From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 22 Apr 2008 18:57:34 +0900 From: KAMEZAWA Hiroyuki Subject: Re: Warning on memory offline (and possible in usual migration?) Message-Id: <20080422185734.936cd80d.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20080422094352.GB23770@wotan.suse.de> References: <20080414145806.c921c927.kamezawa.hiroyu@jp.fujitsu.com> <20080422045205.GH21993@wotan.suse.de> <20080422165608.7ab7026b.kamezawa.hiroyu@jp.fujitsu.com> <20080422094352.GB23770@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Christoph Lameter , "linux-mm@kvack.org" , Andrew Morton , GOTO List-ID: On Tue, 22 Apr 2008 11:43:52 +0200 Nick Piggin wrote: > > > > > > > > > > if (PageDirty(page)) { > > > > > clear_page_dirty_for_io(page); > > > > > set_page_dirty(newpage);------------------------(**) > > > > > } > > > > > > > > > > == > > > > > Then, Uptodate() is copied before set_page_dirty(). > > > > > So, "page" is not Uptodate and Dirty when it reaches (**) > > > > > > > > The page will be marked uptodate before we reach ** so its okay in > > > > general. If a page is not uptodate then we should not be getting here. > > > > > > > > An !uptodate page is not migratable. Maybe we need to add better checking? > > > > > > Why is an !uptodate page not migrateable, and where are you testing to > > > prevent that? > > > > > > > I'm sorry if I don't understand correctly, in usual, can I consider > > !PageUptodate() page is under I/O or some unstable state ? > > No, it need not be under IO or in some unstable state. Christoph just > said that migration can't handle !uptodate pages, and I'm very > curious as to why not, and what is in place to prevent that from > happening. > I myself have no idea about "why". I thought that page_lock() can keep us from migrating a page under I/O before I found this WARNING. Thanks -Kame -- 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