[PATCH 3.19 24/27] mm/hugetlb: reduce arch dependent code around follow_huge_*

From: Greg Kroah-Hartman
Date: Sun Apr 26 2015 - 10:18:18 EST

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3.19-stable review patch. If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

commit 61f77eda9bbf0d2e922197ed2dcf88638a639ce5 upstream.

Currently we have many duplicates in definitions around
follow_huge_addr(), follow_huge_pmd(), and follow_huge_pud(), so this
patch tries to remove the m. 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_HUGETL B), 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.

[n-horiguchi@xxxxxxxxxxxxx: resolve conflict to apply to v3.19.1]
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: James Hogan <james.hogan@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
Cc: Lee Schermerhorn <lee.schermerhorn@xxxxxx>
Cc: Steve Capper <steve.capper@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)

--- a/arch/arm/mm/hugetlbpage.c
+++ b/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;
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -38,12 +38,6 @@ int huge_pmd_unshare(struct mm_struct *m
}
#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);
--- a/arch/ia64/mm/hugetlbpage.c
+++ b/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)
--- a/arch/metag/mm/hugetlbpage.c
+++ b/arch/metag/mm/hugetlbpage.c
@@ -94,12 +94,6 @@ int huge_pmd_unshare(struct mm_struct *m
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;
--- a/arch/mips/mm/hugetlbpage.c
+++ b/arch/mips/mm/hugetlbpage.c
@@ -68,12 +68,6 @@ int is_aligned_hugepage_range(unsigned l
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;
-}
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -714,6 +714,14 @@ follow_huge_pmd(struct mm_struct *mm, un
return NULL;
}

+struct page *
+follow_huge_pud(struct mm_struct *mm, unsigned long address,
+ pud_t *pud, int write)
+{
+ BUG();
+ return NULL;
+}
+
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
{
--- a/arch/s390/mm/hugetlbpage.c
+++ b/arch/s390/mm/hugetlbpage.c
@@ -192,12 +192,6 @@ int huge_pmd_unshare(struct mm_struct *m
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)
@@ -210,17 +204,3 @@ 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;
-}
--- a/arch/sh/mm/hugetlbpage.c
+++ b/arch/sh/mm/hugetlbpage.c
@@ -67,12 +67,6 @@ int huge_pmd_unshare(struct mm_struct *m
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;
-}
--- a/arch/sparc/mm/hugetlbpage.c
+++ b/arch/sparc/mm/hugetlbpage.c
@@ -215,12 +215,6 @@ pte_t huge_ptep_get_and_clear(struct mm_
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;
-}
--- a/arch/tile/mm/hugetlbpage.c
+++ b/arch/tile/mm/hugetlbpage.c
@@ -150,12 +150,6 @@ pte_t *huge_pte_offset(struct mm_struct
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;
--- a/arch/x86/mm/hugetlbpage.c
+++ b/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);
-}
-
/*
* pmd_huge() returns 1 if @pmd is hugetlb related entry, that is normal
* hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry.
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3700,7 +3700,20 @@ pte_t *huge_pte_offset(struct mm_struct
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)
{
@@ -3714,7 +3727,7 @@ follow_huge_pmd(struct mm_struct *mm, un
return page;
}

-struct page *
+struct page * __weak
follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int write)
{
@@ -3726,19 +3739,6 @@ follow_huge_pud(struct mm_struct *mm, un
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 */

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