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> Requested-by: Mark Williamson <mwilliamson@xxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@xxxxxxxxxxxxxx --- Documentation/vm/pagemap.txt | 3 ++- fs/proc/task_mmu.c | 14 +++++++++++++- tools/vm/page-types.c | 10 ++++++++++ 3 files changed, 25 insertions(+), 2 deletions(-) diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt index 6bfbc172cdb9..3cfbbb333ea1 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 3a5d338ea219..bac4c97f8ff8 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -947,6 +947,7 @@ struct pagemapread { #define PM_PFRAME_BITS 55 #define PM_PFRAME_MASK GENMASK_ULL(PM_PFRAME_BITS - 1, 0) #define PM_SOFT_DIRTY BIT_ULL(55) +#define PM_MMAP_EXCLUSIVE BIT_ULL(56) #define PM_FILE BIT_ULL(61) #define PM_SWAP BIT_ULL(62) #define PM_PRESENT BIT_ULL(63) @@ -1034,6 +1035,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm, if (page && !PageAnon(page)) flags |= PM_FILE; + if (page && page_mapcount(page) == 1) + flags |= PM_MMAP_EXCLUSIVE; if (vma->vm_flags & VM_SOFTDIRTY) flags |= PM_SOFT_DIRTY; @@ -1064,6 +1067,11 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, * This if-check is just to prepare for future implementation. */ if (pmd_present(pmd)) { + struct page *page = pmd_page(pmd); + + if (page_mapcount(page) == 1) + flags |= PM_MMAP_EXCLUSIVE; + flags |= PM_PRESENT; if (pm->show_pfn) frame = pmd_pfn(pmd) + @@ -1129,6 +1137,9 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask, if (!PageAnon(page)) flags |= PM_FILE; + if (page_mapcount(page) == 1) + flags |= PM_MMAP_EXCLUSIVE; + flags |= PM_PRESENT; if (pm->show_pfn) frame = pte_pfn(pte) + @@ -1161,7 +1172,8 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask, * 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 exclusively 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/tools/vm/page-types.c b/tools/vm/page-types.c index 603ec916716b..7f73fa32a590 100644 --- a/tools/vm/page-types.c +++ b/tools/vm/page-types.c @@ -62,6 +62,7 @@ #define PM_PFRAME_MASK ((1LL << PM_PFRAME_BITS) - 1) #define PM_PFRAME(x) ((x) & PM_PFRAME_MASK) #define PM_SOFT_DIRTY (1ULL << 55) +#define PM_MMAP_EXCLUSIVE (1ULL << 56) #define PM_FILE (1ULL << 61) #define PM_SWAP (1ULL << 62) #define PM_PRESENT (1ULL << 63) @@ -91,6 +92,8 @@ #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) @@ -140,6 +143,9 @@ 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", }; @@ -443,6 +449,10 @@ 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 from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
