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)
Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru>
Link:
lkml.kernel.org/r/caevpba+_ryackhodzrrvqls80iy0sqpdrd0aap_-tgnx3y9...@mail.gmail.com
---
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 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 6dee68d013ff..29febec65de4 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 8bdf16b8ba60..3a9f193526ee 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;
}
--
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