From: "Kani, Toshimitsu" <toshi.kani@hpe.com> To: "dan.j.williams@intel.com" <dan.j.williams@intel.com> Cc: "x86@kernel.org" <x86@kernel.org>, "jack@suse.cz" <jack@suse.cz>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, "mawilcox@microsoft.com" <mawilcox@microsoft.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "hch@lst.de" <hch@lst.de> Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges Date: Thu, 6 Jul 2017 01:17:45 +0000 [thread overview] Message-ID: <1499303324.2042.7.camel@hpe.com> (raw) In-Reply-To: <CAPcyv4ixQFNT_8tGFyf2ABqxpPd-jmtXKVeLBRdzBW12u3TJbg@mail.gmail.com> On Wed, 2017-07-05 at 17:07 -0700, Dan Williams wrote: > On Wed, Jul 5, 2017 at 4:46 PM, Kani, Toshimitsu <toshi.kani@hpe.com> > wrote: > > On Thu, 2017-06-29 at 18:28 -0700, Dan Williams wrote: : > > > > Sorry for being late to respond, but I agree with Linda that this > > naming policy is likely to confuse users. I also care less about > > the current users who use memmap option. This case is pmem- > > emulation and they know what they are doing. > > > > Assuming block device interface is needed (in addition to device- > > dax) for volatile range for use-cases like swap device, I wonder if > > user can actually specify a right pmem device for swap from OS- > > install GUI when both volatile and persistent block devices are > > listed as /dev/pmemN. Sometimes we are restricted with GUI > > menu. Some users use GUI all the time like Windows as well. > > > > Can we differentiate the naming by adding 'v' like 'pmemNv' (if you > > can't go with 'vmemN')? I don't think having 's' for BTT was that > > bad. It's been helpful to tell users that these pmem devices are > > not byte-addressable. I also think that BTT for volatile range > > makes no sense (unless emulated as persistent memory by memmap > > option). > > I'm more worried about sending the wrong signal the other way. That > users believe that the 'p' means definitely "persistent" when we have > no way to guarantee that. That's a valid point. But isn't it vendors' responsibility to guarantee it when their devices are described as persistent in one way or the other in FW? > If it was only memmap= that we had to worry about that would be one > thing, but we apparently have vendors that are shipping "e820-type-12 > memory" as their NVDIMM solution [1]. Type-12 is persistent memory in a non-standard FW interface. So, it makes sense to show it as pmem. > We've also been shipping the policy that 'pmem' may front a volatile > range ever since v4.8 (commit c2f32acdf848 "acpi, nfit: treat virtual > ramdisk SPA as pmem region"). At least now we have the "nd_volatile" > region type. Any change of the device name now is potentially a > regression for environments that are already expecting /dev/pmemX. Hmm... I thought this was for mapping ISO image for booting. Does it get listed as a regular pmem device and allow user to modify its content? I doubt this case being used today, though. (It was prototyped on an HPE box and I can check the status if needed.) > As far as I know there are no OS installers that understand pmem. It's actually the other way around. It was changed not to list pmem devices since OS cannot boot from a pmem yet... > When they do add support I think it would be straightforward to avoid > confusion and filter "volatile" hosted pmem devices from the install > target list. I don't see this being much different from the confusion > when users can not differentiate their 'sd' device between USB and > SATA. Right, such changes can be made. It was just an example that typical use-cases today do not require additional step to check persistence of block devices. > We have symlinks in /dev/disk/by* to make it easier to identify > storage devices, I think it makes sense to add udev rules for > identifying volatile pmem and not try to differentiate this in the > default kernel device name. I am not sure what might be a good way, but I am concerned because a single block device naming do not represent both volatile and persistent media today. Thanks, -Toshi _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: "Kani, Toshimitsu" <toshi.kani@hpe.com> To: "dan.j.williams@intel.com" <dan.j.williams@intel.com> Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "hch@lst.de" <hch@lst.de>, "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "x86@kernel.org" <x86@kernel.org>, "mawilcox@microsoft.com" <mawilcox@microsoft.com>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, "Knippers, Linda" <linda.knippers@hpe.com>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, "jack@suse.cz" <jack@suse.cz> Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges Date: Thu, 6 Jul 2017 01:17:45 +0000 [thread overview] Message-ID: <1499303324.2042.7.camel@hpe.com> (raw) In-Reply-To: <CAPcyv4ixQFNT_8tGFyf2ABqxpPd-jmtXKVeLBRdzBW12u3TJbg@mail.gmail.com> On Wed, 2017-07-05 at 17:07 -0700, Dan Williams wrote: > On Wed, Jul 5, 2017 at 4:46 PM, Kani, Toshimitsu <toshi.kani@hpe.com> > wrote: > > On Thu, 2017-06-29 at 18:28 -0700, Dan Williams wrote: : > > > > Sorry for being late to respond, but I agree with Linda that this > > naming policy is likely to confuse users. I also care less about > > the current users who use memmap option. This case is pmem- > > emulation and they know what they are doing. > > > > Assuming block device interface is needed (in addition to device- > > dax) for volatile range for use-cases like swap device, I wonder if > > user can actually specify a right pmem device for swap from OS- > > install GUI when both volatile and persistent block devices are > > listed as /dev/pmemN. Sometimes we are restricted with GUI > > menu. Some users use GUI all the time like Windows as well. > > > > Can we differentiate the naming by adding 'v' like 'pmemNv' (if you > > can't go with 'vmemN')? I don't think having 's' for