From: Huang Ying <ying.hu...@intel.com>

>From commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB
trunks") on, after swapoff, the address_space associated with the swap
device will be freed.  So page_mapping() users which may touch the
address_space need some kind of mechanism to prevent the address_space
from being freed during accessing.

The dcache flushing functions (flush_dcache_page(), etc) in
architecture specific code may access the address_space of swap device
for anonymous pages in swap cache via page_mapping() function.  But in
some cases there are no mechanisms to prevent the swap device from
being swapoff, for example,

CPU1                                    CPU2
__get_user_pages()                      swapoff()
  flush_dcache_page()
    mapping = page_mapping()
      ...                                 exit_swap_address_space()
      ...                                   kvfree(spaces)
      mapping_mapped(mapping)

The address space may be accessed after being freed.

But from cachetlb.txt and Russell King, flush_dcache_page() only care
about file cache pages, for anonymous pages, flush_anon_page() should
be used.  The implementation of flush_dcache_page() in all
architectures follows this too.  They will check whether
page_mapping() is NULL and whether mapping_mapped() is true to
determine whether to flush the dcache immediately.  And they will use
interval tree (mapping->i_mmap) to find all user space mappings.
While mapping_mapped() and mapping->i_mmap isn't used by anonymous
pages in swap cache at all.

So, to fix the race between swapoff and flush dcache, __page_mapping()
is add to return the address_space for file cache pages and NULL
otherwise.  All page_mapping() invoking in flush dcache functions are
replaced with __page_mapping().

The patch is only build tested, because I have no machine with
architecture other than x86.

Signed-off-by: "Huang, Ying" <ying.hu...@intel.com>
Cc: Minchan Kim <minc...@kernel.org>
Cc: Michal Hocko <mho...@suse.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Mel Gorman <mgor...@techsingularity.net>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: Chen Liqin <liqin.li...@gmail.com>
Cc: Russell King <li...@armlinux.org.uk>
Cc: Yoshinori Sato <ys...@users.sourceforge.jp>
Cc: "James E.J. Bottomley" <j...@parisc-linux.org>
Cc: Guan Xuetao <g...@mprc.pku.edu.cn>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Chris Zankel <ch...@zankel.net>
Cc: Vineet Gupta <vgu...@synopsys.com>
Cc: Ley Foon Tan <lf...@altera.com>
Cc: Ralf Baechle <r...@linux-mips.org>
Cc: Andi Kleen <a...@linux.intel.com>
---
 arch/arc/mm/cache.c           |  2 +-
 arch/arm/mm/copypage-v4mc.c   |  2 +-
 arch/arm/mm/copypage-v6.c     |  2 +-
 arch/arm/mm/copypage-xscale.c |  2 +-
 arch/arm/mm/fault-armv.c      |  2 +-
 arch/arm/mm/flush.c           |  6 +++---
 arch/mips/mm/cache.c          |  2 +-
 arch/nios2/mm/cacheflush.c    |  4 ++--
 arch/parisc/kernel/cache.c    |  4 ++--
 arch/score/mm/cache.c         |  4 ++--
 arch/sh/mm/cache-sh4.c        |  2 +-
 arch/sh/mm/cache-sh7705.c     |  2 +-
 arch/sparc/kernel/smp_64.c    |  8 ++++----
 arch/sparc/mm/init_64.c       |  6 +++---
 arch/sparc/mm/tlb.c           |  2 +-
 arch/unicore32/mm/flush.c     |  2 +-
 arch/unicore32/mm/mmu.c       |  2 +-
 arch/xtensa/mm/cache.c        |  2 +-
 include/linux/mm.h            |  1 +
 mm/util.c                     | 20 ++++++++++++++++++++
 20 files changed, 49 insertions(+), 28 deletions(-)

diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 2072f3451e9c..0f607d5a85da 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -833,7 +833,7 @@ void flush_dcache_page(struct page *page)
        }
 
