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Subject: Re: [PATCH v2] powerpc/mm: move warning from resize_hpt_for_hotplug()
To:     Laurent Vivier <lvivier@redhat.com>, linux-kernel@vger.kernel.org
Cc:     Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev@lists.ozlabs.org,
        David Gibson <david@gibson.dropbear.id.au>
References: <20190308105413.4302-1-lvivier@redhat.com>
 <3db6b64d-02d3-8aa7-80ca-3e469ea743ff@c-s.fr>
 <1dfe1a2e-f6f9-2d5d-a38e-ba4517794bad@redhat.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <6f089371-29e6-6fa9-379d-76d3a87e2b8b@c-s.fr>
Date:   Wed, 13 Mar 2019 09:28:39 +0100
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Le 13/03/2019 à 09:01, Laurent Vivier a écrit :
> On 13/03/2019 07:03, Christophe Leroy wrote:
>>
>>
>> Le 08/03/2019 à 11:54, Laurent Vivier a écrit :
>>> resize_hpt_for_hotplug() reports a warning when it cannot
>>> resize the hash page table ("Unable to resize hash page
>>> table to target order") but in some cases it's not a problem
>>> and can make user thinks something has not worked properly.
>>>
>>> This patch moves the warning to arch_remove_memory() to
>>> only report the problem when it is needed.
>>>
>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>> ---
>>>    arch/powerpc/include/asm/sparsemem.h  |  4 ++--
>>>    arch/powerpc/mm/hash_utils_64.c       | 17 ++++++-----------
>>>    arch/powerpc/mm/mem.c                 |  3 ++-
>>>    arch/powerpc/platforms/pseries/lpar.c |  3 ++-
>>>    4 files changed, 12 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/sparsemem.h
>>> b/arch/powerpc/include/asm/sparsemem.h
>>> index 68da49320592..3192d454a733 100644
>>> --- a/arch/powerpc/include/asm/sparsemem.h
>>> +++ b/arch/powerpc/include/asm/sparsemem.h
>>> @@ -17,9 +17,9 @@ extern int create_section_mapping(unsigned long
>>> start, unsigned long end, int ni
>>>    extern int remove_section_mapping(unsigned long start, unsigned long
>>> end);
>>>      #ifdef CONFIG_PPC_BOOK3S_64
>>> -extern void resize_hpt_for_hotplug(unsigned long new_mem_size);
>>> +extern int resize_hpt_for_hotplug(unsigned long new_mem_size);
>>>    #else
>>> -static inline void resize_hpt_for_hotplug(unsigned long new_mem_size)
>>> { }
>>> +static inline int resize_hpt_for_hotplug(unsigned long new_mem_size)
>>> { return 0; }
>>>    #endif
>>>      #ifdef CONFIG_NUMA
>>> diff --git a/arch/powerpc/mm/hash_utils_64.c
>>> b/arch/powerpc/mm/hash_utils_64.c
>>> index 0cc7fbc3bd1c..40bb2a8326bb 100644
>>> --- a/arch/powerpc/mm/hash_utils_64.c
>>> +++ b/arch/powerpc/mm/hash_utils_64.c
>>> @@ -755,12 +755,12 @@ static unsigned long __init
>>> htab_get_table_size(void)
>>>    }
>>>      #ifdef CONFIG_MEMORY_HOTPLUG
>>> -void resize_hpt_for_hotplug(unsigned long new_mem_size)
>>> +int resize_hpt_for_hotplug(unsigned long new_mem_size)
>>>    {
>>>        unsigned target_hpt_shift;
>>>          if (!mmu_hash_ops.resize_hpt)
>>> -        return;
>>> +        return 0;
>>>          target_hpt_shift = htab_shift_for_mem_size(new_mem_size);
>>>    @@ -773,15 +773,10 @@ void resize_hpt_for_hotplug(unsigned long
>>> new_mem_size)
>>>         * current shift
>>>         */
>>>        if ((target_hpt_shift > ppc64_pft_size)
>>> -        || (target_hpt_shift < (ppc64_pft_size - 1))) {
>>> -        int rc;
>>> -
>>> -        rc = mmu_hash_ops.resize_hpt(target_hpt_shift);
>>> -        if (rc && (rc != -ENODEV))
>>> -            printk(KERN_WARNING
>>> -                   "Unable to resize hash page table to target order
>>> %d: %d\n",
>>> -                   target_hpt_shift, rc);
>>> -    }
>>> +        || (target_hpt_shift < (ppc64_pft_size - 1)))
>>
>> The || should go on the line above and the two (target_hpt... should be
>> aligned, and the () after the < are superflous.
>>
>> And indeed, we should (in another patch) rename 'target_hpt_shift' with
>> a shorter name, this would avoid multiple lines.
>>
>> Ref
>> https://www.kernel.org/doc/html/latest/process/coding-style.html#naming :
>>
>> LOCAL variable names should be short, and to the point. If you have some
>> random integer loop counter, it should probably be called i. Calling it
>> loop_counter is non-productive, if there is no chance of it being
>> mis-understood. Similarly, tmp can be just about any type of variable
>> that is used to hold a temporary value.
>>
>> If you are afraid to mix up your local variable names, you have another
>> problem, which is called the function-growth-hormone-imbalance syndrome.
>> See chapter 6 (Functions).
>>
> 
> I'm only removing a warning. Do we really need to rewrite all the code
> around for that?

No, and that's the reason why I said it could be done in another 
(future) patch.

Anyway, your patch should be clean regarding checkpatch

See https://patchwork.ozlabs.org/patch/1052984/
And 
https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/3298//artifact/linux/checkpatch.log

CHECK:AVOID_EXTERNS: extern prototypes should be avoided in .h files
#31: FILE: arch/powerpc/include/asm/sparsemem.h:20:
+extern int resize_hpt_for_hotplug(unsigned long new_mem_size);

CHECK:LOGICAL_CONTINUATIONS: Logical continuations should be on the 
previous line
#70: FILE: arch/powerpc/mm/hash_utils_64.c:776:
  	if ((target_hpt_shift > ppc64_pft_size)
+	    || (target_hpt_shift < (ppc64_pft_size - 1)))

total: 0 errors, 0 warnings, 2 checks, 60 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
       mechanically convert to the typical style using --fix or 
--fix-inplace.

the.patch has style problems, please review.

NOTE: Ignored message types: ARCH_INCLUDE_LINUX BIT_MACRO 
COMPARISON_TO_NULL DT_SPLIT_BINDING_PATCH EMAIL_SUBJECT 
FILE_PATH_CHANGES GLOBAL_INITIALISERS LINE_SPACING MULTIPLE_ASSIGNMENTS

NOTE: If any of the errors are false positives, please report
       them to the maintainer, see CHECKPATCH in MAINTAINERS.

Christophe

> 
> Thanks,
> Laurent
>