From mboxrd@z Thu Jan 1 00:00:00 1970 From: axboe@fb.com (Jens Axboe) Date: Tue, 10 Jun 2014 15:14:35 -0600 Subject: [PATCH v7] NVMe: conversion to blk-mq In-Reply-To: References: <1402392038-5268-1-git-send-email-m@bjorling.me> <1402392038-5268-2-git-send-email-m@bjorling.me>, <5397636F.9050209@fb.com> Message-ID: <5397753B.2020009@fb.com> 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 :-)