From: Dan Williams <dan.j.williams@intel.com>
To: "Kani, Toshi" <toshi.kani@hpe.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
"snitzer@redhat.com" <snitzer@redhat.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"ross.zwisler@linux.intel.com" <ross.zwisler@linux.intel.com>,
"dm-devel@redhat.com" <dm-devel@redhat.com>
Subject: Re: [PATCH v3 1/3] pmem: only set QUEUE_FLAG_DAX for fsdax mode
Date: Tue, 26 Jun 2018 14:51:52 -0700 [thread overview]
Message-ID: <CAPcyv4ifHX95fCM9Xj87CugwNWzgq=y-4LxPQ5L6RdjX0jdctQ@mail.gmail.com> (raw)
In-Reply-To: <1530048545.14039.288.camel@hpe.com>
On Tue, Jun 26, 2018 at 2:31 PM, Kani, Toshi <toshi.kani@hpe.com> wrote:
> On Tue, 2018-06-26 at 14:28 -0700, Dan Williams wrote:
>> On Tue, Jun 26, 2018 at 2:23 PM, Kani, Toshi <toshi.kani@hpe.com> wrote:
>> > On Tue, 2018-06-26 at 14:02 -0700, Dan Williams wrote:
>> > > On Tue, Jun 26, 2018 at 1:54 PM, Kani, Toshi <toshi.kani@hpe.com> wrote:
>>
>> [..]
>> > > > 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.
>> > >
>> > > Still DAX with raw mode never really worked any way. It was also
>> > > something that was broken from day one. So what happens to someone who
>> > > happened to avoid all the problems with page-less DAX and enabled
>> > > device-mapper on top? That failure mode detail needs to be added to
>> > > this changelog if we want to propose this for -stable.
>> >
>> > My point is that the behavior should be consistent between pmem and
>> > device-mapper. When -o dax succeeds on a pmem, then it should succeed
>> > on a device-mapper on top of that pmem.
>> >
>> > Has the drop of dax support from raw mode made to -stable back to the
>> > baseline accepted 545ed20e6df6? It will introduce inconsistency,
>> > otherwise.
>>
>> That commit, 569d0365f571 "dax: require 'struct page' by default for
>> filesystem dax", has not been tagged for -stable.
>
> Then, Fixes tag should be set to 569d0365f571 to keep the behavior
> consistent.
Sure, and the failure mode is...? I'm thinking the commit log should say:
"Starting with commit 569d0365f571 "dax: require 'struct page' by
default for filesystem dax", dax is no longer supported for page-less
configurations. However, device-mapper sees the QUEUE_FLAG_DAX still
being set and falsely assumes that DAX is enabled, this leads to
<insert user visible failure mode details here>"
next prev parent reply other threads:[~2018-06-26 21:51 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-26 17:59 [PATCH v3 0/3] Fix DM DAX handling Ross Zwisler
2018-06-26 17:59 ` [PATCH v3 1/3] pmem: only set QUEUE_FLAG_DAX for fsdax mode Ross Zwisler
2018-06-26 18:52 ` Dan Williams
2018-06-26 18:58 ` Mike Snitzer
2018-06-26 19:07 ` Dan Williams
2018-06-26 19:12 ` Ross Zwisler
2018-06-26 19:13 ` Mike Snitzer
2018-06-26 19:19 ` Dan Williams
2018-06-26 20:54 ` Kani, Toshi
2018-06-26 21:02 ` Dan Williams
2018-06-26 21:23 ` Kani, Toshi
2018-06-26 21:28 ` Dan Williams
2018-06-26 21:31 ` Kani, Toshi
2018-06-26 21:51 ` Dan Williams [this message]
2018-06-26 22:04 ` Ross Zwisler
2018-06-28 17:42 ` Kani, Toshi
2018-06-28 17:48 ` Mike Snitzer
2018-06-28 17:59 ` Dan Williams
2018-06-28 18:01 ` Kani, Toshi
2018-06-28 19:04 ` Ross Zwisler
2018-06-28 19:40 ` Kani, Toshi
2018-06-26 19:11 ` Ross Zwisler
2018-06-26 17:59 ` [PATCH v3 2/3] dax: bdev_dax_supported() check for QUEUE_FLAG_DAX Ross Zwisler
2018-06-26 17:59 ` [PATCH v3 3/3] dm: prevent DAX mounts if not supported Ross Zwisler
2018-06-26 18:17 ` Mike Snitzer
2018-06-26 19:01 ` [PATCH v4 " Ross Zwisler
2018-06-26 18:48 ` [PATCH v3 0/3] Fix DM DAX handling Mike Snitzer
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