mlock: count attempts to free mlocked page

Allow free of mlock()ed pages.  This shouldn't happen, but during
developement, it occasionally did.

This patch allows us to survive that condition, while keeping the
statistics and events correct for debug.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Rik van Riel <riel@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/vmstat.h b/include/linux/vmstat.h
index 05b805020be2b63e801861e3f7ad476d6f8b79f7..9cd3ab0f554d301224f518391b47fdd1752fc33d 100644 (file)
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -49,6 +49,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
                UNEVICTABLE_PGMUNLOCKED,
                UNEVICTABLE_PGCLEARED,  /* on COW, page truncate */
                UNEVICTABLE_PGSTRANDED, /* unable to isolate on unlock */
+               UNEVICTABLE_MLOCKFREED,
 #endif
                NR_VM_EVENT_ITEMS
 };

diff --git a/mm/internal.h b/mm/internal.h
index 1cfbf2e2bc9e57e85776f19f1578edf8a70044b1..e4e728bdf324fc62a24ba0c951869989ab081ea1 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -146,6 +146,22 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
        }
 }
 
+/*
+ * free_page_mlock() -- clean up attempts to free and mlocked() page.
+ * Page should not be on lru, so no need to fix that up.
+ * free_pages_check() will verify...
+ */
+static inline void free_page_mlock(struct page *page)
+{
+       if (unlikely(TestClearPageMlocked(page))) {
+               unsigned long flags;
+
+               local_irq_save(flags);
+               __dec_zone_page_state(page, NR_MLOCK);
+               __count_vm_event(UNEVICTABLE_MLOCKFREED);
+               local_irq_restore(flags);
+       }
+}
 
 #else /* CONFIG_UNEVICTABLE_LRU */
 static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
@@ -155,6 +171,7 @@ static inline int is_mlocked_vma(struct vm_area_struct *v, struct page *p)
 static inline void clear_page_mlock(struct page *page) { }
 static inline void mlock_vma_page(struct page *page) { }
 static inline void mlock_migrate_page(struct page *new, struct page *old) { }
+static inline void free_page_mlock(struct page *page) { }
 
 #endif /* CONFIG_UNEVICTABLE_LRU */
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5886586fde6ca7c4971bec788b688128e0206c66..cfbadad75d1d01f4a3aa2d180f82f95517322cc8 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -454,6 +454,7 @@ static inline void __free_one_page(struct page *page,
 
 static inline int free_pages_check(struct page *page)
 {
+       free_page_mlock(page);
        if (unlikely(page_mapcount(page) |
                (page->mapping != NULL)  |
                (page_get_page_cgroup(page) != NULL) |

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 9e28abc0a0b905c7926325df01722a6d1c2ae4fa..9343227c5c60b6dc3a1b7e09c64143a53a407003 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -689,6 +689,7 @@ static const char * const vmstat_text[] = {
        "unevictable_pgs_munlocked",
        "unevictable_pgs_cleared",
        "unevictable_pgs_stranded",
+       "unevictable_pgs_mlockfreed",
 #endif
 #endif
 };