The patch titled
mm: define PAGE_MAPPING_FLAGS
has been added to the -mm tree. Its filename is
mm-define-page_mapping_flags.patch
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------------------------------------------------------
Subject: mm: define PAGE_MAPPING_FLAGS
From: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set
in page->mapping, with the higher bits a pointer to the anon_vma; and have
defined PageKsm(page) as that with NULL anon_vma.
But KSM swapping will need to store a pointer there: so in preparation for
that, now define PAGE_MAPPING_FLAGS as the low two bits, including
PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some
other use for the bit emerges).
Declare page_rmapping(page) to return the pointer part of page->mapping,
and page_anon_vma(page) to return the anon_vma pointer when that's what it
is. Use these in a few appropriate places: notably, unuse_vma() has been
testing page->mapping, but is better to be testing page_anon_vma() (cases
may be added in which flag bits are set without any pointer).
Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Cc: Izik Eidus <ieidus@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/ksm.h | 5 +++--
include/linux/mm.h | 17 ++++++++++++++++-
include/linux/rmap.h | 8 ++++++++
mm/migrate.c | 11 ++++-------
mm/rmap.c | 7 +++----
mm/swapfile.c | 2 +-
6 files changed, 35 insertions(+), 15 deletions(-)
diff -puN include/linux/ksm.h~mm-define-page_mapping_flags include/linux/ksm.h
--- a/include/linux/ksm.h~mm-define-page_mapping_flags
+++ a/include/linux/ksm.h
@@ -38,7 +38,8 @@ static inline void ksm_exit(struct mm_st
*/
static inline int PageKsm(struct page *page)
{
- return ((unsigned long)page->mapping == PAGE_MAPPING_ANON);
+ return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
+ (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
}
/*
@@ -47,7 +48,7 @@ static inline int PageKsm(struct page *p
static inline void page_add_ksm_rmap(struct page *page)
{
if (atomic_inc_and_test(&page->_mapcount)) {
- page->mapping = (void *) PAGE_MAPPING_ANON;
+ page->mapping = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
__inc_zone_page_state(page, NR_ANON_PAGES);
}
}
diff -puN include/linux/mm.h~mm-define-page_mapping_flags include/linux/mm.h
--- a/include/linux/mm.h~mm-define-page_mapping_flags
+++ a/include/linux/mm.h
@@ -620,13 +620,22 @@ void page_address_init(void);
/*
* On an anonymous page mapped into a user virtual memory area,
* page->mapping points to its anon_vma, not to a struct address_space;
- * with the PAGE_MAPPING_ANON bit set to distinguish it.
+ * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
+ *
+ * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
+ * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
+ * and then page->mapping points, not to an anon_vma, but to a private
+ * structure which KSM associates with that merged page. See ksm.h.
+ *
+ * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
*
* Please note that, confusingly, "page_mapping" refers to the inode
* address_space which maps the page from disk; whereas "page_mapped"
* refers to user virtual address space into which the page is mapped.
