77bb499bb6
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. See http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@mail.gmail.com Requested by Mark Williamson. [akpm@linux-foundation.org: fix spello] Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: Mark Williamson <mwilliamson@undo-software.com> Tested-by: Mark Williamson <mwilliamson@undo-software.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| .gitignore | ||
| 00-INDEX | ||
| active_mm.txt | ||
| balance | ||
| cleancache.txt | ||
| frontswap.txt | ||
| highmem.txt | ||
| hugetlbpage.txt | ||
| hwpoison.txt | ||
| ksm.txt | ||
| numa | ||
| numa_memory_policy.txt | ||
| overcommit-accounting | ||
| page_migration | ||
| page_owner.txt | ||
| pagemap.txt | ||
| remap_file_pages.txt | ||
| slub.txt | ||
| soft-dirty.txt | ||
| split_page_table_lock | ||
| transhuge.txt | ||
| unevictable-lru.txt | ||
| userfaultfd.txt | ||
| zsmalloc.txt | ||
| zswap.txt | ||