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Date: Thu, 30 Apr 2015 15:06:53 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Jerome Marchand <jmarchan@...hat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
Dave Hansen <dave.hansen@...el.com>,
Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
Vlastimil Babka <vbabka@...e.cz>,
Christoph Lameter <cl@...two.org>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Steve Capper <steve.capper@...aro.org>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Sasha Levin <sasha.levin@...cle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv5 20/28] mm: differentiate page_mapped() from
page_mapcount() for compound pages
On Wed, Apr 29, 2015 at 06:20:03PM +0200, Jerome Marchand wrote:
> On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
> > 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@...ux.intel.com>
> > Tested-by: Sasha Levin <sasha.levin@...cle.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 | 11 ++++++++++-
> > mm/filemap.c | 2 +-
> > 11 files changed, 28 insertions(+), 18 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 34b66af516ea..8f972fc8933d 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 dd261df005c2..c4960b2d6682 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 33cb3aa647a6..8ddc184c55d6 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -909,7 +909,16 @@ static inline pgoff_t page_file_index(struct page *page)
> > */
> > static inline int 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;
> > + if (compound_mapcount(page))
> > + return 1;
> > + for (i = 0; i < hpage_nr_pages(page); i++) {
> > + if (atomic_read(&page[i]._mapcount) >= 0)
> > + return 1;
> > + }
> > + return 0;
> > }
>
> page_mapped() won't work with tail pages. Maybe I'm missing something
> that makes it impossible. Otherwise, have you checked that this
> condition is true for all call site? Should we add some check at the
> beginning of the function? Something like:
>
> VM_BUG_ON_PAGE(PageTail(page), page)?
Good catch. I will probably put compound_head() there. Thanks.
--
Kirill A. Shutemov
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