Re: [PATCHv6 27/36] mm: differentiate page_mapped() from page_mapcount() for compound pages

Kirill A. Shutemov
2015-06-09T11:00:26Z

On Wed, Jun 03, 2015 at 08:05:58PM +0300, Kirill A. Shutemov wrote:
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 22cd540104ec..16add6692f49 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -917,10 +917,21 @@ static inline pgoff_t page_file_index(struct page *page)
>
> /*
> * Return true if this page is mapped into pagetables.
> + * For compound page it returns true if any subpage of compound page is mapped.
> */
> -static inline int page_mapped(struct page *page)
> +static inline bool page_mapped(struct page *page)
> {
> - return atomic_read(&(page)->_mapcount) + compound_mapcount(page) >= 0;
> + int i;
> + if (likely(!PageCompound(page)))
> + return atomic_read(&page->_mapcount) >= 0;
> + page = compound_head(page);
> + if (compound_mapcount(page))
> + return true;
> + for (i = 0; i < hpage_nr_pages(page); i++) {
> + if (atomic_read(&page[i]._mapcount) >= 0)
> + return true;
> + }
> + return true;

Oops. 'false' should be here. Updated patch is below.

>From f0a84566f1a3d2545a3e557f93a668ecba0c842d Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Fri, 20 Mar 2015 12:24:55 +0200
Subject: [PATCH] mm: differentiate page_mapped() from page_mapcount() for
compound pages

Let's define page_mapped() to be true for compound pages if any
sub-pages of the compound page is mapped (with PMD or PTE).

On other hand page_mapcount() return mapcount for this particular small
page.

This will make cases like page_get_anon_vma() behave correctly once we
allow huge pages to be mapped with PTE.

Most users outside core-mm should use page_mapcount() instead of
page_mapped().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
---
arch/arc/mm/cache_arc700.c | 4 ++--
arch/arm/mm/flush.c | 2 +-
arch/mips/mm/c-r4k.c | 3 ++-
arch/mips/mm/cache.c | 2 +-
arch/mips/mm/init.c | 6 +++---
arch/sh/mm/cache-sh4.c | 2 +-
arch/sh/mm/cache.c | 8 ++++----
arch/xtensa/mm/tlb.c | 2 +-
fs/proc/page.c | 4 ++--
include/linux/mm.h | 15 +++++++++++++--
mm/filemap.c | 2 +-
11 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/arch/arc/mm/cache_arc700.c b/arch/arc/mm/cache_arc700.c
index 8c3a3e02ba92..1baa4d23314b 100644
--- a/arch/arc/mm/cache_arc700.c
+++ b/arch/arc/mm/cache_arc700.c
@@ -490,7 +490,7 @@ void flush_dcache_page(struct page *page)
*/
if (!mapping_mapped(mapping)) {
clear_bit(PG_dc_clean, &page->flags);
- } else if (page_mapped(page)) {
+ } else if (page_mapcount(page)) {

/* kernel reading from page with U-mapping */
void *paddr = page_address(page);
@@ -675,7 +675,7 @@ void copy_user_highpage(struct page *to, struct page *from,
* Note that while @u_vaddr refers to DST page's userspace vaddr, it is
* equally valid for SRC page as well
*/
- if (page_mapped(from) && addr_not_cache_congruent(kfrom, u_vaddr)) {
+ if (page_mapcount(from) && addr_not_cache_congruent(kfrom, u_vaddr)) {
__flush_dcache_page(kfrom, u_vaddr);
clean_src_k_mappings = 1;
}
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 77f229302032..4da544aa25ef 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -315,7 +315,7 @@ void flush_dcache_page(struct page *page)
mapping = page_mapping(page);

if (!cache_ops_need_broadcast() &&
- mapping && !page_mapped(page))
+ mapping && !page_mapcount(page))
clear_bit(PG_dcache_clean, &page->flags);
else {
__flush_dcache_page(mapping, page);
diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 3f8059602765..b28bf185ef77 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -578,7 +578,8 @@ static inline void local_r4k_flush_cache_page(void *args)
* another ASID than the current one.
*/
map_coherent = (cpu_has_dc_aliases &&
- page_mapped(page) && !Page_dcache_dirty(page));
+ page_mapcount(page) &&
+ !Page_dcache_dirty(page));
if (map_coherent)
vaddr = kmap_coherent(page, addr);
else
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 7e3ea7766822..e695b28dc32c 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -106,7 +106,7 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
unsigned long addr = (unsigned long) page_address(page);

if (pages_do_alias(addr, vmaddr)) {
- if (page_mapped(page) && !Page_dcache_dirty(page)) {
+ if (page_mapcount(page) && !Page_dcache_dirty(page)) {
void *kaddr;

kaddr = kmap_coherent(page, vmaddr);
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 448cde372af0..2c8e44aa536e 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -156,7 +156,7 @@ void copy_user_highpage(struct page *to, struct page *from,

