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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [RFC PATCH 1/4] libnvdimm/namespace: Make namespace size validation arch dependent
Date: Mon, 18 Nov 2019 15:21:57 +0530	[thread overview]
Message-ID: <87o8x9h5qa.fsf@linux.ibm.com> (raw)
In-Reply-To: <CAPcyv4hroohsrXT1YHQB-L8ZFa2kUW+bKy03We4Mt7afeJgu3Q@mail.gmail.com>

Dan Williams <dan.j.williams@intel.com> writes:

> On Sat, Nov 16, 2019 at 4:15 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:
>>

....


>>
>> Considering the direct-map map size is not going to be user selectable,
>> do you agree that we can skip the above step 0 configuration you
>> suggested.
>>
>> The changes proposed in the patch series essentially does the rest.
>>
>> 1) It validate the size against the arch specific limit during
>> namespace creation. (part of step 1)
>
> This validation is a surprise failure to ndctl.
>
>> 2) It also disable initializing a region if it find the size not
>> correctly aligned as per the platform requirement.
>
> There needs to be a way for the user to discover the correct alignment
> that the kernel will accept.
>
>> 3) Direct map  mapping size is different from supported_alignment for a
>> namespace. The supported alignment controls what possible PAGE SIZE user want the
>> namespace to be mapped to user space.
>
> No, the namespace alignment is different than the page mapping size.
> The alignment is only interpreted as a mapping size at the device-dax
> level, otherwise at the raw namespace level it's just an arbitrary
> alignment.
>
>> With the above do you think the current patch series is good?
>
> I don't think we've quite converged on a solution.

How about we make it a property of seed device. ie,
we add `supported_size_align` RO attribute to the seed device. ndctl can
use this to validate the size value. So this now becomes step0

sys/bus/nd/devices/region0> cat btt0.0/supported_size_align 
16777216
/sys/bus/nd/devices/region0> cat pfn0.0/supported_size_align 
16777216
/sys/bus/nd/devices/region0> cat dax0.0/supported_size_align 
16777216
/sys/bus/nd/devices/region0>

We follow that up with validating the size value written to size
attribute(step 1).

While initializing the namespaces already present in a region we again
validate the size and if not properly aligned we mark the region
disabled.

-aneesh

  reply	other threads:[~2019-11-18  9:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28  9:48 [RFC PATCH 1/4] libnvdimm/namespace: Make namespace size validation arch dependent Aneesh Kumar K.V
2019-10-28  9:48 ` [RFC PATCH 2/4] libnvdimm/namespace: Disable the region if the namespace size is not aligned correctly Aneesh Kumar K.V
2019-10-28  9:48 ` [RFC PATCH 3/4] libnvdimm/namespace: Use direct-mapping page size to validate namespace size Aneesh Kumar K.V
2019-10-28  9:48 ` [RFC PATCH 4/4] libnvdimm/namespace: Add debug check while initializing namespace resource size Aneesh Kumar K.V
2019-10-28 21:21 ` [RFC PATCH 1/4] libnvdimm/namespace: Make namespace size validation arch dependent Ira Weiny
2019-10-29  4:34   ` Aneesh Kumar K.V
2019-10-28 23:08 ` Dan Williams
2019-10-29  4:34   ` Aneesh Kumar K.V
2019-10-29  5:30     ` Dan Williams
2019-10-31  5:35       ` Aneesh Kumar K.V
2019-10-31  6:30         ` Dan Williams
2019-10-31  8:37           ` Aneesh Kumar K.V
2019-10-31 15:53             ` Dan Williams
2019-11-06 10:44           ` Aneesh Kumar K.V
2019-11-16 12:15             ` Aneesh Kumar K.V
2019-11-16 18:50               ` Dan Williams
2019-11-18  9:51                 ` Aneesh Kumar K.V [this message]
2019-11-19 17:58                   ` Dan Williams
2019-11-20  3:19                     ` Aneesh Kumar K.V
2019-11-20  3:46                       ` Dan Williams

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