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rmap: extend try_to_unmap() to be usable by split_huge_page()

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Add support for two ttu_flags:

  - TTU_SPLIT_HUGE_PMD would split PMD if it's there, before trying to
    unmap page;

  - TTU_RMAP_LOCKED indicates that caller holds relevant rmap lock;

Also, change rwc->done to !page_mapcount() instead of !page_mapped().
try_to_unmap() works on pte level, so we are really interested in the
mappedness of this small page rather than of the compound page it's a
part of.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-03-17 14:20:04 -07:00 committed by Linus Torvalds
parent b97731992d
commit 2a52bcbcc6
4 changed files with 27 additions and 12 deletions
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7
include/linux/huge_mm.h
View File

@ -106,6 +106,9 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
__split_huge_pmd(__vma, __pmd, __address); \
} while (0)
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address);
#if HPAGE_PMD_ORDER >= MAX_ORDER
#error "hugepages can't be allocated by the buddy allocator"
#endif
@ -173,6 +176,10 @@ static inline int split_huge_page(struct page *page)
static inline void deferred_split_huge_page(struct page *page) {}
#define split_huge_pmd(__vma, __pmd, __address) \
do { } while (0)
static inline void split_huge_pmd_address(struct vm_area_struct *vma,
unsigned long address) {}
static inline int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{

3
include/linux/rmap.h
View File

@ -86,6 +86,7 @@ enum ttu_flags {
TTU_MIGRATION = 2, /* migration mode */
TTU_MUNLOCK = 4, /* munlock mode */
TTU_LZFREE = 8, /* lazy free mode */
TTU_SPLIT_HUGE_PMD = 16, /* split huge PMD if any */
TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
@ -93,6 +94,8 @@ enum ttu_flags {
TTU_BATCH_FLUSH = (1 << 11), /* Batch TLB flushes where possible
* and caller guarantees they will
* do a final flush if necessary */
TTU_RMAP_LOCKED = (1 << 12) /* do not grab rmap lock:
* caller holds it */
};
#ifdef CONFIG_MMU

5
mm/huge_memory.c
View File

@ -3006,15 +3006,12 @@ out:
}
}
static void split_huge_pmd_address(struct vm_area_struct *vma,
unsigned long address)
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
pgd = pgd_offset(vma->vm_mm, address);
if (!pgd_present(*pgd))
return;

22
mm/rmap.c
View File

@ -1431,6 +1431,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))
goto out;
if (flags & TTU_SPLIT_HUGE_PMD)
split_huge_pmd_address(vma, address);
pte = page_check_address(page, mm, address, &ptl, 0);
if (!pte)
goto out;
@ -1576,10 +1578,10 @@ static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
return is_vma_temporary_stack(vma);
}
static int page_not_mapped(struct page *page)
static int page_mapcount_is_zero(struct page *page)
{
return !page_mapped(page);
};
return !page_mapcount(page);
}
/**
* try_to_unmap - try to remove all page table mappings to a page
@ -1606,12 +1608,10 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
.arg = &rp,
.done = page_not_mapped,
.done = page_mapcount_is_zero,
.anon_lock = page_lock_anon_vma_read,
};
VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page);
/*
* During exec, a temporary VMA is setup and later moved.
* The VMA is moved under the anon_vma lock but not the
@ -1623,9 +1623,12 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
rwc.invalid_vma = invalid_migration_vma;
if (flags & TTU_RMAP_LOCKED)
ret = rmap_walk_locked(page, &rwc);
else
ret = rmap_walk(page, &rwc);
if (ret != SWAP_MLOCK && !page_mapped(page)) {
if (ret != SWAP_MLOCK && !page_mapcount(page)) {
ret = SWAP_SUCCESS;
if (rp.lazyfreed && !PageDirty(page))
ret = SWAP_LZFREE;
@ -1633,6 +1636,11 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
return ret;
}
static int page_not_mapped(struct page *page)
{
return !page_mapped(page);
};
/**
* try_to_munlock - try to munlock a page
* @page: the page to be munlocked