vto = kmap_atomic(to);
if (cpu_has_dc_aliases &&
- page_mapped(from) && !Page_dcache_dirty(from)) {
+ page_mapcount(from) && !Page_dcache_dirty(from)) {
vfrom = kmap_coherent(from, vaddr);
copy_page(vto, vfrom);
kunmap_coherent();
@@ -178,7 +178,7 @@ void copy_to_user_page(struct vm_area_struct *vma,
unsigned long len)
{
if (cpu_has_dc_aliases &&
- page_mapped(page) && !Page_dcache_dirty(page)) {
+ page_mapcount(page) && !Page_dcache_dirty(page)) {
void *vto = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(vto, src, len);
kunmap_coherent();
@@ -196,7 +196,7 @@ void copy_from_user_page(struct vm_area_struct *vma,
unsigned long len)
{
if (cpu_has_dc_aliases &&
- page_mapped(page) && !Page_dcache_dirty(page)) {
+ page_mapcount(page) && !Page_dcache_dirty(page)) {
void *vfrom = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(dst, vfrom, len);
kunmap_coherent();
diff --git a/arch/sh/mm/cache-sh4.c b/arch/sh/mm/cache-sh4.c
index 51d8f7f31d1d..58aaa4f33b81 100644
--- a/arch/sh/mm/cache-sh4.c
+++ b/arch/sh/mm/cache-sh4.c
@@ -241,7 +241,7 @@ static void sh4_flush_cache_page(void *args)
*/
map_coherent = (current_cpu_data.dcache.n_aliases &&
test_bit(PG_dcache_clean, &page->flags) &&
- page_mapped(page));
+ page_mapcount(page));
if (map_coherent)
vaddr = kmap_coherent(page, address);
else
diff --git a/arch/sh/mm/cache.c b/arch/sh/mm/cache.c
index f770e3992620..e58cfbf45150 100644
--- a/arch/sh/mm/cache.c
+++ b/arch/sh/mm/cache.c
@@ -59,7 +59,7 @@ void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
- if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+ if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
test_bit(PG_dcache_clean, &page->flags)) {
void *vto = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(vto, src, len);
@@ -78,7 +78,7 @@ void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
unsigned long vaddr, void *dst, const void *src,
unsigned long len)
{
- if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+ if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
test_bit(PG_dcache_clean, &page->flags)) {
void *vfrom = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
memcpy(dst, vfrom, len);
@@ -97,7 +97,7 @@ void copy_user_highpage(struct page *to, struct page *from,

vto = kmap_atomic(to);

- if (boot_cpu_data.dcache.n_aliases && page_mapped(from) &&
+ if (boot_cpu_data.dcache.n_aliases && page_mapcount(from) &&
test_bit(PG_dcache_clean, &from->flags)) {
vfrom = kmap_coherent(from, vaddr);
copy_page(vto, vfrom);
@@ -153,7 +153,7 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
unsigned long addr = (unsigned long) page_address(page);

if (pages_do_alias(addr, vmaddr)) {
- if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+ if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
test_bit(PG_dcache_clean, &page->flags)) {
void *kaddr;

diff --git a/arch/xtensa/mm/tlb.c b/arch/xtensa/mm/tlb.c
index 5ece856c5725..35c822286bbe 100644
--- a/arch/xtensa/mm/tlb.c
+++ b/arch/xtensa/mm/tlb.c
@@ -245,7 +245,7 @@ static int check_tlb_entry(unsigned w, unsigned e, bool dtlb)
page_mapcount(p));
if (!page_count(p))
rc |= TLB_INSANE;
- else if (page_mapped(p))
+ else if (page_mapcount(p))
rc |= TLB_SUSPICIOUS;
} else {
rc |= TLB_INSANE;
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 7eee2d8b97d9..e99c059339f6 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -97,9 +97,9 @@ u64 stable_page_flags(struct page *page)
* pseudo flags for the well known (anonymous) memory mapped pages
*
* Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
- * simple test in page_mapped() is not enough.
+ * simple test in page_mapcount() is not enough.
*/
- if (!PageSlab(page) && page_mapped(page))
+ if (!PageSlab(page) && page_mapcount(page))
u |= 1 << KPF_MMAP;
if (PageAnon(page))
u |= 1 << KPF_ANON;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 22cd540104ec..8cd6ee853eee 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -917,10 +917,21 @@ static inline pgoff_t page_file_index(struct page *page)

/*
* Return true if this page is mapped into pagetables.
+ * For compound page it returns true if any subpage of compound page is mapped.
*/
-static inline int page_mapped(struct page *page)
+static inline bool page_mapped(struct page *page)
{
- return atomic_read(&(page)->_mapcount) + compound_mapcount(page) >= 0;
+ int i;
+ if (likely(!PageCompound(page)))
+ return atomic_read(&page->_mapcount) >= 0;
+ page = compound_head(page);
+ if (compound_mapcount(page))
+ return true;
+ for (i = 0; i < hpage_nr_pages(page); i++) {
+ if (atomic_read(&page[i]._mapcount) >= 0)
+ return true;
+ }
+ return false;
}

/*
diff --git a/mm/filemap.c b/mm/filemap.c
index fb0ba54c3ac5..c5a40dd4f846 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -202,7 +202,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
__dec_zone_page_state(page, NR_FILE_PAGES);
if (PageSwapBacked(page))
__dec_zone_page_state(page, NR_SHMEM);
- BUG_ON(page_mapped(page));
+ VM_BUG_ON_PAGE(page_mapped(page), page);

/*
* At this point page must be either written or cleaned by truncate.
--
Kirill A. Shutemov