> Hi, > > I have been wondering about the following: > > Before the THP work, the if (vma->vm_flags & VM_LOCKED) test in > page_referenced_one() was placed after the page_check_address() call, > but now it is placed above it. Could this be a problem ? > > My understanding is that the page_check_address() check may return > false positives - for example, if an anon page was created before a > process forked, rmap will indicate that the page could be mapped in > both of the processes, even though one of them might have since broken > COW. What would happen if the child process mlocks the corresponding > VMA ? my understanding is that this would break COW, but not cause > rmap to be updated, so the parent's page would still be marked in rmap > as being possibly mapped in the children's VM_LOCKED vma. With the > VM_LOCKED check now placed above the page_check_address() call, this > would cause vmscan to see both the parent's and the child's pages as > being unevictable. > > Am I missing something there ? In particular, I am not sure if marking > the children's VMA as mlocked would somehow cause rmap to realize it > can't share pages with the parent anymore (but I don't think that's > the case, and it could cause other issues if it was...) Hi I think you are right. page_check_address() should be called before VM_LOCKED check. -- 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>