From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Ball Subject: Re: [PATCH] mmc: mmci: reduce max_blk_count to avoid overflowing max_req_size Date: Fri, 02 Mar 2012 16:02:38 -0500 Message-ID: References: <1330082721-6021-1-git-send-email-will.deacon@arm.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from void.printf.net ([89.145.121.20]:60455 "EHLO void.printf.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753621Ab2CBVCq (ORCPT ); Fri, 2 Mar 2012 16:02:46 -0500 In-Reply-To: <1330082721-6021-1-git-send-email-will.deacon@arm.com> (Will Deacon's message of "Fri, 24 Feb 2012 11:25:21 +0000") Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Will Deacon Cc: linux-mmc@vger.kernel.org, Pierre Ossman Hi Will, On Fri, Feb 24 2012, Will Deacon wrote: > On a system with large pages (64k in my case), the following BUG is > triggered in MMC core: > > [ 2.338023] BUG: failure at drivers/mmc/core/core.c:221/mmc_start_request()! > [ 2.338102] Kernel panic - not syncing: BUG! > [ 2.338155] Call trace: > [ 2.338228] [] dump_backtrace+0x0/0x120 > [ 2.338317] [] dump_stack+0x14/0x1c > [ 2.338403] [] panic+0xbc/0x1f0 > [ 2.338498] [] mmc_start_request+0x154/0x184 > [ 2.338600] [] mmc_start_req+0x110/0x140 > [ 2.338701] [] mmc_blk_issue_rw_rq+0x7c/0x39c > [ 2.338804] [] mmc_blk_issue_rq+0x1c0/0x468 > [ 2.338905] [] mmc_queue_thread+0x68/0x118 > [ 2.338995] [] kthread+0x84/0x8c > > This is because of a 64k request with a max_req_size of 64k-1 bytes. > > The following patch fixes the problem by limiting the max_blk_count > such that max_blk_count * max_blk_size == max_req_size. I couldn't > pursuade the compiler to emit a shift instead of a div without encoding > the shift explicitly. > > Cc: Pierre Ossman > Cc: Chris Ball > Signed-off-by: Will Deacon Thanks, pushed to mmc-next for 3.3. - Chris. -- Chris Ball One Laptop Per Child