From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kani, Toshi" Subject: Re: [PATCH v3 1/3] pmem: only set QUEUE_FLAG_DAX for fsdax mode Date: Tue, 26 Jun 2018 20:54:03 +0000 Message-ID: <1530046327.14039.273.camel@hpe.com> References: <20180626175932.8899-1-ross.zwisler@linux.intel.com> <20180626175932.8899-2-ross.zwisler@linux.intel.com> <20180626185830.GA7171@redhat.com> <20180626191346.GA7233@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180626191346.GA7233-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Content-ID: <3D1889CB4901114A9FD8D1212F7DAD23-mmYPd6ayCNGroOM5E8FhRbjFIynDaujOfM0AETQt39g@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: "dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" Cc: "linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: dm-devel.ids On Tue, 2018-06-26 at 15:13 -0400, Mike Snitzer wrote: > On Tue, Jun 26 2018 at 3:07pm -0400, > Dan Williams wrote: > > > On Tue, Jun 26, 2018 at 11:58 AM, Mike Snitzer wrote: > > > On Tue, Jun 26 2018 at 2:52pm -0400, > > > Dan Williams wrote: > > > > > > > On Tue, Jun 26, 2018 at 10:59 AM, Ross Zwisler > > > > wrote: > > > > > QUEUE_FLAG_DAX is an indication that a given block device supports > > > > > filesystem DAX and should not be set for PMEM namespaces which are in "raw" > > > > > or "sector" modes. These namespaces lack struct page and are prevented > > > > > from participating in filesystem DAX. > > > > > > > > > > Signed-off-by: Ross Zwisler > > > > > Suggested-by: Mike Snitzer > > > > > Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > > > > > > > Why is this cc: stable? What is the user visible impact of this change > > > > especially given the requirement to validate QUEUE_FLAG_DAX with > > > > bdev_dax_supported()? Patch looks good, but it's just a cosmetic fixup > > > > afaics. > > > > > > This isn't cosmetic when you consider that stacking up a DM device is > > > looking at this flag to determine whether a table does or does _not_ > > > support DAX. > > > > > > So this patch, in conjunction with the other changes in the series, is > > > certainly something I'd consider appropriate for stable. > > > > I think this classifies as something that never worked correctly and > > is not a regression. It does not identify which commit it is repairing > > or the user visible failure mode. > > So you're taking issue with making stacked dax configs work in older > kernels? That's fine. We can drop the stable cc if you like. > > But I mean we intended for this to work.. so the Fixes commit references > can easily be added, e.g.: 545ed20e6df68a4d2584a29a2a28ee8b2f7e9547 > ("dm: add infrastructure for DAX support") When this dm change was made, the pmem driver supported DAX for both raw and memory modes (note: sector mode does not use the pmem driver). I think the issue was introduced when we dropped DAX support from raw mode. Thanks, -Toshi