linux-kernel - Re: [PATCH] mm/thp: Rename TRANSPARENT_HUGEPAGE_NEVER_DAX to

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Message-ID: <e25eca2e-67c8-bcd5-69f8-f6590fc0b011@redhat.com>
Date:   Thu, 16 Mar 2023 16:37:36 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>
Subject: Re: [PATCH] mm/thp: Rename TRANSPARENT_HUGEPAGE_NEVER_DAX to
 _UNSUPPORTED

On 16.03.23 16:18, Peter Xu wrote:
> On Thu, Mar 16, 2023 at 03:57:12PM +0100, David Hildenbrand wrote:
>> On 15.03.23 18:16, Peter Xu wrote:
>>> TRANSPARENT_HUGEPAGE_NEVER_DAX has nothing to do with DAX.  It's set when
>>> has_transparent_hugepage() returns false, checked in hugepage_vma_check()
>>> and will disable THP completely if false.  Rename it to reflect its real
>>> purpose.
>>>
>>> Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
>>> Cc: Yang Shi <shy828301@...il.com>
>>> Signed-off-by: Peter Xu <peterx@...hat.com>
>>> ---
>>>    include/linux/huge_mm.h | 2 +-
>>>    mm/huge_memory.c        | 4 ++--
>>>    2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>>> index 70bd867eba94..9a3a3af2dd80 100644
>>> --- a/include/linux/huge_mm.h
>>> +++ b/include/linux/huge_mm.h
>>> @@ -79,7 +79,7 @@ static inline vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn,
>>>    }
>>>    enum transparent_hugepage_flag {
>>> -	TRANSPARENT_HUGEPAGE_NEVER_DAX,
>>> +	TRANSPARENT_HUGEPAGE_UNSUPPORTED,
>>>    	TRANSPARENT_HUGEPAGE_FLAG,
>>>    	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
>>>    	TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index b0ab247939e0..913e7dc32869 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -88,7 +88,7 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
>>>    	/*
>>>    	 * If the hardware/firmware marked hugepage support disabled.
>>>    	 */
>>> -	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX))
>>> +	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
>>>    		return false;
>>>    	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
>>> @@ -464,7 +464,7 @@ static int __init hugepage_init(void)
>>>    		 * Hardware doesn't support hugepages, hence disable
>>>    		 * DAX PMD support.
>>
>>
>> We should also fixup that comment then, no?
> 
> Yes, I'd drop the comment since the code explains itself.  One fixup
> attached.  Thanks.

LGTM

-- 
Thanks,

David / dhildenb