From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 6 Jun 2001 13:31:40 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH] reapswap for 2.4.5-ac10 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Marcelo Tosatti Cc: "Stephen C. Tweedie" , Alan Cox , =?iso-8859-1?Q?Andr=E9_Dahlqvist?= , linux-mm@kvack.org List-ID: On Tue, 5 Jun 2001, Marcelo Tosatti wrote: > On Tue, 5 Jun 2001, Stephen C. Tweedie wrote: > > On Tue, Jun 05, 2001 at 04:48:46PM -0300, Marcelo Tosatti wrote: > > > I'm resending the reapswap patch for inclusion into -ac series. > > > > Isn't it broken in this state? Checking page_count, page->buffers and > > PageSwapCache without the appropriate locks is dangerous. > > We hold the pagemap_lru_lock, so there will be no one doing lookups on > this swap page (get_swapcache_page() locks pagemap_lru_lock). > > Am I overlooking something here? mm/shmem.c:shmem_getpage_locked() and mm/swapfile.c:try_to_unuse() call delete_from_swap_cache_nolock(), both holding page lock, neither holding pagemap_lru_lock. Unless you hold the page lock, PageSwapCache(page) and page->index are volatile, but to find swap_count(page) you have to rely on both of them. TryLockPage()? Hugh -- 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/