*/
#define PAGE_MAPPING_ANON 1
+#define PAGE_MAPPING_KSM 2
+#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
extern struct address_space swapper_space;
static inline struct address_space *page_mapping(struct page *page)
@@ -644,6 +653,12 @@ static inline struct address_space *page
return mapping;
}
+/* Neutral page->mapping pointer to address_space or anon_vma or other */
+static inline void *page_rmapping(struct page *page)
+{
+ return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
+}
+
static inline int PageAnon(struct page *page)
{
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
diff -puN include/linux/rmap.h~mm-define-page_mapping_flags include/linux/rmap.h
--- a/include/linux/rmap.h~mm-define-page_mapping_flags
+++ a/include/linux/rmap.h
@@ -39,6 +39,14 @@ struct anon_vma {
#ifdef CONFIG_MMU
+static inline struct anon_vma *page_anon_vma(struct page *page)
+{
+ if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
+ PAGE_MAPPING_ANON)
+ return NULL;
+ return page_rmapping(page);
+}
+
static inline void anon_vma_lock(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
diff -puN mm/migrate.c~mm-define-page_mapping_flags mm/migrate.c
--- a/mm/migrate.c~mm-define-page_mapping_flags
+++ a/mm/migrate.c
@@ -172,17 +172,14 @@ static void remove_anon_migration_ptes(s
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
- unsigned long mapping;
-
- mapping = (unsigned long)new->mapping;
-
- if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
- return;
/*
* We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
*/
- anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
+ anon_vma = page_anon_vma(new);
+ if (!anon_vma)
+ return;
+
spin_lock(&anon_vma->lock);
list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
diff -puN mm/rmap.c~mm-define-page_mapping_flags mm/rmap.c
--- a/mm/rmap.c~mm-define-page_mapping_flags
+++ a/mm/rmap.c
@@ -203,7 +203,7 @@ struct anon_vma *page_lock_anon_vma(stru
rcu_read_lock();
anon_mapping = (unsigned long) page->mapping;
- if (!(anon_mapping & PAGE_MAPPING_ANON))
+ if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
goto out;
if (!page_mapped(page))
goto out;
@@ -248,8 +248,7 @@ vma_address(struct page *page, struct vm
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
if (PageAnon(page)) {
- if ((void *)vma->anon_vma !=
- (void *)page->mapping - PAGE_MAPPING_ANON)
+ if (vma->anon_vma != page_anon_vma(page))
return -EFAULT;
} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
if (!vma->vm_file ||
@@ -513,7 +512,7 @@ int page_referenced(struct page *page,
referenced++;
*vm_flags = 0;
- if (page_mapped(page) && page->mapping) {
+ if (page_mapped(page) && page_rmapping(page)) {
if (PageAnon(page))
referenced += page_referenced_anon(page, mem_cont,
vm_flags);
diff -puN mm/swapfile.c~mm-define-page_mapping_flags mm/swapfile.c
--- a/mm/swapfile.c~mm-define-page_mapping_flags
+++ a/mm/swapfile.c
@@ -937,7 +937,7 @@ static int unuse_vma(struct vm_area_stru
unsigned long addr, end, next;
int ret;
- if (page->mapping) {
+ if (page_anon_vma(page)) {
addr = page_address_in_vma(page, vma);
if (addr == -EFAULT)
return 0;
_
Patches currently in -mm which might be from hugh.dickins@xxxxxxxxxxxxx are
origin.patch
mmap-dont-return-enomem-when-mapcount-is-temporarily-exceeded-in-munmap.patch
mmap-dont-return-enomem-when-mapcount-is-temporarily-exceeded-in-munmap-checkpatch-fixes.patch
vmalloc-adjust-gfp-mask-passed-on-nested-vmalloc-invocation.patch
swap_info-private-to-swapfilec.patch
swap_info-change-to-array-of-pointers.patch
swap_info-include-first_swap_extent.patch
swap_info-include-first_swap_extent-fix.patch
swap_info-include-first_swap_extent-fix-fix.patch
swap_info-miscellaneous-minor-cleanups.patch
swap_info-swap_has_cache-cleanups.patch
swap_info-swap_map-of-chars-not-shorts.patch
swap_info-swap-count-continuations.patch
swap_info-note-swap_map_shmem.patch
swap_info-reorder-its-fields.patch
rmap-fix-the-comment-for-try_to_unmap_anon.patch
oom_kill-use-rss-value-instead-of-vm-size-for-badness.patch
mm-define-page_mapping_flags.patch
mm-mlocking-in-try_to_unmap_one.patch
mm-config_mmu-for-pg_mlocked.patch
mm-pass-address-down-to-rmap-ones.patch
mm-stop-ptlock-enlarging-struct-page.patch
mm-sigbus-instead-of-abusing-oom.patch
elf-kill-use_elf_core_dump.patch
prio_tree-debugging-patch.patch
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