Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value

From	David Rientjes <rientjes@google.com>
Newsgroups	linux.kernel
Subject	Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value
Date	2016-09-01 02:30 +0200
Message-ID	<sco3f-Yp-1@gated-at.bofh.it> (permalink)
References	(2 earlier) <sckiZ-74j-27@gated-at.bofh.it> <sckVJ-7wC-35@gated-at.bofh.it> <scngR-sq-3@gated-at.bofh.it> <scnJT-Ri-3@gated-at.bofh.it> <scnTz-UF-1@gated-at.bofh.it>
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On Wed, 31 Aug 2016, Reza Arbab wrote:

> > Nope, the return value of changing state from online to online was
> > established almost 11 years ago in commit 3947be1969a9.
> 
> Fair enough. So if online-to-online is -EINVAL, 

online-to-online for state is -EINVAL, it has been since 2005.

> 1. Shouldn't 'echo 1 > online' then also return -EINVAL?
> 

No, it's a different tunable.  There's no requirement that two different 
tunables that do a similar thing have the same return values: the former 
existed long before device_online() and still exists for backwards 
compatibility.

> 2. store_mem_state() still needs a tweak, right? It was only returning -EINVAL
> by accident, due to the convoluted sequence I listed in the patch.
> 

Yes, absolutely.  It returning -EINVAL for "nline" is what is accidently 
preserving it's backwards compatibility :)  Note that device_online() 
returns 1 if already online and memory_subsys_online() returns 0 if online 
in this case.  So we want store_mem_state() to return -EINVAL if 
device_online() returns non-zero (this was in my first email).

Thread

Re: [PATCH v2] memory-hotplug: fix store_mem_state() return value Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-31 14:30 +0200
  Re: [PATCH v2] memory-hotplug: fix store_mem_state() return value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-08-31 16:40 +0200
    Re: [PATCH v2] memory-hotplug: fix store_mem_state() return value Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-31 17:10 +0200
      [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-08-31 17:50 +0200
        Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value Andrew Morton <akpm@linux-foundation.org> - 2016-08-31 22:30 +0200
          Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value David Rientjes <rientjes@google.com> - 2016-08-31 23:10 +0200
            Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-09-01 01:40 +0200
              Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value David Rientjes <rientjes@google.com> - 2016-09-01 02:10 +0200
                Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-09-01 02:20 +0200
                Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value David Rientjes <rientjes@google.com> - 2016-09-01 02:30 +0200
                Re: [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return  value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-09-01 04:00 +0200
  [RESEND PATCH v2] memory-hotplug: fix store_mem_state() return value Reza Arbab <arbab@linux.vnet.ibm.com> - 2016-08-31 16:40 +0200

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