhbmQgcXVldWVfbGltaXRfYWxpZ25tZW50X29mZnNldCgpCj4gPj4+IGFz c3VtZSB0aGF0IGEgYmxvY2sgZGV2aWNlJ3MgaW9fbWluIChha2EgbWluaW11bV9pb19zaXplKSBp cyBhbHdheXMgYQo+ID4+PiBwb3dlci1vZi0yLiAgRml4IHRoZSBtYXRoIHN1Y2ggdGhhdCBpdCB3 b3JrcyBmb3Igbm9uLXBvd2VyLW9mLTIgaW9fbWluLgo+ID4+Pgo+ID4+PiBUaGlzIGlzc3VlIChv ZiBhbGlnbm1lbnRfb2Zmc2V0ICE9IDApIGJlY2FtZSBhcHBhcmVudCB3aGVuIHRlc3RpbmcKPiA+ Pj4gZG0tdGhpbnAgd2l0aCBhIHRoaW5wIGJsb2Nrc2l6ZSB0aGF0IG1hdGNoZXMgYSBSQUlENiBz dHJpcGVzaXplIG9mCj4gPj4+IDEyODBLLiAgQ29tbWl0IGZkZmI0YzhjMSAoImRtIHRoaW46IHNl dCBtaW5pbXVtX2lvX3NpemUgdG8gcG9vbCdzIGRhdGEKPiA+Pj4gYmxvY2sgc2l6ZSIpIHVubG9j a2VkIHRoZSBwb3RlbnRpYWwgZm9yIGFsaWdubWVudF9vZmZzZXQgIT0gMCBkdWUgdG8KPiA+Pj4g dGhlIGRtLXRoaW4tcG9vbCdzIGlvX21pbiBwb3NzaWJseSBiZWluZyBhIG5vbi1wb3dlci1vZi0y Lgo+ID4+Cj4gPj4gV2VsbCB0aGF0IHN1Y2tzLCBBTkQgd2l0aCBhIG1hc2sgaXMgY29uc2lkZXJh Ymx5IGNoZWFwZXIgdGhhbiBhIE1PRC4uLgo+ID4gCj4gPiBZZWFoLCBjZXJ0YWlubHkgZG9lcyBz dWNrIChwbGVhc2Ugbm90ZSB2MiB0aGF0IEkganVzdCBzZW50KS4gIFRoZSBNT0RzCj4gPiBzaG91 bGRuJ3Qga2lsbCB1cywgdGhlc2UgZnVuY3Rpb25zIGFyZW4ndCBjYWxsZWQgaW4gYW55IHJlYWwg aG90IHBhdGguCj4gPiBBIHN0b3JtIGF0IGJvb3QgbWF5YmUuLiBvciBTQ1NJIHJlc2NhbiBidXQu Li4KPiAKPiBJIGhhZCBpdCBtaXhlZCB1cCB3aXRoIHRoZSByZWNlbnQgYmxrX21heF9zaXplX29m ZnNldCgpIC0geW91IGFyZSByaWdodCwKPiB0aGlzIGlzIG5vdCBpbiBhIGhvdCBwYXRoLiBGb3Ig dGhhdCBjYXNlLCBJIGRvbid0IHJlYWxseSBjYXJlLCBpdCdzIGZpbmUuCj4gCj4gSXMgdjIgcnVu dGltZSB0ZXN0ZWQ/CgpZZXMuCgpIZXJlIGlzIHRoZSBETSBzdGFjayBmb3IgYW4gbHZtIGNyZWF0 ZWQgZG0tdGhpbi1wb29sIChkbS01KS4KCiMgbHNibGsgL2Rldi9za2QwCk5BTUUgICAgICAgICAg ICAgICAgICAgIE1BSjpNSU4gUk0gICBTSVpFIFJPIFRZUEUgTU9VTlRQT0lOVApza2QwICAgICAg ICAgICAgICAgICAgICAyNTI6MCAgICAwIDc0NS4zRyAgMCBkaXNrIArilJzilIBicmlja3MtbXlw b29sX3RtZXRhICAgMjUzOjIgICAgMCAgMTUuOEcgIDAgbHZtICAK4pSCIOKUlOKUgGJyaWNrcy1t eXBvb2wtdHBvb2wgMjUzOjQgICAgMCAgIDUxMkcgIDAgbHZtICAK4pSCICAg4pSU4pSAYnJpY2tz LW15cG9vbCAgICAgMjUzOjUgICAgMCAgIDUxMkcgIDAgbHZtICAK4pSU4pSAYnJpY2tzLW15cG9v bF90ZGF0YSAgIDI1MzozICAgIDAgICA1MTJHICAwIGx2bSAgCiAg4pSU4pSAYnJpY2tzLW15cG9v bC10cG9vbCAyNTM6NCAgICAwICAgNTEyRyAgMCBsdm0gIAogICAg4pSU4pSAYnJpY2tzLW15cG9v bCAgICAgMjUzOjUgICAgMCAgIDUxMkcgIDAgbHZtICAKCkJlZm9yZSBwYXRjaDoKIyBjYXQgL3N5 cy9ibG9jay9kbS01L2FsaWdubWVudF9vZmZzZXQKMTA0ODU3NgoKQWZ0ZXIgcGF0Y2g6CiMgY2F0 IC9zeXMvYmxvY2svZG0tNS9hbGlnbm1lbnRfb2Zmc2V0IAowCgotLQpkbS1kZXZlbCBtYWlsaW5n IGxpc3QKZG0tZGV2ZWxAcmVkaGF0LmNvbQpodHRwczovL3d3dy5yZWRoYXQuY29tL21haWxtYW4v bGlzdGluZm8vZG0tZGV2ZWw= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754798AbaJHWrN (ORCPT ); Wed, 8 Oct 2014 