On Tue, Jul 14, 2015 at 06:37:49PM +0300, Konstantin Khlebnikov wrote: > 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 <[email protected]> > Requested-by: Mark Williamson <[email protected]> > Link: > http://lkml.kernel.org/r/caevpba+_ryackhodzrrvqls80iy0sqpdrd0aap_-tgnx3y9...@mail.gmail.com
Reviewed-by: Naoya Horiguchi <[email protected]>-- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