        /* don't handle anon pages here */
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
        if (!mapping)
                return;
 
diff --git a/arch/arm/mm/copypage-v4mc.c b/arch/arm/mm/copypage-v4mc.c
index 1267e64133b9..6d9e632ca43b 100644
--- a/arch/arm/mm/copypage-v4mc.c
+++ b/arch/arm/mm/copypage-v4mc.c
@@ -70,7 +70,7 @@ void v4_mc_copy_user_highpage(struct page *to, struct page 
*from,
        void *kto = kmap_atomic(to);
 
        if (!test_and_set_bit(PG_dcache_clean, &from->flags))
-               __flush_dcache_page(page_mapping(from), from);
+               __flush_dcache_page(__page_mapping(from), from);
 
        raw_spin_lock(&minicache_lock);
 
diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
index 70423345da26..2f13ffd847a6 100644
--- a/arch/arm/mm/copypage-v6.c
+++ b/arch/arm/mm/copypage-v6.c
@@ -76,7 +76,7 @@ static void v6_copy_user_highpage_aliasing(struct page *to,
        unsigned long kfrom, kto;
 
        if (!test_and_set_bit(PG_dcache_clean, &from->flags))
-               __flush_dcache_page(page_mapping(from), from);
+               __flush_dcache_page(__page_mapping(from), from);
 
        /* FIXME: not highmem safe */
        discard_old_kernel_data(page_address(to));
diff --git a/arch/arm/mm/copypage-xscale.c b/arch/arm/mm/copypage-xscale.c
index 0fb85025344d..221129649627 100644
--- a/arch/arm/mm/copypage-xscale.c
+++ b/arch/arm/mm/copypage-xscale.c
@@ -90,7 +90,7 @@ void xscale_mc_copy_user_highpage(struct page *to, struct 
page *from,
        void *kto = kmap_atomic(to);
 
        if (!test_and_set_bit(PG_dcache_clean, &from->flags))
-               __flush_dcache_page(page_mapping(from), from);
+               __flush_dcache_page(__page_mapping(from), from);
 
        raw_spin_lock(&minicache_lock);
 
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index d9e0d00a6699..593bd1549ce0 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c
@@ -195,7 +195,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned 
long addr,
        if (page == ZERO_PAGE(0))
                return;
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
        if (!test_and_set_bit(PG_dcache_clean, &page->flags))
                __flush_dcache_page(mapping, page);
        if (mapping) {
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index f1e6190aa7ea..2e4a478c6f02 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -285,7 +285,7 @@ void __sync_icache_dcache(pte_t pteval)
 
        page = pfn_to_page(pfn);
        if (cache_is_vipt_aliasing())
-               mapping = page_mapping(page);
+               mapping = __page_mapping(page);
        else
                mapping = NULL;
 
@@ -333,7 +333,7 @@ void flush_dcache_page(struct page *page)
                return;
        }
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
 
        if (!cache_ops_need_broadcast() &&
            mapping && !page_mapcount(page))
@@ -363,7 +363,7 @@ void flush_kernel_dcache_page(struct page *page)
        if (cache_is_vivt() || cache_is_vipt_aliasing()) {
                struct address_space *mapping;
 
-               mapping = page_mapping(page);
+               mapping = __page_mapping(page);
 
                if (!mapping || mapping_mapped(mapping)) {
                        void *addr;
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 44ac64d51827..8a21c0345516 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -86,7 +86,7 @@ SYSCALL_DEFINE3(cacheflush, unsigned long, addr, unsigned 
long, bytes,
 
 void __flush_dcache_page(struct page *page)
 {
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
        unsigned long addr;
 
        if (mapping && !mapping_mapped(mapping)) {
diff --git a/arch/nios2/mm/cacheflush.c b/arch/nios2/mm/cacheflush.c
index 87bf88ed04c6..117bece3eb80 100644
--- a/arch/nios2/mm/cacheflush.c
+++ b/arch/nios2/mm/cacheflush.c
@@ -180,7 +180,7 @@ void flush_dcache_page(struct page *page)
        if (page == ZERO_PAGE(0))
                return;
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
 
        /* Flush this page if there are aliases. */
        if (mapping && !mapping_mapped(mapping)) {
@@ -215,7 +215,7 @@ void update_mmu_cache(struct vm_area_struct *vma,
        if (page == ZERO_PAGE(0))
                return;
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
        if (!test_and_set_bit(PG_dcache_clean, &page->flags))
                __flush_dcache_page(mapping, page);
 
