On Sun, May 26, 2013 at 07:44:56AM -0400, KOSAKI Motohiro wrote: > > + /* > > + * By flagging sys_swapon, a sysadmin can tell us to > > + * either do sinle-time area discards only, or to just > > + * perform discards for released swap page-clusters. > > + * Now it's time to adjust the p->flags accordingly. > > + */ > > + if (swap_flags & SWAP_FLAG_DISCARD_ONCE) > > + p->flags &= ~SWP_PAGE_DISCARD; > > + else if (swap_flags & SWAP_FLAG_DISCARD_PAGES) > > + p->flags &= ~SWP_AREA_DISCARD; > > When using old swapon(8), this code turn off both flags, right? As the flag that enables swap discards SWAP_FLAG_DISCARD remains meaning the same it meant before, when using old swapon(8) (SWP_PAGE_DISCARD|SWP_AREA_DISCARD) will remain flagged when discard is enabled, so we keep doing discards the same way we did before (at swapon, and for every released page-cluster). The flags are removed orthogonally only when the new swapon(8) selects one of the particular discard policy available by using either SWAP_FLAG_DISCARD_ONCE, or SWAP_FLAG_DISCARD_PAGES flags. -- 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>