Date:   Thu, 16 Mar 2023 11:18:25 -0400
From:   Peter Xu <peterx@redhat.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Yang Shi <shy828301@gmail.com>
Subject: Re: [PATCH] mm/thp: Rename TRANSPARENT_HUGEPAGE_NEVER_DAX to
 _UNSUPPORTED
Message-ID: <ZBMzQW674oHQJV7F@x1n>
References: <20230315171642.1244625-1-peterx@redhat.com>
 <83625129-26c9-8885-7367-bb56bc5367f3@redhat.com>
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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@linux.ibm.com>
> > Cc: Yang Shi <shy828301@gmail.com>
> > Signed-off-by: Peter Xu <peterx@redhat.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.

-- 
Peter Xu

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From 0d01260fedfd9d99c1eeac10f9bddd52477823bd Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Thu, 16 Mar 2023 11:08:47 -0400
Subject: [PATCH] fixup! mm/thp: rename TRANSPARENT_HUGEPAGE_NEVER_DAX to
 _UNSUPPORTED

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 mm/huge_memory.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2bb16cf4cafa..81a5689806af 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -460,10 +460,6 @@ static int __init hugepage_init(void)
 	struct kobject *hugepage_kobj;
 
 	if (!has_transparent_hugepage()) {
-		/*
-		 * Hardware doesn't support hugepages, hence disable
-		 * DAX PMD support.
-		 */
 		transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
 		return -EINVAL;
 	}
-- 
2.39.1


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