On Tue, Mar 08, 2011 at 01:58:30PM +0100, Andrea Arcangeli wrote: > When vmscan.c calls page_referenced, if an anon page was created before a > process forked, rmap will search for it in both of the processes, even though > one of them might have since broken COW. If the child process mlocks the vma > where the COWed page belongs to, page_referenced() running on the page mapped > by the parent would lead to *vm_flags getting VM_LOCKED set erroneously (leading > to the references on the parent page being ignored and evicting the parent page > too early). > > *mapcount would also be decremented by page_referenced_one even if the page > wasn't found by page_check_address. > > This also let pmdp_clear_flush_young_notify() go ahead on a > pmd_trans_splitting() pmd. We hold the page_table_lock so > __split_huge_page_map() must wait the pmdp_clear_flush_young_notify() to > complete before it can modify the pmd. The pmd is also still mapped in userland > so the young bit may materialize through a tlb miss before split_huge_page_map > runs. This will provide a more accurate page_referenced() behavior during > split_huge_page(). > > Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Reported-by: Michel Lespinasse <walken@xxxxxxxxxx> > Reviewed-by: Michel Lespinasse <walken@xxxxxxxxxx> Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>