From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 16 Jan 2006 12:32:14 +0000 (GMT) From: Hugh Dickins Subject: Re: Race in new page migration code? In-Reply-To: Message-ID: References: <20060114155517.GA30543@wotan.suse.de> <20060114181949.GA27382@wotan.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Nick Piggin , Andrew Morton , Linux Kernel Mailing List , Linux Memory Management List List-ID: On Sun, 15 Jan 2006, Christoph Lameter wrote: > On Sun, 15 Jan 2006, Hugh Dickins wrote: > > > > Good. And whether it's your or Nick's patch that goes in, please also > > remove that PageReserved test which you recently put in check_pte_range. > > Zero pages are still marked reserved AFAIK. Why not check for it? Indeed they are, at present and quite likely into posterity. But they're not a common case here, and migrate_page_add now handles them silently, so why bother to complicate it with an unnecessary check? You added the test because the WARN_ON fired, you're now doing the right thing and removing the WARN_ON because it was inevitably racy, so it would make sense to remove the PageReserved test too. If you look through the rest of mm/, you'll find 2.6.15 removed all the PageReserved tests, except at the low level in page_alloc.c: so it's retrograde for you to be adding one back here. Testing PageLRU would be more relevant, if you insist on such a test. Or have you found the zero page mapcount distorting get_stats stats? If that's an issue, then better add a commented test for it there. Hmm, that battery of unusual tests at the start of migrate_page_add is odd: the tests don't quite match the comment, and it isn't clear what reasoning lies behind the comment anyway. 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/ . Don't email: email@kvack.org