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x86/mm/gup: Simplify get_user_pages() PTE bit handling

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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@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210218.3A2D4045@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dave Hansen 2016-02-12 13:02:18 -08:00 committed by Ingo Molnar
parent d4925e00d5
commit 1874f6895c
1 changed files with 22 additions and 16 deletions
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38
arch/x86/mm/gup.c
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@ -74,6 +74,24 @@ static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
}
}
/*
* '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
@ -83,14 +101,9 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
struct dev_pagemap *pgmap = NULL;
unsigned long mask;
int nr_start = *nr;
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);
@ -110,7 +123,8 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
pte_unmap(ptep);
return 0;
}
} else if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
} else if (!pte_allows_gup(pte_val(pte), write) ||
pte_special(pte)) {
pte_unmap(ptep);
return 0;
}
@ -164,14 +178,10 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
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;
VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
@ -231,14 +241,10 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
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);