BTT was that > > bad. It's been helpful to tell users that these pmem devices are > > not byte-addressable. I also think that BTT for volatile range > > makes no sense (unless emulated as persistent memory by memmap > > option). > > I'm more worried about sending the wrong signal the other way. That > users believe that the 'p' means definitely "persistent" when we have > no way to guarantee that. That's a valid point. But isn't it vendors' responsibility to guarantee it when their devices are described as persistent in one way or the other in FW? > If it was only memmap= that we had to worry about that would be one > thing, but we apparently have vendors that are shipping "e820-type-12 > memory" as their NVDIMM solution [1]. Type-12 is persistent memory in a non-standard FW interface. So, it makes sense to show it as pmem. > We've also been shipping the policy that 'pmem' may front a volatile > range ever since v4.8 (commit c2f32acdf848 "acpi, nfit: treat virtual > ramdisk SPA as pmem region"). At least now we have the "nd_volatile" > region type. Any change of the device name now is potentially a > regression for environments that are already expecting /dev/pmemX. Hmm... I thought this was for mapping ISO image for booting. Does it get listed as a regular pmem device and allow user to modify its content? I doubt this case being used today, though. (It was prototyped on an HPE box and I can check the status if needed.) > As far as I know there are no OS installers that understand pmem. It's actually the other way around. It was changed not to list pmem devices since OS cannot boot from a pmem yet... > When they do add support I think it would be straightforward to avoid > confusion and filter "volatile" hosted pmem devices from the install > target list. I don't see this being much different from the confusion > when users can not differentiate their 'sd' device between USB and > SATA. Right, such changes can be made. It was just an example that typical use-cases today do not require additional step to check persistence of block devices. > We have symlinks in /dev/disk/by* to make it easier to identify > storage devices, I think it makes sense to add udev rules for > identifying volatile pmem and not try to differentiate this in the > default kernel device name. I am not sure what might be a good way, but I am concerned because a single block device naming do not represent both volatile and persistent media today. Thanks, -Toshi
next prev parent reply other threads:[~2017-07-06 1:17 UTC|newest] Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-06-29 17:52 [PATCH v4 00/16] pmem: stop abusing copy_user_nocache(), and other reworks Dan Williams 2017-06-29 17:52 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 01/16] x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 02/16] dm: add ->copy_from_iter() dax operation support Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 03/16] filesystem-dax: convert to dax_copy_from_iter() Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 04/16] dax, pmem: introduce an optional 'flush' dax_operation Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 05/16] dm: add ->flush() dax operation support Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 06/16] filesystem-dax: convert to dax_flush() Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 07/16] x86, dax: replace clear_pmem() with open coded memset + dax_ops->flush Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 08/16] x86, dax, libnvdimm: remove wb_cache_pmem() indirection Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 09/16] x86, libnvdimm, pmem: move arch_invalidate_pmem() to libnvdimm Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 10/16] x86, libnvdimm, pmem: remove global pmem api Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:53 ` [PATCH v4 11/16] libnvdimm, pmem: fix persistence warning Dan Williams 2017-06-29 17:53 ` Dan Williams 2017-06-29 17:54 ` [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges Dan Williams 2017-06-29 17:54 ` Dan Williams 2017-06-29 19:20 ` Linda Knippers 2017-06-29 19:20 ` Linda Knippers 2017-06-29 20:42 ` Dan Williams 2017-06-29 20:42 ` Dan Williams 2017-06-29 21:16 ` Linda Knippers 2017-06-29 21:16 ` Linda Knippers 2017-06-29 21:50 ` Dan Williams 2017-06-29 21:50 ` Dan Williams 2017-06-29 22:12 ` Linda Knippers 2017-06-29 22:12 ` Linda Knippers 2017-06-29 22:28 ` Dan Williams 2017-06-29 22:28 ` Dan Williams 2017-06-29 22:35 ` Linda Knippers 2017-06-29 22:35 ` Linda Knippers 2017-06-29 22:43 ` Dan Williams 2017-06-29 22:43 ` Dan Williams 2017-06-29 22:49 ` Linda Knippers 2017-06-29 22:49 ` Linda Knippers 2017-06-29 22:58 ` Dan Williams 2017-06-29 22:58 ` Dan Williams 2017-06-29 23:14 ` Linda Knippers 2017-06-29 23:14 ` Linda Knippers 2017-06-30 1:28 ` Dan Williams 2017-06-30 1:28 ` Dan Williams 2017-07-05 23:46 ` Kani, Toshimitsu 2017-07-05 23:46 ` Kani, Toshimitsu 2017-07-06 0:07 ` Dan Williams 2017-07-06 0:07 ` Dan Williams 2017-07-06 1:17 ` Kani, Toshimitsu [this message] 2017-07-06 1:17 ` Kani, Toshimitsu 2017-07-06 2:08 ` Dan Williams 2017-07-06 2:08 ` Dan Williams 2017-07-06 2:11 ` hch 2017-07-06 2:11 ` hch 2017-07-06 2:53 ` Oliver 2017-07-06 2:53 ` Oliver 2017-07-06 2:56 ` hch 2017-07-06 2:56 ` hch 2017-06-29 17:54 ` [PATCH v4 13/16] dax: remove default copy_from_iter fallback Dan Williams 2017-06-29 17:54 ` Dan Williams 2017-06-29 17:54 ` [PATCH v4 14/16] dax: convert to bitmask for flags Dan Williams 2017-06-29 17:54 ` Dan Williams 2017-06-29 17:54 ` [PATCH v4 15/16] libnvdimm, pmem, dax: export a cache control attribute Dan Williams 2017-06-29 17:54 ` Dan Williams 2017-06-29 17:54 ` [PATCH v4 16/16] libnvdimm, pmem: disable dax flushing when pmem is fronting a volatile region Dan Williams 2017-06-29 17:54 ` Dan Williams
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