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 7c1bde80ada4..2150dd193654 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -88,7 +88,7 @@ update_mmu_cache(struct vm_area_struct *vma, unsigned long 
address, pte_t *ptep)
                return;
 
        page = pfn_to_page(pfn);
-       if (page_mapping(page) && test_bit(PG_dcache_dirty, &page->flags)) {
+       if (__page_mapping(page) && test_bit(PG_dcache_dirty, &page->flags)) {
                flush_kernel_dcache_page_addr(pfn_va(pfn));
                clear_bit(PG_dcache_dirty, &page->flags);
        } else if (parisc_requires_coherency())
@@ -304,7 +304,7 @@ __flush_cache_page(struct vm_area_struct *vma, unsigned 
long vmaddr,
 
 void flush_dcache_page(struct page *page)
 {
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
        struct vm_area_struct *mpnt;
        unsigned long offset;
        unsigned long addr, old_addr = 0;
diff --git a/arch/score/mm/cache.c b/arch/score/mm/cache.c
index b4bcfd3e8393..a74967a396e6 100644
--- a/arch/score/mm/cache.c
+++ b/arch/score/mm/cache.c
@@ -54,7 +54,7 @@ static void flush_data_cache_page(unsigned long addr)
 
 void flush_dcache_page(struct page *page)
 {
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
        unsigned long addr;
 
        if (PageHighMem(page))
@@ -86,7 +86,7 @@ void __update_cache(struct vm_area_struct *vma, unsigned long 
address,
        if (unlikely(!pfn_valid(pfn)))
                return;
        page = pfn_to_page(pfn);
-       if (page_mapping(page) && test_bit(PG_dcache_dirty, &(page)->flags)) {
+       if (__page_mapping(page) && test_bit(PG_dcache_dirty, &(page)->flags)) {
                addr = (unsigned long) page_address(page);
                if (exec)
                        flush_data_cache_page(addr);
diff --git a/arch/sh/mm/cache-sh4.c b/arch/sh/mm/cache-sh4.c
index 58aaa4f33b81..281e33daaa98 100644
--- a/arch/sh/mm/cache-sh4.c
+++ b/arch/sh/mm/cache-sh4.c
@@ -112,7 +112,7 @@ static void sh4_flush_dcache_page(void *arg)
        struct page *page = arg;
        unsigned long addr = (unsigned long)page_address(page);
 #ifndef CONFIG_SMP
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
 
        if (mapping && !mapping_mapped(mapping))
                clear_bit(PG_dcache_clean, &page->flags);
diff --git a/arch/sh/mm/cache-sh7705.c b/arch/sh/mm/cache-sh7705.c
index 6cd2aa395817..92db57ccc35a 100644
--- a/arch/sh/mm/cache-sh7705.c
+++ b/arch/sh/mm/cache-sh7705.c
@@ -136,7 +136,7 @@ static void __flush_dcache_page(unsigned long phys)
 static void sh7705_flush_dcache_page(void *arg)
 {
        struct page *page = arg;
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
 
        if (mapping && !mapping_mapped(mapping))
                clear_bit(PG_dcache_clean, &page->flags);
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index c50182cd2f64..5bd8b67e66f2 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -929,9 +929,9 @@ static inline void __local_flush_dcache_page(struct page 
*page)
 #ifdef DCACHE_ALIASING_POSSIBLE
        __flush_dcache_page(page_address(page),
                            ((tlb_type == spitfire) &&
-                            page_mapping(page) != NULL));
+                            __page_mapping(page) != NULL));
 #else
-       if (page_mapping(page) != NULL &&
+       if (__page_mapping(page) != NULL &&
            tlb_type == spitfire)
                __flush_icache_page(__pa(page_address(page)));
 #endif
@@ -958,7 +958,7 @@ void smp_flush_dcache_page_impl(struct page *page, int cpu)
 
                if (tlb_type == spitfire) {
                        data0 = ((u64)&xcall_flush_dcache_page_spitfire);
-                       if (page_mapping(page) != NULL)
+                       if (__page_mapping(page) != NULL)
                                data0 |= ((u64)1 << 32);
                } else if (tlb_type == cheetah || tlb_type == cheetah_plus) {
 #ifdef DCACHE_ALIASING_POSSIBLE
@@ -994,7 +994,7 @@ void flush_dcache_page_all(struct mm_struct *mm, struct 
page *page)
        pg_addr = page_address(page);
        if (tlb_type == spitfire) {
                data0 = ((u64)&xcall_flush_dcache_page_spitfire);
-               if (page_mapping(page) != NULL)
+               if (__page_mapping(page) != NULL)
                        data0 |= ((u64)1 << 32);
        } else if (tlb_type == cheetah || tlb_type == cheetah_plus) {
 #ifdef DCACHE_ALIASING_POSSIBLE
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index a9f94e911e0a..6f0f3f2b04a9 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -206,9 +206,9 @@ inline void flush_dcache_page_impl(struct page *page)
 #ifdef DCACHE_ALIASING_POSSIBLE
        __flush_dcache_page(page_address(page),
                            ((tlb_type == spitfire) &&
-                            page_mapping(page) != NULL));
+                            __page_mapping(page) != NULL));
 #else
-       if (page_mapping(page) != NULL &&
+       if (__page_mapping(page) != NULL &&
            tlb_type == spitfire)
                __flush_icache_page(__pa(page_address(page)));
 #endif
@@ -490,7 +490,7 @@ void flush_dcache_page(struct page *page)
 
