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Date: Wed, 29 Jun 2022 08:00:27 +0700
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To: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Cc: Jens Axboe <axboe@kernel.dk>, Fernanda Ma'rouf
 <fernandafmr12@gnuweeb.org>, Pavel Begunkov <asml.silence@gmail.com>,
 Hao Xu <howeyxu@tencent.com>,
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References: <20220629002028.1232579-1-ammar.faizi@intel.com>
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From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Subject: Re: [PATCH liburing v1 2/9] setup: Handle `get_page_size()` failure
 (for aarch64 nolibc support)
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On 6/29/22 7:50 AM, Alviro Iskandar Setiawan wrote:
> On Wed, Jun 29, 2022 at 7:28 AM Ammar Faizi wrote:
>>          page_size = get_page_size();
>> +       if (page_size < 0)
>> +               return page_size;
>> +
>>          return rings_size(p, entries, cq_entries, page_size);
>>   }
> 
> the current error handling fallback to 4K if fail on sysconf(_SC_PAGESIZE):
> https://github.com/axboe/liburing/blob/68103b731c34a9f83c181cb33eb424f46f3dcb94/src/arch/generic/lib.h#L10-L19
> with this patch, get_page_size() is only possible to return negative
> value on aarch64.

Ah right, this one needs a revision. Either we fallback to 4K, or
return error if we fail.

> i don't understand why the current master branch code fallback to 4K when fail?

Neither do I. Maybe because 4K is widely used page size?

Jens, can you shed some light on this?

   The current upstream does this:

      - For x86/x86-64, it's hard-coded to 4K. So it can't fail.
      - For other archs, if sysconf(_SC_PAGESIZE) fails, we fallback to 4K.

Now we are going to add aarch64, it uses a group of syscalls to get the page
size. So it may fail. What should we do when we fail?

Fallback to 4K? Or return error code from syscall?
       
-- 
Ammar Faizi