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Message-Id: <20151204011446.DDC6435F@viggo.jf.intel.com>
Date: Thu, 03 Dec 2015 17:14:46 -0800
From: Dave Hansen <dave@...1.net>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, x86@...nel.org, Dave Hansen <dave@...1.net>,
dave.hansen@...ux.intel.com
Subject: [PATCH 16/34] x86, mm: simplify get_user_pages() PTE bit handling
From: Dave Hansen <dave.hansen@...ux.intel.com>
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@...ux.intel.com>
---
b/arch/x86/mm/gup.c | 45 ++++++++++++++++++++++++++++-----------------
1 file changed, 28 insertions(+), 17 deletions(-)
diff -puN arch/x86/mm/gup.c~pkeys-16-gup-swizzle arch/x86/mm/gup.c
--- a/arch/x86/mm/gup.c~pkeys-16-gup-swizzle 2015-12-03 16:21:25.148649631 -0800
+++ b/arch/x86/mm/gup.c 2015-12-03 16:21:25.151649767 -0800
@@ -63,6 +63,30 @@ retry:
#endif
}
+static inline int pte_allows_gup(pte_t pte, int write)
+{
+ /*
+ * 'pte' can reall be 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.
+ */
+ if (!(pte_flags(pte) & (_PAGE_PRESENT|_PAGE_USER)))
+ return 0;
+ if (write && !(pte_write(pte)))
+ return 0;
+ return 1;
+}
+
+static inline int pmd_allows_gup(pmd_t pmd, int write)
+{
+ return pte_allows_gup(*(pte_t *)&pmd, write);
+}
+
+static inline int pud_allows_gup(pud_t pud, int write)
+{
+ return pte_allows_gup(*(pte_t *)&pud, write);
+}
+
/*
* The performance critical leaf functions are made noinline otherwise gcc
* inlines everything into a single function which results in too much
@@ -71,13 +95,8 @@ 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 +107,8 @@ 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, write) ||
+ pte_special(pte)) {
pte_unmap(ptep);
return 0;
}
@@ -117,14 +136,10 @@ 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 (!pmd_allows_gup(pmd, write))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
@@ -193,14 +208,10 @@ 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 (!pud_allows_gup(pud, write))
return 0;
/* hugepages are never "special" */
VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
_
--
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