18:47:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16185 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbaJHWrK (ORCPT ); Wed, 8 Oct 2014 18:47:10 -0400 Date: Wed, 8 Oct 2014 18:41:50 -0400 From: Mike Snitzer To: Jens Axboe Cc: linux-kernel@vger.kernel.org, dm-devel@redhat.com, martin.petersen@oracle.com Subject: Re: block: fix alignment_offset math that assumes io_min is a power-of-2 Message-ID: <20141008224149.GB15590@redhat.com> References: <1412805952-15316-1-git-send-email-snitzer@redhat.com> <5435B6C0.8020704@kernel.dk> <20141008222841.GA15345@redhat.com> <5435BCD5.9050306@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5435BCD5.9050306@kernel.dk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 08 2014 at 6:38pm -0400, Jens Axboe wrote: > On 10/08/2014 04:28 PM, Mike Snitzer wrote: > > On Wed, Oct 08 2014 at 6:12pm -0400, > > Jens Axboe wrote: > > > >> On 10/08/2014 04:05 PM, Mike Snitzer wrote: > >>> The math in both blk_stack_limits() and queue_limit_alignment_offset() > >>> assume that a block device's io_min (aka minimum_io_size) is always a > >>> power-of-2. Fix the math such that it works for non-power-of-2 io_min. > >>> > >>> This issue (of alignment_offset != 0) became apparent when testing > >>> dm-thinp with a thinp blocksize that matches a RAID6 stripesize of > >>> 1280K. Commit fdfb4c8c1 ("dm thin: set minimum_io_size to pool's data > >>> block size") unlocked the potential for alignment_offset != 0 due to > >>> the dm-thin-pool's io_min possibly being a non-power-of-2. > >> > >> Well that sucks, AND with a mask is considerably cheaper than a MOD... > > > > Yeah, certainly does suck (please note v2 that I just sent). The MODs > > shouldn't kill us, these functions aren't called in any real hot path. > > A storm at boot maybe.. or SCSI rescan but... > > I had it mixed up with the recent blk_max_size_offset() - you are right, > this is not in a hot path. For that case, I don't really care, it's fine. > > Is v2 runtime tested? Yes. Here is the DM stack for an lvm created dm-thin-pool (dm-5). # lsblk /dev/skd0 NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT skd0 252:0 0 745.3G 0 disk ├─bricks-mypool_tmeta 253:2 0 15.8G 0 lvm │ └─bricks-mypool-tpool 253:4 0 512G 0 lvm │ └─bricks-mypool 253:5 0 512G 0 lvm └─bricks-mypool_tdata 253:3 0 512G 0 lvm └─bricks-mypool-tpool 253:4 0 512G 0 lvm └─bricks-mypool 253:5 0 512G 0 lvm Before patch: # cat /sys/block/dm-5/alignment_offset 1048576 After patch: # cat /sys/block/dm-5/alignment_offset 0