From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
The current get_user_pages() code is a wee bit more complicated
than it needs to be for pte bit checking. Currently, it establishes
a mask of required pte _PAGE_* bits and ensures that the pte it
goes after has all those bits.
This consolidates the three identical copies of this code.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
b/arch/x86/mm/gup.c | 39 ++++++++++++++++++++++-----------------
1 file changed, 22 insertions(+), 17 deletions(-)
diff -puN arch/x86/mm/gup.c~pkeys-12-gup-swizzle arch/x86/mm/gup.c
--- a/arch/x86/mm/gup.c~pkeys-12-gup-swizzle 2016-01-06 15:50:09.552333717 -0800
+++ b/arch/x86/mm/gup.c 2016-01-06 15:50:09.555333852 -0800
@@ -64,6 +64,24 @@ retry:
}
/*
+ * 'pteval' can come from a pte, pmd or pud. We only check
+ * _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
+ * same value on all 3 types.
+ */
+static inline int pte_allows_gup(unsigned long pteval, int write)
+{
+ unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
+
+ if (write)
+ need_pte_bits |= _PAGE_RW;
+
+ if ((pteval & need_pte_bits) != need_pte_bits)
+ return 0;
+
+ return 1;
+}
+
+/*
* The performance critical leaf functions are made noinline otherwise gcc
* inlines everything into a single function which results in too much
* register pressure.
@@ -71,13 +89,8 @@ retry:
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
- unsigned long mask;
pte_t *ptep;
- mask = _PAGE_PRESENT|_PAGE_USER;
- if (write)
- mask |= _PAGE_RW;
-
ptep = pte_offset_map(&pmd, addr);
do {
pte_t pte = gup_get_pte(ptep);
@@ -88,8 +101,8 @@ static noinline int gup_pte_range(pmd_t
pte_unmap(ptep);
return 0;
}
-
- if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
+ if (!pte_allows_gup(pte_val(pte), write) ||
+ pte_special(pte)) {
pte_unmap(ptep);
return 0;
}
@@ -117,14 +130,10 @@ static inline void get_head_page_multipl
static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
- unsigned long mask;
struct page *head, *page;
int refs;
- mask = _PAGE_PRESENT|_PAGE_USER;
- if (write)
- mask |= _PAGE_RW;
- if ((pmd_flags(pmd) & mask) != mask)
+ if (!pte_allows_gup(pmd_val(pmd), write))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
@@ -193,14 +202,10 @@ static int gup_pmd_range(pud_t pud, unsi
static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
- unsigned long mask;
struct page *head, *page;
int refs;
- mask = _PAGE_PRESENT|_PAGE_USER;
- if (write)
- mask |= _PAGE_RW;
- if ((pud_flags(pud) & mask) != mask)
+ if (!pte_allows_gup(pud_val(pud), write))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
_
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