On Wed, 21 Apr 2010, Mel Gorman wrote: > > > 2. Is the BUG_ON check in > > > include/linux/swapops.h#migration_entry_to_page() now wrong? (I > > > think yes, but I'm not sure and I'm having trouble verifying it) > > > > The bug check ensures that migration entries only occur when the page > > is locked. This patch changes that behavior. This is going too oops > > therefore in unmap_and_move() when you try to remove the migration_ptes > > from an unlocked page. > > > > It's not unmap_and_move() that the problem is occurring on but during a > page fault - presumably in do_swap_page but I'm not 100% certain. remove_migration_pte() calls migration_entry_to_page(). So it must do that only if the page is still locked. You need to ensure that the page is not unlocked in move_to_new_page() if the migration ptes are kept. move_to_new_page() only unlocks the new page not the original page. So that is safe. And it seems that the old page is also unlocked in unmap_and_move() only after the migration_ptes have been removed? So we are fine after all...? -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>