        this_cpu = get_cpu();
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
        if (mapping && !mapping_mapped(mapping)) {
                int dirty = test_bit(PG_dcache_dirty, &page->flags);
                if (dirty) {
diff --git a/arch/sparc/mm/tlb.c b/arch/sparc/mm/tlb.c
index 847ddffbf38a..5d7c13b88a42 100644
--- a/arch/sparc/mm/tlb.c
+++ b/arch/sparc/mm/tlb.c
@@ -128,7 +128,7 @@ void tlb_batch_add(struct mm_struct *mm, unsigned long 
vaddr,
                        goto no_cache_flush;
 
                /* A real file page? */
-               mapping = page_mapping(page);
+               mapping = __page_mapping(page);
                if (!mapping)
                        goto no_cache_flush;
 
diff --git a/arch/unicore32/mm/flush.c b/arch/unicore32/mm/flush.c
index 6d4c096ffa2a..def5142d16ea 100644
--- a/arch/unicore32/mm/flush.c
+++ b/arch/unicore32/mm/flush.c
@@ -83,7 +83,7 @@ void flush_dcache_page(struct page *page)
        if (page == ZERO_PAGE(0))
                return;
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
 
        if (mapping && !mapping_mapped(mapping))
                clear_bit(PG_dcache_clean, &page->flags);
diff --git a/arch/unicore32/mm/mmu.c b/arch/unicore32/mm/mmu.c
index 4f5a532bee13..2bd143b7aca3 100644
--- a/arch/unicore32/mm/mmu.c
+++ b/arch/unicore32/mm/mmu.c
@@ -503,7 +503,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned 
long addr,
        if (page == ZERO_PAGE(0))
                return;
 
-       mapping = page_mapping(page);
+       mapping = __page_mapping(page);
        if (!test_and_set_bit(PG_dcache_clean, &page->flags))
                __flush_dcache_page(mapping, page);
        if (mapping)
diff --git a/arch/xtensa/mm/cache.c b/arch/xtensa/mm/cache.c
index 57dc231a0709..17485819d03b 100644
--- a/arch/xtensa/mm/cache.c
+++ b/arch/xtensa/mm/cache.c
@@ -127,7 +127,7 @@ EXPORT_SYMBOL(copy_user_highpage);
 
 void flush_dcache_page(struct page *page)
 {
-       struct address_space *mapping = page_mapping(page);
+       struct address_space *mapping = __page_mapping(page);
 
        /*
         * If we have a mapping but the page is not mapped to user-space
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c500bdfadf79..16d5e27b4438 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1146,6 +1146,7 @@ static inline pgoff_t page_index(struct page *page)
 }
 
 bool page_mapped(struct page *page);
+struct address_space *__page_mapping(struct page *page);
 struct address_space *page_mapping(struct page *page);
 
 /*
diff --git a/mm/util.c b/mm/util.c
index d800ce40816c..f47f3a1cc3f2 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -490,6 +490,26 @@ struct anon_vma *page_anon_vma(struct page *page)
        return __page_rmapping(page);
 }
 
+/*
+ * For file cache pages, return the address_space, otherwise return NULL
+ */
+struct address_space *__page_mapping(struct page *page)
+{
+       struct address_space *mapping;
+
+       page = compound_head(page);
+
+       /* This happens if someone calls flush_dcache_page on slab page */
+       if (unlikely(PageSlab(page)))
+               return NULL;
+
+       mapping = page->mapping;
+       if ((unsigned long)mapping & PAGE_MAPPING_ANON)
+               return NULL;
+
+       return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
+}
+
 struct address_space *page_mapping(struct page *page)
 {
        struct address_space *mapping;
-- 
2.15.1

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