From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: SCSI bug Date: Sun, 21 Feb 2016 11:07:56 -0800 Message-ID: <1456081676.2340.10.camel@HansenPartnership.com> References: <28D5FC66-A9E6-4F3E-A8AC-F9E68A6BC543@bell.net> <82D4BF6F-05CF-4441-9530-79475BFF84F3@bell.net> <56C8E1AC.3030409@gmx.de> <038473FE-9E6D-4F03-BBD4-9844B7B529E1@bell.net> <9C42B388-96D5-412A-BAC3-14E93415CA21@bell.net> <1456026424.2268.5.camel@HansenPartnership.com> <14EF1F4E-8045-4990-B29E-D489E82B1929@bell.net> <1456078381.2340.5.camel@HansenPartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Helge Deller , linux-parisc List To: John David Anglin Return-path: In-Reply-To: List-ID: List-Id: linux-parisc.vger.kernel.org On Sun, 2016-02-21 at 13:43 -0500, John David Anglin wrote: > I verified that commit 54efd50bfd873e2dbf784e0b21a8027ba4299a3e in > linux-block fails to > boot and commit 41609892701e26724b8617201f43254cadf2e7ae (blk-cgroup: > Drop unlikely > before IS_ERR(_OR_NULL)) does boot successfully. Commit > 41609892701e26724b8617201f43254cadf2e7ae > is previous commit in tree. > > I don't believe that the change can be reverted from Linus' tree as > this commit allowed other > stuff to be removed (see second paragraph of commit description). OK, can you just verify you can boot 4.5-rc5 without the sata_sil24 driver? My theory, based on what Helge produced is that this commit is building a large transfer list > 65535 and then splitting it wrongly. I think the problem is that it's not respecting the DMA boundary, so Helge sees a transfer size of 69632 which I think slops over on both sides, requiring 3 segments to describe. However, the merge code thinks we only need two (because the length is < 2*65536). The reason we only see this with ATA drivers is because virtually no SCSI drivers set the DMA boundary. Most ATA drivers require a dma boundary of 65535. James