From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> This patch sets bit 56 in pagemap if this page is mapped only once. It allows to detect exclusively used pages without exposing PFN: present file exclusive state 0 0 0 non-present 1 1 0 file page mapped somewhere else 1 1 1 file page mapped only here 1 0 0 anon non-CoWed page (shared with parent/child) 1 0 1 anon CoWed page (or never forked) CoWed pages in MAP_FILE|MAP_PRIVATE areas are anon in this context. Mmap-exclusive bit doesn't reflect potential page-sharing via swapcache: page could be mapped once but has several swap-ptes which point to it. Application could detect that by swap bit in pagemap entry and touch that pte via /proc/pid/mem to get real information. Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@xxxxxxxxxxxxxx --- v2: * handle transparent huge pages * invert bit and rename shared -> exclusive (less confusing name) --- Documentation/vm/pagemap.txt | 3 ++- fs/proc/task_mmu.c | 10 ++++++++++ tools/vm/page-types.c | 12 ++++++++++++ 3 files changed, 24 insertions(+), 1 deletion(-) diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt index 6bfbc17..3cfbbb3 100644 --- a/Documentation/vm/pagemap.txt +++ b/Documentation/vm/pagemap.txt @@ -16,7 +16,8 @@ There are three components to pagemap: * Bits 0-4 swap type if swapped * Bits 5-54 swap offset if swapped * Bit 55 pte is soft-dirty (see Documentation/vm/soft-dirty.txt) - * Bits 56-60 zero + * Bit 56 page exlusively mapped + * Bits 57-60 zero * Bit 61 page is file-page or shared-anon * Bit 62 page swapped * Bit 63 page present diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 21bc251..b02e38f 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -982,6 +982,7 @@ struct pagemapread { #define PM_STATUS2(v2, x) (__PM_PSHIFT(v2 ? x : PAGE_SHIFT)) #define __PM_SOFT_DIRTY (1LL) +#define __PM_MMAP_EXCLUSIVE (2LL) #define PM_PRESENT PM_STATUS(4LL) #define PM_SWAP PM_STATUS(2LL) #define PM_FILE PM_STATUS(1LL) @@ -1074,6 +1075,8 @@ static void pte_to_pagemap_entry(pagemap_entry_t *pme, struct pagemapread *pm, if (page && !PageAnon(page)) flags |= PM_FILE; + if (page && page_mapcount(page) == 1) + flags2 |= __PM_MMAP_EXCLUSIVE; if ((vma->vm_flags & VM_SOFTDIRTY)) flags2 |= __PM_SOFT_DIRTY; @@ -1119,6 +1122,13 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, else pmd_flags2 = 0; + if (pmd_present(*pmd)) { + struct page *page = pmd_page(*pmd); + + if (page_mapcount(page) == 1) + pmd_flags2 |= __PM_MMAP_EXCLUSIVE; + } + for (; addr != end; addr += PAGE_SIZE) { unsigned long offset; pagemap_entry_t pme; diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c index 8bdf16b..3a9f193 100644 --- a/tools/vm/page-types.c +++ b/tools/vm/page-types.c @@ -70,9 +70,12 @@ #define PM_PFRAME(x) ((x) & PM_PFRAME_MASK) #define __PM_SOFT_DIRTY (1LL) +#define __PM_MMAP_EXCLUSIVE (2LL) #define PM_PRESENT PM_STATUS(4LL) #define PM_SWAP PM_STATUS(2LL) +#define PM_FILE PM_STATUS(1LL) #define PM_SOFT_DIRTY __PM_PSHIFT(__PM_SOFT_DIRTY) +#define PM_MMAP_EXCLUSIVE __PM_PSHIFT(__PM_MMAP_EXCLUSIVE) /* @@ -100,6 +103,8 @@ #define KPF_SLOB_FREE 49 #define KPF_SLUB_FROZEN 50 #define KPF_SLUB_DEBUG 51 +#define KPF_FILE 62 +#define KPF_MMAP_EXCLUSIVE 63 #define KPF_ALL_BITS ((uint64_t)~0ULL) #define KPF_HACKERS_BITS (0xffffULL << 32) @@ -149,6 +154,9 @@ static const char * const page_flag_names[] = { [KPF_SLOB_FREE] = "P:slob_free", [KPF_SLUB_FROZEN] = "A:slub_frozen", [KPF_SLUB_DEBUG] = "E:slub_debug", + + [KPF_FILE] = "F:file", + [KPF_MMAP_EXCLUSIVE] = "1:mmap_exclusive", }; @@ -452,6 +460,10 @@ static uint64_t expand_overloaded_flags(uint64_t flags, uint64_t pme) if (pme & PM_SOFT_DIRTY) flags |= BIT(SOFTDIRTY); + if (pme & PM_FILE) + flags |= BIT(FILE); + if (pme & PM_MMAP_EXCLUSIVE) + flags |= BIT(MMAP_EXCLUSIVE); return flags; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>