[PATCH V5 0/3] THP related cleanups

[PATCH V5 0/3] THP related cleanups

[Aneesh Kumar K.V]

Changes from V4:
* Folded patches in -mm
  mm-thp-split-out-pmd-collpase-flush-into-a-separate-functions-fix.patch
  mm-thp-split-out-pmd-collpase-flush-into-a-separate-functions-fix-2.patch
  mm-clarify-that-the-function-operateds-on-hugepage-pte-fix.patch
* Fix VM_BUG_ON on x86.
 the default implementation of pmdp_collapse_flush used the hugepage variant
 and hence can be called on pmd_t pointing to pgtable. This resulting in us
 hitting VM_BUG_ON in pmdp_clear_flush. Update powerpc/mm: Use generic version of pmdp_clear_flush
 to handle this.


NOTE: Can we get this tested on s390 ?

Aneesh Kumar K.V (3):
  mm/thp: Split out pmd collpase flush into a separate functions
  powerpc/mm: Use generic version of pmdp_clear_flush
  mm: Clarify that the function operates on hugepage pte

 arch/mips/include/asm/pgtable.h          |  8 ++--
 arch/powerpc/include/asm/pgtable-ppc64.h | 14 +++---
 arch/powerpc/mm/pgtable_64.c             | 73 +++++++++++++++-----------------
 arch/s390/include/asm/pgtable.h          | 30 ++++++++-----
 arch/sparc/include/asm/pgtable_64.h      |  8 ++--
 arch/tile/include/asm/pgtable.h          |  8 ++--
 arch/x86/include/asm/pgtable.h           |  4 +-
 include/asm-generic/pgtable.h            | 49 +++++++++++++++++----
 include/linux/mmu_notifier.h             | 12 +++---
 mm/huge_memory.c                         | 18 ++++----
 mm/migrate.c                             |  2 +-
 mm/pgtable-generic.c                     |  9 ++--
 mm/rmap.c                                |  2 +-
 13 files changed, 136 insertions(+), 101 deletions(-)

-- 
2.1.4

[PATCH V5 1/3] mm/thp: Split out pmd collpase flush into a separate functions

[Aneesh Kumar K.V]

Architectures like ppc64 [1] need to do special things while clearing
pmd before a collapse. For them this operation is largely different
from a normal hugepage pte clear. Hence add a separate function
to clear pmd before collapse. After this patch pmdp_* functions
operate only on hugepage pte, and not on regular pmd_t values
pointing to page table.

[1] ppc64 needs to invalidate all the normal page pte mappings we
already have inserted in the hardware hash page table. But before
doing that we need to make sure there are no parallel hash page
table insert going on. So we need to do a kick_all_cpus_sync()
before flushing the older hash table entries. By moving this to
a separate function we capture these details and mention how it
is different from a hugepage pte clear.

This patch is a cleanup and only does code movement for clarity.
There should not be any change in functionality.

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pgtable-ppc64.h |  4 ++
 arch/powerpc/mm/pgtable_64.c             | 76 +++++++++++++++++---------------
 include/asm-generic/pgtable.h            | 22 +++++++++
 mm/huge_memory.c                         |  2 +-
 4 files changed, 68 insertions(+), 36 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 43e6ad424c7f..129c67ebc81a 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -576,6 +576,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp);
 
+extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+				 unsigned long address, pmd_t *pmdp);
+#define pmdp_collapse_flush pmdp_collapse_flush
+
 #define __HAVE_ARCH_PGTABLE_DEPOSIT
 extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 				       pgtable_t pgtable);
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 59daa5eeec25..9171c1a37290 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -560,41 +560,47 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
 	pmd_t pmd;
 
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-	if (pmd_trans_huge(*pmdp)) {
-		pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
-	} else {
-		/*
-		 * khugepaged calls this for normal pmd
-		 */
-		pmd = *pmdp;
-		pmd_clear(pmdp);
-		/*
-		 * Wait for all pending hash_page to finish. This is needed
-		 * in case of subpage collapse. When we collapse normal pages
-		 * to hugepage, we first clear the pmd, then invalidate all
-		 * the PTE entries. The assumption here is that any low level
-		 * page fault will see a none pmd and take the slow path that
-		 * will wait on mmap_sem. But we could very well be in a
-		 * hash_page with local ptep pointer value. Such a hash page
-		 * can result in adding new HPTE entries for normal subpages.
-		 * That means we could be modifying the page content as we
-		 * copy them to a huge page. So wait for parallel hash_page
-		 * to finish before invalidating HPTE entries. We can do this
-		 * by sending an IPI to all the cpus and executing a dummy
-		 * function there.
-		 */
-		kick_all_cpus_sync();
-		/*
-		 * Now invalidate the hpte entries in the range
-		 * covered by pmd. This make sure we take a
-		 * fault and will find the pmd as none, which will
-		 * result in a major fault which takes mmap_sem and
-		 * hence wait for collapse to complete. Without this
-		 * the __collapse_huge_page_copy can result in copying
-		 * the old content.
-		 */
-		flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
-	}
+	VM_BUG_ON(!pmd_trans_huge(*pmdp));
+	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	return pmd;
+}
+
+pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
+			  pmd_t *pmdp)
+{
+	pmd_t pmd;
+
+	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(pmd_trans_huge(*pmdp));
+
+	pmd = *pmdp;
+	pmd_clear(pmdp);
+	/*
+	 * Wait for all pending hash_page to finish. This is needed
+	 * in case of subpage collapse. When we collapse normal pages
+	 * to hugepage, we first clear the pmd, then invalidate all
+	 * the PTE entries. The assumption here is that any low level
+	 * page fault will see a none pmd and take the slow path that
+	 * will wait on mmap_sem. But we could very well be in a
+	 * hash_page with local ptep pointer value. Such a hash page
+	 * can result in adding new HPTE entries for normal subpages.
+	 * That means we could be modifying the page content as we
+	 * copy them to a huge page. So wait for parallel hash_page
+	 * to finish before invalidating HPTE entries. We can do this
+	 * by sending an IPI to all the cpus and executing a dummy
+	 * function there.
+	 */
+	kick_all_cpus_sync();
+	/*
+	 * Now invalidate the hpte entries in the range
+	 * covered by pmd. This make sure we take a
+	 * fault and will find the pmd as none, which will
+	 * result in a major fault which takes mmap_sem and
+	 * hence wait for collapse to complete. Without this
+	 * the __collapse_huge_page_copy can result in copying
+	 * the old content.
+	 */
+	flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
 	return pmd;
 }
 
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 39f1d6a2b04d..acdcaac77d93 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -189,6 +189,28 @@ extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp);
 #endif
 
+#ifndef pmdp_collapse_flush
+#define pmdp_collapse_flush pmdp_collapse_flush
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+					unsigned long address,
+					pmd_t *pmdp)
+{
+	return pmdp_clear_flush(vma, address, pmdp);
+}
+#define pmdp_collapse_flush pmdp_collapse_flush
+#else
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+					unsigned long address,
+					pmd_t *pmdp)
+{
+	BUILD_BUG();
+	return *pmdp;
+}
+#define pmdp_collapse_flush pmdp_collapse_flush
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif
+
 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
 extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 				       pgtable_t pgtable);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 078832cf3636..88f695a4e38b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2499,7 +2499,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	 * huge and small TLB entries for the same virtual address
 	 * to avoid the risk of CPU bugs in that area.
 	 */
-	_pmd = pmdp_clear_flush(vma, address, pmd);
+	_pmd = pmdp_collapse_flush(vma, address, pmd);
 	spin_unlock(pmd_ptl);
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 
-- 
2.1.4

Re: [PATCH V5 1/3] mm/thp: Split out pmd collpase flush into a separate functions

[Aneesh Kumar K.V]

 diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 39f1d6a2b04d..acdcaac77d93 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -189,6 +189,28 @@ extern void pmdp_splitting_flush(struct vm_area_struct *vma,
>  				 unsigned long address, pmd_t *pmdp);
>  #endif
>
> +#ifndef pmdp_collapse_flush
> +#define pmdp_collapse_flush pmdp_collapse_flush
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
> +					unsigned long address,
> +					pmd_t *pmdp)


extra pmdp_collapse_flush #define here

> +{
> +	return pmdp_clear_flush(vma, address, pmdp);
> +}
> +#define pmdp_collapse_flush pmdp_collapse_flush
> +#else
> +static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
> +					unsigned long address,
> +					pmd_t *pmdp)
> +{
> +	BUILD_BUG();
> +	return *pmdp;
> +}
> +#define pmdp_collapse_flush pmdp_collapse_flush
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> +#endif
> +
>  #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
>  extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
>  				       pgtable_t pgtable);

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index acdcaac77d93..2c3ca89e9aee 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -190,7 +190,6 @@ extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 #endif
 
 #ifndef pmdp_collapse_flush
-#define pmdp_collapse_flush pmdp_collapse_flush
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,

[PATCH V5 2/3] powerpc/mm: Use generic version of pmdp_clear_flush

[Aneesh Kumar K.V]

Also move the pmd_trans_huge check to generic code.

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pgtable-ppc64.h |  4 ----
 arch/powerpc/mm/pgtable_64.c             | 11 -----------
 arch/s390/include/asm/pgtable.h          |  8 ++++++++
 include/asm-generic/pgtable.h            |  7 ++++++-
 mm/pgtable-generic.c                     |  1 +
 5 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 129c67ebc81a..55f06a381dd7 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -557,10 +557,6 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 extern pmd_t pmdp_get_and_clear(struct mm_struct *mm,
 				unsigned long addr, pmd_t *pmdp);
 
-#define __HAVE_ARCH_PMDP_CLEAR_FLUSH
-extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
-			      pmd_t *pmdp);
-
 #define __HAVE_ARCH_PMDP_SET_WRPROTECT
 static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pmd_t *pmdp)
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 9171c1a37290..d37b9d1a1813 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -554,17 +554,6 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	return old;
 }
 
-pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
-		       pmd_t *pmdp)
-{
-	pmd_t pmd;
-
-	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-	VM_BUG_ON(!pmd_trans_huge(*pmdp));
-	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
-	return pmd;
-}
-
 pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 			  pmd_t *pmdp)
 {
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index fc642399b489..17627f73a032 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1548,6 +1548,14 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 	}
 }
 
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+					unsigned long address,
+					pmd_t *pmdp)
+{
+	return pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+}
+#define pmdp_collapse_flush pmdp_collapse_flush
+
 #define pfn_pmd(pfn, pgprot)	mk_pmd_phys(__pa((pfn) << PAGE_SHIFT), (pgprot))
 #define mk_pmd(page, pgprot)	pfn_pmd(page_to_pfn(page), (pgprot))
 
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index acdcaac77d93..3d0273d4dad6 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -196,7 +196,12 @@ static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,
 					pmd_t *pmdp)
 {
-	return pmdp_clear_flush(vma, address, pmdp);
+	pmd_t pmd;
+	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(pmd_trans_huge(*pmdp));
+	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+	return pmd;
 }
 #define pmdp_collapse_flush pmdp_collapse_flush
 #else
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index c25f94b33811..dd9d04f17749 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -126,6 +126,7 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
 {
 	pmd_t pmd;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(!pmd_trans_huge(*pmdp));
 	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
 	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
 	return pmd;
-- 
2.1.4

Re: [PATCH V5 2/3] powerpc/mm: Use generic version of pmdp_clear_flush

[Andrew Morton]

On Fri, 15 May 2015 21:12:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

> Also move the pmd_trans_huge check to generic code.
> 
> ...
>
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -196,7 +196,12 @@ static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
>  					unsigned long address,
>  					pmd_t *pmdp)
>  {
> -	return pmdp_clear_flush(vma, address, pmdp);
> +	pmd_t pmd;
> +	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> +	VM_BUG_ON(pmd_trans_huge(*pmdp));
> +	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
> +	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
> +	return pmd;
>  }

x86_64 allmodconfig:

In file included from ./arch/x86/include/asm/pgtable.h:878,
                 from include/linux/mm.h:53,
                 from include/linux/suspend.h:8,
                 from arch/x86/kernel/asm-offsets.c:12:
include/asm-generic/pgtable.h: In function 'pmdp_collapse_flush':
include/asm-generic/pgtable.h:199: error: 'HPAGE_PMD_MASK' undeclared (first use in this function)
include/asm-generic/pgtable.h:199: error: (Each undeclared identifier is reported only once
include/asm-generic/pgtable.h:199: error: for each function it appears in.)
include/asm-generic/pgtable.h:202: error: implicit declaration of function 'flush_tlb_range'
include/asm-generic/pgtable.h:202: error: 'HPAGE_PMD_SIZE' undeclared (first use in this function)


Including linux/huge_mm.h doesn't work.  A suitable fix would be to
move this into a .c file.

Re: [PATCH V5 2/3] powerpc/mm: Use generic version of pmdp_clear_flush

[Aneesh Kumar K.V]

Andrew Morton <akpm@linux-foundation.org> writes:

> On Fri, 15 May 2015 21:12:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
>
>> Also move the pmd_trans_huge check to generic code.
>> 
>> ...
>>
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -196,7 +196,12 @@ static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
>>  					unsigned long address,
>>  					pmd_t *pmdp)
>>  {
>> -	return pmdp_clear_flush(vma, address, pmdp);
>> +	pmd_t pmd;
>> +	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
>> +	VM_BUG_ON(pmd_trans_huge(*pmdp));
>> +	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
>> +	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
>> +	return pmd;
>>  }
>
> x86_64 allmodconfig:
>
> In file included from ./arch/x86/include/asm/pgtable.h:878,
>                  from include/linux/mm.h:53,
>                  from include/linux/suspend.h:8,
>                  from arch/x86/kernel/asm-offsets.c:12:
> include/asm-generic/pgtable.h: In function 'pmdp_collapse_flush':
> include/asm-generic/pgtable.h:199: error: 'HPAGE_PMD_MASK' undeclared (first use in this function)
> include/asm-generic/pgtable.h:199: error: (Each undeclared identifier is reported only once
> include/asm-generic/pgtable.h:199: error: for each function it appears in.)
> include/asm-generic/pgtable.h:202: error: implicit declaration of function 'flush_tlb_range'
> include/asm-generic/pgtable.h:202: error: 'HPAGE_PMD_SIZE' undeclared (first use in this function)
>

Sorry for the build break. I was mostly focusing on the ppc64 build with
different platforms and was hoping that will include all thp/enable
disable configs. Unfortunately, we needed a config that is thp enabled and
use generic pgtable.h. Will make sure that I test build and boot test on
x86 before sending patch next time.


>
> Including linux/huge_mm.h doesn't work.  A suitable fix would be to
> move this into a .c file.


that helped.

commit 3ef98ff8092789f7b58f3662297a80eff8d757ea
Author: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Date:   Mon May 11 15:53:21 2015 +0530

    powerpc/mm: Use generic version of pmdp_clear_flush
    
    Also move the pmd_trans_huge check to generic code.
    
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 129c67ebc81a..55f06a381dd7 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -557,10 +557,6 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 extern pmd_t pmdp_get_and_clear(struct mm_struct *mm,
 				unsigned long addr, pmd_t *pmdp);
 
-#define __HAVE_ARCH_PMDP_CLEAR_FLUSH
-extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
-			      pmd_t *pmdp);
-
 #define __HAVE_ARCH_PMDP_SET_WRPROTECT
 static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pmd_t *pmdp)
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index 9171c1a37290..d37b9d1a1813 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -554,17 +554,6 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	return old;
 }
 
-pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
-		       pmd_t *pmdp)
-{
-	pmd_t pmd;
-
-	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-	VM_BUG_ON(!pmd_trans_huge(*pmdp));
-	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
-	return pmd;
-}
-
 pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 			  pmd_t *pmdp)
 {
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index fc642399b489..17627f73a032 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1548,6 +1548,14 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 	}
 }
 
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+					unsigned long address,
+					pmd_t *pmdp)
+{
+	return pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+}
+#define pmdp_collapse_flush pmdp_collapse_flush
+
 #define pfn_pmd(pfn, pgprot)	mk_pmd_phys(__pa((pfn) << PAGE_SHIFT), (pgprot))
 #define mk_pmd(page, pgprot)	pfn_pmd(page_to_pfn(page), (pgprot))
 
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 2c3ca89e9aee..3b5a89ab4103 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -191,13 +191,8 @@ extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 
 #ifndef pmdp_collapse_flush
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
-					unsigned long address,
-					pmd_t *pmdp)
-{
-	return pmdp_clear_flush(vma, address, pmdp);
-}
-#define pmdp_collapse_flush pmdp_collapse_flush
+extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+				 unsigned long address, pmd_t *pmdp);
 #else
 static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index c25f94b33811..7f2314f9e16f 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -126,6 +126,7 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
 {
 	pmd_t pmd;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(!pmd_trans_huge(*pmdp));
 	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
 	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
 	return pmd;
@@ -198,3 +199,18 @@ void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
+
+#ifndef pmdp_collapse_flush
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
+			  pmd_t *pmdp)
+{
+	pmd_t pmd;
+	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(pmd_trans_huge(*pmdp));
+	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
+	return pmd;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif

[PATCH V5 3/3] mm: Clarify that the function operates on hugepage pte

[Aneesh Kumar K.V]

We have confusing functions to clear pmd, pmd_clear_* and pmd_clear.
Add _huge_ to pmdp_clear functions so that we are clear that they
operate on hugepage pte.

We don't bother about other functions like pmdp_set_wrprotect,
pmdp_clear_flush_young, because they operate on PTE bits and hence
indicate they are operating on hugepage ptes

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/mips/include/asm/pgtable.h          |  8 ++++----
 arch/powerpc/include/asm/pgtable-ppc64.h |  6 +++---
 arch/powerpc/mm/pgtable_64.c             |  4 ++--
 arch/s390/include/asm/pgtable.h          | 24 ++++++++++++------------
 arch/sparc/include/asm/pgtable_64.h      |  8 ++++----
 arch/tile/include/asm/pgtable.h          |  8 ++++----
 arch/x86/include/asm/pgtable.h           |  4 ++--
 include/asm-generic/pgtable.h            | 24 ++++++++++++++----------
 include/linux/mmu_notifier.h             | 12 ++++++------
 mm/huge_memory.c                         | 16 ++++++++--------
 mm/migrate.c                             |  2 +-
 mm/pgtable-generic.c                     |  8 ++++----
 mm/rmap.c                                |  2 +-
 13 files changed, 65 insertions(+), 61 deletions(-)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 819af9d057a8..9d8106758142 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -568,12 +568,12 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
 }
 
 /*
- * The generic version pmdp_get_and_clear uses a version of pmd_clear() with a
+ * The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
  * different prototype.
  */
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				       unsigned long address, pmd_t *pmdp)
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long address, pmd_t *pmdp)
 {
 	pmd_t old = *pmdp;
 
diff --git a/arch/powerpc/include/asm/pgtable-ppc64.h b/arch/powerpc/include/asm/pgtable-ppc64.h
index 55f06a381dd7..c378988dc6cf 100644
--- a/arch/powerpc/include/asm/pgtable-ppc64.h
+++ b/arch/powerpc/include/asm/pgtable-ppc64.h
@@ -553,9 +553,9 @@ extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 				  unsigned long address, pmd_t *pmdp);
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-extern pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				unsigned long addr, pmd_t *pmdp);
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+extern pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+				     unsigned long addr, pmd_t *pmdp);
 
