On Thu, Apr 30, 2015 at 2:43 PM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote: > On Thu, Apr 30, 2015 at 12:02 AM, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >> On Wed, Apr 29, 2015 at 1:44 PM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote: >>> >>> This's no longer true. After recent fixes for "anon_vma endless growing" new vma >>> might reuse old anon_vma from grandparent vma. >> >> Oh well. I guess that was too simple. >> >> If Mark is ok with the rule that "it's not reliably if you have two >> nested forks" (ie it only works if you exec for every fork you do), it >> should still work, right? It sounds like Mark doesn't necessarily need >> to handle the *generic* case. > > What about exposing shared/exclusive bit in pagemap == 1 if > page_mapcount() > 1, otherwise 0 (or vise versa). > > Seems like this should work for detecting CoWed pages in child mm. Something like this (see patch in attachment)
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pagemap-add-mmap-shared-bit-for-marking-pages-mapped-multiple-times
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