[PATCH v3 1/6] mm/hugetlb: reduce arch dependent code around follow_huge_*

From: Naoya Horiguchi
Date: Thu Aug 28 2014 - 21:40:59 EST

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Currently we have many duplicates in definitions around follow_huge_addr(),
follow_huge_pmd(), and follow_huge_pud(), so this patch tries to remove them.
The basic idea is to put the default implementation for these functions in
mm/hugetlb.c as weak symbols (regardless of CONFIG_ARCH_WANT_GENERAL_HUGETLB),
and to implement arch-specific code only when the arch needs it.

For follow_huge_addr(), only powerpc and ia64 have their own implementation,
and in all other architectures this function just returns ERR_PTR(-EINVAL).
So this patch sets returning ERR_PTR(-EINVAL) as default.

As for follow_huge_(pmd|pud)(), if (pmd|pud)_huge() is implemented to always
return 0 in your architecture (like in ia64 or sparc,) it's never called
(the callsite is optimized away) no matter how implemented it is.
So in such architectures, we don't need arch-specific implementation.

In some architecture (like mips, s390 and tile,) their current arch-specific
follow_huge_(pmd|pud)() are effectively identical with the common code,
so this patch lets these architecture use the common code.

One exception is metag, where pmd_huge() could return non-zero but it expects
follow_huge_pmd() to always return NULL. This means that we need arch-specific
implementation which returns NULL. This behavior looks strange to me (because
non-zero pmd_huge() implies that the architecture supports PMD-based hugepage,
so follow_huge_pmd() can/should return some relevant value,) but that's beyond
this cleanup patch, so let's keep it.

Justification of non-trivial changes:
- in s390, follow_huge_pmd() checks !MACHINE_HAS_HPAGE at first, and this
patch removes the check. This is OK because we can assume MACHINE_HAS_HPAGE
is true when follow_huge_pmd() can be called (note that pmd_huge() has
the same check and always returns 0 for !MACHINE_HAS_HPAGE.)
- in s390 and mips, we use HPAGE_MASK instead of PMD_MASK as done in common
code. This patch forces these archs use PMD_MASK, but it's OK because
they are identical in both archs.
In s390, both of HPAGE_SHIFT and PMD_SHIFT are 20.
In mips, HPAGE_SHIFT is defined as (PAGE_SHIFT + PAGE_SHIFT - 3) and
PMD_SHIFT is define as (PAGE_SHIFT + PAGE_SHIFT + PTE_ORDER - 3), but
PTE_ORDER is always 0, so these are identical.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
arch/arm/mm/hugetlbpage.c | 6 ------
arch/arm64/mm/hugetlbpage.c | 6 ------
arch/ia64/mm/hugetlbpage.c | 6 ------
arch/metag/mm/hugetlbpage.c | 6 ------
arch/mips/mm/hugetlbpage.c | 18 ------------------
arch/powerpc/mm/hugetlbpage.c | 8 ++++++++
arch/s390/mm/hugetlbpage.c | 20 --------------------
arch/sh/mm/hugetlbpage.c | 12 ------------
arch/sparc/mm/hugetlbpage.c | 12 ------------
arch/tile/mm/hugetlbpage.c | 28 ----------------------------
arch/x86/mm/hugetlbpage.c | 12 ------------
mm/hugetlb.c | 30 +++++++++++++++---------------
12 files changed, 23 insertions(+), 141 deletions(-)

diff --git mmotm-2014-08-25-16-52.orig/arch/arm/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/arm/mm/hugetlbpage.c
index 66781bf34077..c72412415093 100644
--- mmotm-2014-08-25-16-52.orig/arch/arm/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/arm/mm/hugetlbpage.c
@@ -36,12 +36,6 @@
* of type casting from pmd_t * to pte_t *.
*/

-struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
- int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pud_huge(pud_t pud)
{
return 0;
diff --git mmotm-2014-08-25-16-52.orig/arch/arm64/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/arm64/mm/hugetlbpage.c
index 023747bf4dd7..2de9d2e59d96 100644
--- mmotm-2014-08-25-16-52.orig/arch/arm64/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/arm64/mm/hugetlbpage.c
@@ -38,12 +38,6 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
}
#endif

-struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
- int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return !(pmd_val(pmd) & PMD_TABLE_BIT);
diff --git mmotm-2014-08-25-16-52.orig/arch/ia64/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/ia64/mm/hugetlbpage.c
index 76069c18ee42..52b7604b5215 100644
--- mmotm-2014-08-25-16-52.orig/arch/ia64/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/ia64/mm/hugetlbpage.c
@@ -114,12 +114,6 @@ int pud_huge(pud_t pud)
return 0;
}

-struct page *
-follow_huge_pmd(struct mm_struct *mm, unsigned long address, pmd_t *pmd, int write)
-{
- return NULL;
-}
-
void hugetlb_free_pgd_range(struct mmu_gather *tlb,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
diff --git mmotm-2014-08-25-16-52.orig/arch/metag/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/metag/mm/hugetlbpage.c
index 3c52fa6d0f8e..745081427659 100644
--- mmotm-2014-08-25-16-52.orig/arch/metag/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/metag/mm/hugetlbpage.c
@@ -94,12 +94,6 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
return 0;
}

-struct page *follow_huge_addr(struct mm_struct *mm,
- unsigned long address, int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return pmd_page_shift(pmd) > PAGE_SHIFT;
diff --git mmotm-2014-08-25-16-52.orig/arch/mips/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/mips/mm/hugetlbpage.c
index 4ec8ee10d371..06e0f421b41b 100644
--- mmotm-2014-08-25-16-52.orig/arch/mips/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/mips/mm/hugetlbpage.c
@@ -68,12 +68,6 @@ int is_aligned_hugepage_range(unsigned long addr, unsigned long len)
return 0;
}

-struct page *
-follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return (pmd_val(pmd) & _PAGE_HUGE) != 0;
@@ -83,15 +77,3 @@ int pud_huge(pud_t pud)
{
return (pud_val(pud) & _PAGE_HUGE) != 0;
}
-
-struct page *
-follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
-{
- struct page *page;
-
- page = pte_page(*(pte_t *)pmd);
- if (page)
- page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
- return page;
-}
diff --git mmotm-2014-08-25-16-52.orig/arch/powerpc/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/powerpc/mm/hugetlbpage.c
index 7e70ae968e5f..9517a93a315c 100644
--- mmotm-2014-08-25-16-52.orig/arch/powerpc/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/powerpc/mm/hugetlbpage.c
@@ -706,6 +706,14 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
return NULL;
}

+struct page *
+follow_huge_pud(struct mm_struct *mm, unsigned long address,
+ pmd_t *pmd, int write)
+{
+ BUG();
+ return NULL;
+}
+
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
{
diff --git mmotm-2014-08-25-16-52.orig/arch/s390/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/s390/mm/hugetlbpage.c
index 0ff66a7e29bb..811e7f9a2de0 100644
--- mmotm-2014-08-25-16-52.orig/arch/s390/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/s390/mm/hugetlbpage.c
@@ -201,12 +201,6 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
return 0;
}

-struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
- int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
if (!MACHINE_HAS_HPAGE)
@@ -219,17 +213,3 @@ int pud_huge(pud_t pud)
{
return 0;
}
-
-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmdp, int write)
-{
- struct page *page;
-
- if (!MACHINE_HAS_HPAGE)
- return NULL;
-
- page = pmd_page(*pmdp);
- if (page)
- page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
- return page;
-}
diff --git mmotm-2014-08-25-16-52.orig/arch/sh/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/sh/mm/hugetlbpage.c
index d7762349ea48..534bc978af8a 100644
--- mmotm-2014-08-25-16-52.orig/arch/sh/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/sh/mm/hugetlbpage.c
@@ -67,12 +67,6 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
return 0;
}

-struct page *follow_huge_addr(struct mm_struct *mm,
- unsigned long address, int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return 0;
@@ -82,9 +76,3 @@ int pud_huge(pud_t pud)
{
return 0;
}
-
-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
-{
- return NULL;
-}
diff --git mmotm-2014-08-25-16-52.orig/arch/sparc/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/sparc/mm/hugetlbpage.c
index d329537739c6..4242eab12e10 100644
--- mmotm-2014-08-25-16-52.orig/arch/sparc/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/sparc/mm/hugetlbpage.c
@@ -215,12 +215,6 @@ pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
return entry;
}

-struct page *follow_huge_addr(struct mm_struct *mm,
- unsigned long address, int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return 0;
@@ -230,9 +224,3 @@ int pud_huge(pud_t pud)
{
return 0;
}
-
-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
-{
- return NULL;
-}
diff --git mmotm-2014-08-25-16-52.orig/arch/tile/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/tile/mm/hugetlbpage.c
index e514899e1100..8a00c7b7b862 100644
--- mmotm-2014-08-25-16-52.orig/arch/tile/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/tile/mm/hugetlbpage.c
@@ -150,12 +150,6 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
return NULL;
}

-struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
- int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return !!(pmd_val(pmd) & _PAGE_HUGE_PAGE);
@@ -166,28 +160,6 @@ int pud_huge(pud_t pud)
return !!(pud_val(pud) & _PAGE_HUGE_PAGE);
}

-struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
-{
- struct page *page;
-
- page = pte_page(*(pte_t *)pmd);
- if (page)
- page += ((address & ~PMD_MASK) >> PAGE_SHIFT);
- return page;
-}
-
-struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
- pud_t *pud, int write)
-{
- struct page *page;
-
- page = pte_page(*(pte_t *)pud);
- if (page)
- page += ((address & ~PUD_MASK) >> PAGE_SHIFT);
- return page;
-}
-
int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
{
return 0;
diff --git mmotm-2014-08-25-16-52.orig/arch/x86/mm/hugetlbpage.c mmotm-2014-08-25-16-52/arch/x86/mm/hugetlbpage.c
index 8b977ebf9388..03b8a7c11817 100644
--- mmotm-2014-08-25-16-52.orig/arch/x86/mm/hugetlbpage.c
+++ mmotm-2014-08-25-16-52/arch/x86/mm/hugetlbpage.c
@@ -52,20 +52,8 @@ int pud_huge(pud_t pud)
return 0;
}

-struct page *
-follow_huge_pmd(struct mm_struct *mm, unsigned long address,
- pmd_t *pmd, int write)
-{
- return NULL;
-}
#else

-struct page *
-follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
-{
- return ERR_PTR(-EINVAL);
-}
-
int pmd_huge(pmd_t pmd)
{
return !!(pmd_val(pmd) & _PAGE_PSE);
diff --git mmotm-2014-08-25-16-52.orig/mm/hugetlb.c mmotm-2014-08-25-16-52/mm/hugetlb.c
index eeceeeb09019..022767506c7b 100644
--- mmotm-2014-08-25-16-52.orig/mm/hugetlb.c
+++ mmotm-2014-08-25-16-52/mm/hugetlb.c
@@ -3653,7 +3653,20 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
return (pte_t *) pmd;
}

-struct page *
+#endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
+
+/*
+ * These functions are overwritable if your architecture needs its own
+ * behavior.
+ */
+struct page * __weak
+follow_huge_addr(struct mm_struct *mm, unsigned long address,
+ int write)
+{
+ return ERR_PTR(-EINVAL);
+}
+
+struct page * __weak
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int write)
{
@@ -3665,7 +3678,7 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
return page;
}

-struct page *
+struct page * __weak
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int write)
{
@@ -3677,19 +3690,6 @@ follow_huge_pud(struct mm_struct *mm, unsigned long address,
return page;
}

-#else /* !CONFIG_ARCH_WANT_GENERAL_HUGETLB */
-
-/* Can be overriden by architectures */
-struct page * __weak
-follow_huge_pud(struct mm_struct *mm, unsigned long address,
- pud_t *pud, int write)
-{
- BUG();
- return NULL;
-}
-
-#endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
-
#ifdef CONFIG_MEMORY_FAILURE

/* Should be called in hugetlb_lock */
--
1.9.3

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Next message: Alexander Holler: "Re: [RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT)"
Previous message: Naoya Horiguchi: "[PATCH v3 4/6] mm/hugetlb: add migration entry check in hugetlb_change_protection"
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