On 08/22/2012 12:12 PM, Hugh Dickins wrote: > On Wed, 22 Aug 2012, Xiao Guangrong wrote: >> On 08/21/2012 11:06 PM, Andrea Arcangeli wrote: >>> >>> The KSM usage of it looks safe because it will only establish readonly >>> ptes with it. >> >> Hmm, in KSM code, i found this code in replace_page: >> >> set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); >> >> It is possible to establish a writable pte, no? > > No: we only do KSM in private vmas (!VM_SHARED), and because of the > need to CopyOnWrite in those, vm_page_prot excludes write permission: > write permission has to be added on COW fault. After read the code carefully, yes, you are right. Thank you very much for your explanation, Hugh! :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>