Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753978AbaFJVVW (ORCPT ); Tue, 10 Jun 2014 17:21:22 -0400 Received: from mga02.intel.com ([134.134.136.20]:41808 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753839AbaFJVVU (ORCPT ); Tue, 10 Jun 2014 17:21:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,1011,1392192000"; d="scan'208";a="555349760" Date: Tue, 10 Jun 2014 15:21:18 -0600 (MDT) From: Keith Busch X-X-Sender: vmware@localhost.localdom To: Jens Axboe cc: Keith Busch , =?ISO-8859-15?Q?Matias_Bj=F8rling?= , "willy@linux.intel.com" , "sbradshaw@micron.com" , "tom.leiming@gmail.com" , "hch@infradead.org" , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH v7] NVMe: conversion to blk-mq In-Reply-To: <5397753B.2020009@fb.com> Message-ID: References: <1402392038-5268-1-git-send-email-m@bjorling.me> <1402392038-5268-2-git-send-email-m@bjorling.me>, <5397636F.9050209@fb.com> <5397753B.2020009@fb.com> User-Agent: Alpine 2.03 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Jun 2014, Jens Axboe wrote: > On 06/10/2014 03:10 PM, Keith Busch wrote: >> On Tue, 10 Jun 2014, Jens Axboe wrote: >>> On 06/10/2014 01:29 PM, Keith Busch wrote: >>>> I have two devices, one formatted 4k, the other 512. The 4k is used as >>>> the TEST_DEV and 512 is used as SCRATCH_DEV. I'm always hitting a BUG >>>> when >>>> unmounting the scratch dev in xfstests generic/068. The bug looks like >>>> nvme was trying to use an SGL that doesn't map correctly to a PRP. >>> >>> I'm guessing it's some of the coalescing settings, since the driver is >>> now using the generic block rq mapping. >> >> Ok, sounds right. I mentioned in a way earlier review it doesn't look >> like a request that doesn't conform to a PRP list would get split anymore, >> and this test seems to confirm that. >> >> Can we create something that will allow a driver to add DMA constraints to >> a request queue with the rules of a PRP list? > > I haven't even looked at the rules - can you briefly outline them? From > a quick look, seems it does prp chaining for every 512 entries. But > nvme_setup_prps() looks like voodoo to an uninitiated, it could have > used a comment or two :-) Yeah, nvme_setup_prps is probably the least readable code in this driver. Maybe some comments are in order here... There are two rules for an SGL to be mappable to a PRP: 1. Every element must have zero page offset, except the first. 2. Every element must end on a page boundary, except the last. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/