From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 14 Apr 2006 11:48:09 -0700 (PDT) From: Christoph Lameter Subject: Re: Implement lookup_swap_cache for migration entries In-Reply-To: <20060414113104.72a5059b.akpm@osdl.org> Message-ID: References: <20060413235406.15398.42233.sendpatchset@schroedinger.engr.sgi.com> <20060413235416.15398.49978.sendpatchset@schroedinger.engr.sgi.com> <20060413171331.1752e21f.akpm@osdl.org> <20060413174232.57d02343.akpm@osdl.org> <20060413180159.0c01beb7.akpm@osdl.org> <20060413222921.2834d897.akpm@osdl.org> <20060414113104.72a5059b.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: hugh@veritas.com, linux-kernel@vger.kernel.org, lee.schermerhorn@hp.com, linux-mm@kvack.org, taka@valinux.co.jp, marcelo.tosatti@cyclades.com, kamezawa.hiroyu@jp.fujitsu.com List-ID: On Fri, 14 Apr 2006, Andrew Morton wrote: > > @@ -305,6 +306,12 @@ struct page * lookup_swap_cache(swp_entr > > { > > struct page *page; > > > > + if (is_migration_entry(entry)) { > > + page = migration_entry_to_page(entry); > > + get_page(page); > > + return page; > > + } > > What locking ensures that the state of `entry' remains unaltered across the > is_migration_entry() and migration_entry_to_page() calls? entry is a variable passed by value to the function. > > +/* > > + * Must use a macro for lookup_swap_cache since the functions > > + * used are only available in certain contexts. > > + */ > > +#define lookup_swap_cache(__swp) \ > > +({ struct page *p = NULL; \ > > + if (is_migration_entry(__swp)) { \ > > + p = migration_entry_to_page(__swp); \ > > + get_page(p); \ > > + } \ > > + p; \ > > +}) > > hm. Can nommu do any of this? If page migration is off (methinks nommu may not support numa) then the fallback functions are used. Fallback is is_migration_entry() == 0 therefore #define lookup_swap_cache(__swp) NULL like before. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org