From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC][PATCH] putback_lru_page()/unevictable page handling rework v3 From: Lee Schermerhorn In-Reply-To: <20080624184122.D838.KOSAKI.MOTOHIRO@jp.fujitsu.com> References: <20080621185408.E832.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080624184122.D838.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain Date: Tue, 24 Jun 2008 13:15:41 -0400 Message-Id: <1214327741.6563.17.camel@lts-notebook> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki , linux-mm , LKML , Rik van Riel List-ID: On Tue, 2008-06-24 at 18:49 +0900, KOSAKI Motohiro wrote: > I found one bug ;) > > > -int putback_lru_page(struct page *page) > > +#ifdef CONFIG_UNEVICTABLE_LRU > > +void putback_lru_page(struct page *page) > > { > > int lru; > > - int ret = 1; > > int was_unevictable; > > > > - VM_BUG_ON(!PageLocked(page)); > > VM_BUG_ON(PageLRU(page)); > > > > + was_unevictable = TestClearPageUnevictable(page); > > + > > +redo: > > lru = !!TestClearPageActive(page); > > - was_unevictable = TestClearPageUnevictable(page); /* for page_evictable() */ > > (snip) > > > + mem_cgroup_move_lists(page, lru); > > + > > + /* > > + * page's status can change while we move it among lru. If an evictable > > + * page is on unevictable list, it never be freed. To avoid that, > > + * check after we added it to the list, again. > > + */ > > + if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { > > + if (!isolate_lru_page(page)) { > > + put_page(page); > > + goto redo; > > at this point, We should call ClearPageUnevictable(). > otherwise, BUG() is called on isolate_lru_pages(). > To which BUG() are you referring here? There used to be a BUG_ON(PageUnevictable(page)) in page_evictable(), but Kame-san removed that. By the wah, we'll never take the retry because 'lru' never == LRU_UNEVICTABLE in this version of putback_lru_page(). Patch to follow. Lee -- 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