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-rw-r--r--fs/proc/page.c5
-rw-r--r--include/linux/ksm.h29
-rw-r--r--mm/memory.c3
3 files changed, 36 insertions, 1 deletions
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 2707c6c7a20f..2281c2cbfe2b 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -2,6 +2,7 @@
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/init.h>
+#include <linux/ksm.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/proc_fs.h>
@@ -95,6 +96,8 @@ static const struct file_operations proc_kpagecount_operations = {
#define KPF_UNEVICTABLE 18
#define KPF_NOPAGE 20
+#define KPF_KSM 21
+
/* kernel hacking assistances
* WARNING: subject to change, never rely on them!
*/
@@ -137,6 +140,8 @@ static u64 get_uflags(struct page *page)
u |= 1 << KPF_MMAP;
if (PageAnon(page))
u |= 1 << KPF_ANON;
+ if (PageKsm(page))
+ u |= 1 << KPF_KSM;
/*
* compound pages: export both head/tail info
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index eb2a448981ee..a485c14ecd5d 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -10,6 +10,7 @@
#include <linux/bitops.h>
#include <linux/mm.h>
#include <linux/sched.h>
+#include <linux/vmstat.h>
#ifdef CONFIG_KSM
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -29,6 +30,27 @@ static inline void ksm_exit(struct mm_struct *mm)
if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
__ksm_exit(mm);
}
+
+/*
+ * A KSM page is one of those write-protected "shared pages" or "merged pages"
+ * which KSM maps into multiple mms, wherever identical anonymous page content
+ * is found in VM_MERGEABLE vmas. It's a PageAnon page, with NULL anon_vma.
+ */
+static inline int PageKsm(struct page *page)
+{
+ return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
+}
+
+/*
+ * But we have to avoid the checking which page_add_anon_rmap() performs.
+ */
+static inline void page_add_ksm_rmap(struct page *page)
+{
+ if (atomic_inc_and_test(&page->_mapcount)) {
+ page->mapping = (void *) PAGE_MAPPING_ANON;
+ __inc_zone_page_state(page, NR_ANON_PAGES);
+ }
+}
#else /* !CONFIG_KSM */
static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
@@ -45,6 +67,13 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
static inline void ksm_exit(struct mm_struct *mm)
{
}
+
+static inline int PageKsm(struct page *page)
+{
+ return 0;
+}
+
+/* No stub required for page_add_ksm_rmap(page) */
#endif /* !CONFIG_KSM */
#endif
diff --git a/mm/memory.c b/mm/memory.c
index 7a61a11f1867..1a435b81876c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -45,6 +45,7 @@
#include <linux/swap.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
+#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/module.h>
#include <linux/delayacct.h>
@@ -1974,7 +1975,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Take out anonymous pages first, anonymous shared vmas are
* not dirty accountable.
*/
- if (PageAnon(old_page)) {
+ if (PageAnon(old_page) && !PageKsm(old_page)) {
if (!trylock_page(old_page)) {
page_cache_get(old_page);
pte_unmap_unlock(page_table, ptl);