From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 77A266B00F5 for ; Wed, 3 Jun 2009 13:51:25 -0400 (EDT) Date: Tue, 2 Jun 2009 15:24:41 +0200 From: Nick Piggin Subject: Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3 Message-ID: <20090602132441.GC6262@wotan.suse.de> References: <20090528082616.GG6920@wotan.suse.de> <20090528095934.GA10678@localhost> <20090528122357.GM6920@wotan.suse.de> <20090528135428.GB16528@localhost> <20090601115046.GE5018@wotan.suse.de> <20090601183225.GS1065@one.firstfloor.org> <20090602120042.GB1392@wotan.suse.de> <20090602124757.GG1065@one.firstfloor.org> <20090602125713.GG1392@wotan.suse.de> <20090602132538.GK1065@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090602132538.GK1065@one.firstfloor.org> Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: Wu Fengguang , "hugh@veritas.com" , "riel@redhat.com" , "akpm@linux-foundation.org" , "chris.mason@oracle.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" List-ID: On Tue, Jun 02, 2009 at 03:25:38PM +0200, Andi Kleen wrote: > On Tue, Jun 02, 2009 at 02:57:13PM +0200, Nick Piggin wrote: > > > > not a big deal and just avoids duplicating code. I attached an > > > > (untested) patch. > > > > > > Thanks. But the function in the patch is not doing the same what > > > the me_pagecache_clean/dirty are doing. For once there is no error > > > checking, as in the second try_to_release_page() > > > > > > Then it doesn't do all the IO error and missing mapping handling. > > > > Obviously I don't mean just use that single call for the entire > > handler. You can set the EIO bit or whatever you like. The > > "error handling" you have there also seems strange. You could > > retain it, but the page is assured to be removed from pagecache. > > The reason this code double checks is that someone could have > a reference (remember we can come in any time) we cannot kill immediately. Can't kill what? The page is gone from pagecache. It may remain other kernel references, but I don't see why this code will consider this as a failure (and not, for example, a raised error count). > > > The page_mapped() check is useless because the pages are not > > > mapped here etc. > > > > That's OK, it is a core part of the protocol to prevent > > truncated pages from being mapped, so I like it to be in > > that function. > > > > (you are also doing extraneous page_mapped tests in your handler, > > so surely your concern isn't from the perspective of this > > error handler code) > > We do page_mapping() checks, not page_mapped checks. > > I know details, but ... +static int me_pagecache_clean(struct page *p) +{ + if (!isolate_lru_page(p)) + page_cache_release(p); + + if (page_has_private(p)) + do_invalidatepage(p, 0); + if (page_has_private(p) && !try_to_release_page(p, GFP_NOIO)) + Dprintk(KERN_ERR "MCE %#lx: failed to release buffers\n", + page_to_pfn(p)); + + /* + * remove_from_page_cache assumes (mapping && !mapped) + */ + if (page_mapping(p) && !page_mapped(p)) { ^^^^^^^^^^^^^^^ + remove_from_page_cache(p); + page_cache_release(p); + } + + return RECOVERED; > > > we would also need to duplicate most of the checking outside > > > the function anyways and there wouldn't be any possibility > > > to share the clean/dirty variants. If you insist I can > > > do it, but I think it would be significantly worse code > > > than before and I'm reluctant to do that. > > > > I can write you the patch for that too if you like. > > Ok I will write it, but I will add a comment saying that Nick forced > me to make the code worse @) > > It'll be fairly redundant at least. If it's that bad, then I'll be happy to rewrite it for you. > > > > if you already have other large ones. > > > > > > That's unclear too. > > > > You can't do much about most kernel pages, and dirty metadata pages > > are both going to cause big problems. User pagetable pages. Lots of > > stuff. > > User page tables was on the todo list, these are actually relatively > easy. The biggest issue is to detect them. > > Metadata would likely need file system callbacks, which I would like to > avoid at this point. So I just don't know why you argue the point that you have lots of large holes left. -- 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