 #define __HAVE_ARCH_PMDP_SET_WRPROTECT
 static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index d37b9d1a1813..ad0f63628678 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -812,8 +812,8 @@ void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
 	return;
 }
 
-pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-			 unsigned long addr, pmd_t *pmdp)
+pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+			      unsigned long addr, pmd_t *pmdp)
 {
 	pmd_t old_pmd;
 	pgtable_t pgtable;
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 17627f73a032..414e7f6fd256 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1498,9 +1498,9 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 	return pmd_young(pmd);
 }
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				       unsigned long address, pmd_t *pmdp)
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long address, pmd_t *pmdp)
 {
 	pmd_t pmd = *pmdp;
 
@@ -1509,10 +1509,10 @@ static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
 	return pmd;
 }
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR_FULL
-static inline pmd_t pmdp_get_and_clear_full(struct mm_struct *mm,
-					    unsigned long address,
-					    pmd_t *pmdp, int full)
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL
+static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
+						 unsigned long address,
+						 pmd_t *pmdp, int full)
 {
 	pmd_t pmd = *pmdp;
 
@@ -1522,11 +1522,11 @@ static inline pmd_t pmdp_get_and_clear_full(struct mm_struct *mm,
 	return pmd;
 }
 
-#define __HAVE_ARCH_PMDP_CLEAR_FLUSH
-static inline pmd_t pmdp_clear_flush(struct vm_area_struct *vma,
-				     unsigned long address, pmd_t *pmdp)
+#define __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
+static inline pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
+					  unsigned long address, pmd_t *pmdp)
 {
-	return pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	return pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
 }
 
 #define __HAVE_ARCH_PMDP_INVALIDATE
@@ -1552,7 +1552,7 @@ static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,
 					pmd_t *pmdp)
 {
-	return pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	return pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
 }
 #define pmdp_collapse_flush pmdp_collapse_flush
 
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index dc165ebdf05a..2b72f651f393 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -845,10 +845,10 @@ static inline unsigned long pud_pfn(pud_t pud)
 void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
 		   pte_t *ptep, pte_t orig, int fullmm);
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				       unsigned long addr,
-				       pmd_t *pmdp)
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long addr,
+					    pmd_t *pmdp)
 {
 	pmd_t pmd = *pmdp;
 	set_pmd_at(mm, addr, pmdp, __pmd(0UL));
diff --git a/arch/tile/include/asm/pgtable.h b/arch/tile/include/asm/pgtable.h
index 95a4f19d16c5..2b05ccbebed9 100644
--- a/arch/tile/include/asm/pgtable.h
+++ b/arch/tile/include/asm/pgtable.h
@@ -414,10 +414,10 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 }
 
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				       unsigned long address,
-				       pmd_t *pmdp)
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long address,
+					    pmd_t *pmdp)
 {
 	return pte_pmd(ptep_get_and_clear(mm, address, pmdp_ptep(pmdp)));
 }
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index fe57e7a98839..25add5e44f0a 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -799,8 +799,8 @@ static inline int pmd_write(pmd_t pmd)
 	return pmd_flags(pmd) & _PAGE_RW;
 }
 
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm, unsigned long addr,
+#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, unsigned long addr,
 				       pmd_t *pmdp)
 {
 	pmd_t pmd = native_pmdp_get_and_clear(pmdp);
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 3d0273d4dad6..1ee1260d5386 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -96,11 +96,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 }
 #endif
 
-#ifndef __HAVE_ARCH_PMDP_GET_AND_CLEAR
+#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
-				       unsigned long address,
-				       pmd_t *pmdp)
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long address,
+					    pmd_t *pmdp)
 {
 	pmd_t pmd = *pmdp;
 	pmd_clear(pmdp);
@@ -109,13 +109,13 @@ static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm,
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
 
-#ifndef __HAVE_ARCH_PMDP_GET_AND_CLEAR_FULL
+#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline pmd_t pmdp_get_and_clear_full(struct mm_struct *mm,
+static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
 					    unsigned long address, pmd_t *pmdp,
 					    int full)
 {
-	return pmdp_get_and_clear(mm, address, pmdp);
+	return pmdp_huge_get_and_clear(mm, address, pmdp);
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif
@@ -152,8 +152,8 @@ extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
 			      pte_t *ptep);
 #endif
 
-#ifndef __HAVE_ARCH_PMDP_CLEAR_FLUSH
-extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma,
+#ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
+extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
 			      unsigned long address,
 			      pmd_t *pmdp);
 #endif
@@ -196,10 +196,14 @@ static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,
 					pmd_t *pmdp)
 {
+	/*
+	 * pmd and hugepage pte format are same. So we could
+	 * use the same function.
+	 */
 	pmd_t pmd;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 	VM_BUG_ON(pmd_trans_huge(*pmdp));
-	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
 	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
 	return pmd;
 }
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 95243d28a0ee..61cd67f4d788 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -324,25 +324,25 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 	___pte;								\
 })
 
-#define pmdp_clear_flush_notify(__vma, __haddr, __pmd)			\
+#define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd)		\
 ({									\
 	unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;		\
 	struct mm_struct *___mm = (__vma)->vm_mm;			\
 	pmd_t ___pmd;							\
 									\
-	___pmd = pmdp_clear_flush(__vma, __haddr, __pmd);		\
+	___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd);		\
 	mmu_notifier_invalidate_range(___mm, ___haddr,			\
 				      ___haddr + HPAGE_PMD_SIZE);	\
 									\
 	___pmd;								\
 })
 
-#define pmdp_get_and_clear_notify(__mm, __haddr, __pmd)			\
+#define pmdp_huge_get_and_clear_notify(__mm, __haddr, __pmd)		\
 ({									\
 	unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;		\
 	pmd_t ___pmd;							\
 									\
-	___pmd = pmdp_get_and_clear(__mm, __haddr, __pmd);		\
+	___pmd = pmdp_huge_get_and_clear(__mm, __haddr, __pmd);		\
 	mmu_notifier_invalidate_range(__mm, ___haddr,			\
 				      ___haddr + HPAGE_PMD_SIZE);	\
 									\
@@ -428,8 +428,8 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
 #define	ptep_clear_flush_notify ptep_clear_flush
-#define pmdp_clear_flush_notify pmdp_clear_flush
-#define pmdp_get_and_clear_notify pmdp_get_and_clear
+#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
+#define pmdp_huge_get_and_clear_notify pmdp_huge_get_and_clear
 #define set_pte_at_notify set_pte_at
 
 #endif /* CONFIG_MMU_NOTIFIER */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 88f695a4e38b..c19adcb2c324 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1031,7 +1031,7 @@ static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
 		goto out_free_pages;
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 
-	pmdp_clear_flush_notify(vma, haddr, pmd);
+	pmdp_huge_clear_flush_notify(vma, haddr, pmd);
 	/* leave pmd empty until pte is filled */
 
