On Mon, Feb 7, 2011 at 4:47 PM, Michel Lespinasse <walken@xxxxxxxxxx> wrote: > > vmscan can lazily find pages that are mapped within VM_LOCKED vmas, > and set the PageMlocked bit on these pages, transfering them onto the > unevictable list. When do_wp_page() breaks COW within a VM_LOCKED vma, > it may need to clear PageMlocked on the old page and set it on the > new page instead. > > This change fixes an issue where do_wp_page() was clearing PageMlocked on > the old page while the pte was still pointing to it (as well as rmap). > Therefore, we were not protected against vmscan immediately trasnfering > the old page back onto the unevictable list. This could cause pages to > get stranded there forever. > > I propose to move the corresponding code to the end of do_wp_page(), > after the pte (and rmap) have been pointed to the new page. Additionally, > we can use munlock_vma_page() instead of clear_page_mlock(), so that > the old page stays mlocked if there are still other VM_LOCKED vmas > mapping it. > > Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> (but I have to say, do_wp_page() grows even ughlier!) -- 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>