rmap: extend try_to_unmap() to be usable by split_huge_page()
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>
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a4cecb4..01ad22e 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -106,6 +106,9 @@
__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 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)
{
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index a5875e9..3d975e2 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -86,6 +86,7 @@
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 @@
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
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e1a177c..11d1567 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3006,15 +3006,12 @@
}
}
-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;
diff --git a/mm/rmap.c b/mm/rmap.c
index 30b739c..945933a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1431,6 +1431,8 @@
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 @@
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 @@
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 @@
if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
rwc.invalid_vma = invalid_migration_vma;
- ret = rmap_walk(page, &rwc);
+ 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 @@
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