 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
@@ -1174,7 +1174,7 @@ alloc:
 		pmd_t entry;
 		entry = mk_huge_pmd(new_page, vma->vm_page_prot);
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
-		pmdp_clear_flush_notify(vma, haddr, pmd);
+		pmdp_huge_clear_flush_notify(vma, haddr, pmd);
 		page_add_new_anon_rmap(new_page, vma, haddr);
 		mem_cgroup_commit_charge(new_page, memcg, false);
 		lru_cache_add_active_or_unevictable(new_page, vma);
@@ -1396,12 +1396,12 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		pmd_t orig_pmd;
 		/*
 		 * For architectures like ppc64 we look at deposited pgtable
-		 * when calling pmdp_get_and_clear. So do the
+		 * when calling pmdp_huge_get_and_clear. So do the
 		 * pgtable_trans_huge_withdraw after finishing pmdp related
 		 * operations.
 		 */
-		orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd,
-						   tlb->fullmm);
+		orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
+							tlb->fullmm);
 		tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
 		pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
 		if (is_huge_zero_pmd(orig_pmd)) {
@@ -1459,7 +1459,7 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
 		new_ptl = pmd_lockptr(mm, new_pmd);
 		if (new_ptl != old_ptl)
 			spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
-		pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
+		pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
 		VM_BUG_ON(!pmd_none(*new_pmd));
 
 		if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
@@ -1505,7 +1505,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		}
 
 		if (!prot_numa || !pmd_protnone(*pmd)) {
-			entry = pmdp_get_and_clear_notify(mm, addr, pmd);
+			entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
 			entry = pmd_modify(entry, newprot);
 			if (preserve_write)
 				entry = pmd_mkwrite(entry);
@@ -2865,7 +2865,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
 	pmd_t _pmd;
 	int i;
 
-	pmdp_clear_flush_notify(vma, haddr, pmd);
+	pmdp_huge_clear_flush_notify(vma, haddr, pmd);
 	/* leave pmd empty until pte is filled */
 
 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
diff --git a/mm/migrate.c b/mm/migrate.c
index f53838fe3dfe..c37d5772767b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1796,7 +1796,7 @@ fail_putback:
 	 */
 	flush_cache_range(vma, mmun_start, mmun_end);
 	page_add_anon_rmap(new_page, vma, mmun_start);
-	pmdp_clear_flush_notify(vma, mmun_start, pmd);
+	pmdp_huge_clear_flush_notify(vma, mmun_start, pmd);
 	set_pmd_at(mm, mmun_start, pmd, entry);
 	flush_tlb_range(vma, mmun_start, mmun_end);
 	update_mmu_cache_pmd(vma, address, &entry);
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index dd9d04f17749..af063ad47d55 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -119,15 +119,15 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
 }
 #endif
 
-#ifndef __HAVE_ARCH_PMDP_CLEAR_FLUSH
+#ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
-		       pmd_t *pmdp)
+pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,
+			    pmd_t *pmdp)
 {
 	pmd_t pmd;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 	VM_BUG_ON(!pmd_trans_huge(*pmdp));
-	pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
+	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
 	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
 	return pmd;
 }
diff --git a/mm/rmap.c b/mm/rmap.c
index 24dd3f9fee27..6f94e4502c49 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -625,7 +625,7 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
 
 	pmd = pmd_offset(pud, address);
 	/*
-	 * Some THP functions use the sequence pmdp_clear_flush(), set_pmd_at()
+	 * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
 	 * without holding anon_vma lock for write.  So when looking for a
 	 * genuine pmde (in which to find pte), test present and !THP together.
 	 */
-- 
2.1.4

Re: [PATCH V5 0/3] THP related cleanups

[Andrew Morton]

On Fri, 15 May 2015 21:12:27 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

> Changes from V4:
> * Folded patches in -mm
>   mm-thp-split-out-pmd-collpase-flush-into-a-separate-functions-fix.patch
>   mm-thp-split-out-pmd-collpase-flush-into-a-separate-functions-fix-2.patch
>   mm-clarify-that-the-function-operateds-on-hugepage-pte-fix.patch
> * Fix VM_BUG_ON on x86.
>  the default implementation of pmdp_collapse_flush used the hugepage variant
>  and hence can be called on pmd_t pointing to pgtable. This resulting in us
>  hitting VM_BUG_ON in pmdp_clear_flush. Update powerpc/mm: Use generic version of pmdp_clear_flush
>  to handle this.
> 
> 
> NOTE: Can we get this tested on s390 ?

fwiw, I build tested s390 allmodconfig in mm/ and arch/s390, no issues.