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SubjectRe: [PATCHSETS] v14 fsdax-rmap + v11 fsdax-reflink
From
Hi,

Is there any other work I should do with these two patchsets? I think
they are good for now. So... since the 5.19-rc1 is coming, could the
notify_failure() part be merged as your plan?


--
Thanks,
Ruan.


在 2022/5/12 20:27, Shiyang Ruan 写道:
>
>
> 在 2022/5/11 23:46, Dan Williams 写道:
>> On Wed, May 11, 2022 at 8:21 AM Darrick J. Wong <djwong@kernel.org>
>> wrote:
>>>
>>> Oan Tue, May 10, 2022 at 10:24:28PM -0700, Andrew Morton wrote:
>>>> On Tue, 10 May 2022 19:43:01 -0700 "Darrick J. Wong"
>>>> <djwong@kernel.org> wrote:
>>>>
>>>>> On Tue, May 10, 2022 at 07:28:53PM -0700, Andrew Morton wrote:
>>>>>> On Tue, 10 May 2022 18:55:50 -0700 Dan Williams
>>>>>> <dan.j.williams@intel.com> wrote:
>>>>>>
>>>>>>>> It'll need to be a stable branch somewhere, but I don't think it
>>>>>>>> really matters where al long as it's merged into the xfs for-next
>>>>>>>> tree so it gets filesystem test coverage...
>>>>>>>
>>>>>>> So how about let the notify_failure() bits go through -mm this
>>>>>>> cycle,
>>>>>>> if Andrew will have it, and then the reflnk work has a clean
>>>>>>> v5.19-rc1
>>>>>>> baseline to build from?
>>>>>>
>>>>>> What are we referring to here?  I think a minimal thing would be the
>>>>>> memremap.h and memory-failure.c changes from
>>>>>> https://lkml.kernel.org/r/20220508143620.1775214-4-ruansy.fnst@fujitsu.com
>>>>>> ?
>>>>>>
>>>>>> Sure, I can scoot that into 5.19-rc1 if you think that's best.  It
>>>>>> would probably be straining things to slip it into 5.19.
>>>>>>
>>>>>> The use of EOPNOTSUPP is a bit suspect, btw.  It *sounds* like the
>>>>>> right thing, but it's a networking errno.  I suppose livable with
>>>>>> if it
>>>>>> never escapes the kernel, but if it can get back to userspace then a
>>>>>> user would be justified in wondering how the heck a filesystem
>>>>>> operation generated a networking errno?
>>>>>
>>>>> <shrug> most filesystems return EOPNOTSUPP rather enthusiastically
>>>>> when
>>>>> they don't know how to do something...
>>>>
>>>> Can it propagate back to userspace?
>>>
>>> AFAICT, the new code falls back to the current (mf_generic_kill_procs)
>>> failure code if the filesystem doesn't provide a ->memory_failure
>>> function or if it returns -EOPNOSUPP.  mf_generic_kill_procs can also
>>> return -EOPNOTSUPP, but all the memory_failure() callers (madvise, etc.)
>>> convert that to 0 before returning it to userspace.
>>>
>>> I suppose the weirder question is going to be what happens when madvise
>>> starts returning filesystem errors like EIO or EFSCORRUPTED when pmem
>>> loses half its brains and even the fs can't deal with it.
>>
>> Even then that notification is not in a system call context so it
>> would still result in a SIGBUS notification not a EOPNOTSUPP return
>> code. The only potential gap I see are what are the possible error
>> codes that MADV_SOFT_OFFLINE might see? The man page is silent on soft
>> offline failure codes. Shiyang, that's something to check / update if
>> necessary.
>
> According to the code around MADV_SOFT_OFFLINE, it will return -EIO when
> the backend is NVDIMM.
>
> Here is the logic:
>  madvise_inject_error() {
>      ...
>      if (MADV_SOFT_OFFLINE) {
>          ret = soft_offline_page() {
>              ...
>              /* Only online pages can be soft-offlined (esp., not
> ZONE_DEVICE). */
>              page = pfn_to_online_page(pfn);
>              if (!page) {
>                  put_ref_page(ref_page);
>                  return -EIO;
>              }
>              ...
>          }
>      } else {
>          ret = memory_failure()
>      }
>      return ret
>  }
>
>
> --
> Thanks,
> Ruan.
>
>


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