From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1HI8Tl-00069n-4G for user-mode-linux-devel@lists.sourceforge.net; Fri, 16 Feb 2007 11:10:47 -0800 Received: from smtp004.mail.ukl.yahoo.com ([217.12.11.35]) by mail.sourceforge.net with smtp (Exim 4.44) id 1HI8Tg-0000On-TT for user-mode-linux-devel@lists.sourceforge.net; Fri, 16 Feb 2007 11:10:42 -0800 From: Blaisorblade Date: Fri, 16 Feb 2007 20:10:18 +0100 References: <20070215160001.GA6774@avocado.homenet> <200702152029.28670.blaisorblade@yahoo.it> <20070216170207.GC2427@metaxa.reflex> In-Reply-To: <20070216170207.GC2427@metaxa.reflex> MIME-Version: 1.0 Content-Disposition: inline Message-Id: <200702162010.18776.blaisorblade@yahoo.it> Subject: Re: [uml-devel] [UML] fix crash in block layer List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: Jason Lunz Cc: Jeff Dike , user-mode-linux-devel@lists.sourceforge.net, Jens Axboe On Friday 16 February 2007 18:02, Jason Lunz wrote: > On Thu, Feb 15, 2007 at 08:29:28PM +0100, Blaisorblade wrote: > > The following could be a suggestion, if max_low_pfn is not used between > > the old and the new moment of assignment (and it seems it is not). This > > is just an idea however: > blk_queue_bounce_limit() calls init_emergency_isa_pool() to get dma-zone > pages to use as bounce buffers when its caller passes a dma_addr limit > that is less than max_low_pfn. The BLK_BOUNCE_ANY macro is supposed to > mean "never bounce", and it's defined as: > #define BLK_BOUNCE_ANY ((u64)blk_max_pfn << PAGE_SHIFT) > So it presumes that max_pfn >= max_low_pfn. uml's mem_init() is > violating this assumption - when uml_reserved is subtracted from > max_pfn, we end up with max_pfn < max_low_pfn, so BLK_BOUNCE_ANY has the > opposite of the intended effect. blk_queue_bounce_limit therefore tries > to create a mempool with zone-dma pages on a no-dma-zone arch and the > kernel goes BUG(). Thanks for the explaination; but I meant that the meaning of those variables and the code to set them was convoluted. > So I think your idea is correct. It passes my testing - I can still use > lvm within uml. I have not tested CONFIG_HIGHMEM, but here's an > implementation against 2.6.20. Do not worry for HIGHMEM - I doubt it builds currently; uml_reserved is also used for other stuff. I've also verified that moving the assignment to max_low_pfn to later cannot possibly introduce bugs, as max_{low_,}pfn are not used by core kernel code. > Jeff, please drop my other patch and use this one. > Signed-off-by: Jason Lunz > > --- > arch/um/kernel/mem.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > Index: linux-2.6.20-uml/arch/um/kernel/mem.c > =================================================================== > --- linux-2.6.20-uml.orig/arch/um/kernel/mem.c > +++ linux-2.6.20-uml/arch/um/kernel/mem.c > @@ -63,8 +63,6 @@ > > void mem_init(void) > { > - max_low_pfn = (high_physmem - uml_physmem) >> PAGE_SHIFT; > - > /* clear the zero-page */ > memset((void *) empty_zero_page, 0, PAGE_SIZE); > > @@ -79,6 +77,7 @@ > > /* this will put all low memory onto the freelists */ > totalram_pages = free_all_bootmem(); > + max_low_pfn = totalram_pages; > #ifdef CONFIG_HIGHMEM > totalhigh_pages = highmem >> PAGE_SHIFT; > totalram_pages += totalhigh_pages; -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel