From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030761Ab2GLTjv (ORCPT ); Thu, 12 Jul 2012 15:39:51 -0400 Received: from mail.digidescorp.com ([50.73.98.161]:22889 "EHLO mail.digidescorp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030747Ab2GLTju (ORCPT ); Thu, 12 Jul 2012 15:39:50 -0400 DomainKey-Signature: a=rsa-sha1; s=MDaemon; d=digidescorp.com; c=simple; q=dns; h=message-id:from; b=sAPndErFKXR2iCEzombnEhs6KobJXuqaR8MC9YYgmky7aYunA3sFr/lfkbfe JSn72aBEKU/JY3f5GG8fwoDYVwYRYZPiFSbUvuJujZOXYvYEar83vgK8y Zas45Li5N5eUp1GXFi7nnQNv3ZkVv3tmhR9mV8QtuYqeR6w508ceHs=; X-Spam-Processed: mail.digidescorp.com, Thu, 12 Jul 2012 14:39:48 -0500 (not processed: message from trusted or authenticated source) X-Authenticated-Sender: steve@digidescorp.com X-Return-Path: prvs=15403394f6=steve@digidescorp.com X-Envelope-From: steve@digidescorp.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org Message-ID: <1342121986.2156.20.camel@iscandar.digidescorp.com> Subject: Re: mount -o loop with truncated dosdisk.img uses 100% cpu and can't be killed From: "Steven J. Magnani" To: OGAWA Hirofumi Cc: Stevie Trujillo , linux-kernel@vger.kernel.org, Jens Axboe Date: Thu, 12 Jul 2012 14:39:46 -0500 In-Reply-To: <87k3y8yed3.fsf@devron.myhome.or.jp> References: <20120712162828.3f561315@localhost> <1342106206.2156.2.camel@iscandar.digidescorp.com> <87k3y8yed3.fsf@devron.myhome.or.jp> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.3 (3.4.3-1.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-07-13 at 04:21 +0900, OGAWA Hirofumi wrote: > > On Thu, 2012-07-12 at 16:28 +0200, Stevie Trujillo wrote: > >> Hello, > >> > >> I was trying to create a bootdisk to update my BIOS, and accidentially > >> made a 512byte image with only the FreeDOS header in it. > >> > >> ( Linux 3.4.4 ) > >> # mount -o loop dosdisk.img /tmp > >> ^C^C^C > >> It uses 100% CPU and doesn't listen to me when I do ^C, kill -9 etc. I > >> think this means it's stuck in the kernel? > It looks like the bug of __getblk_slow(). If requested block was beyond > end of device, __find_get_block() will find buffer_mapped()'s buffer, > but block >= end_block is unmapped. So, it can be loop. > > The following patch fixes it? If it fix, there are some options to check > it. > > a) Check it like this patch and warn. > b) (a), but without warn. > c) Check it in init_page_buffers() and return -EIO or such > > Well, anyway, Cc to Jens. > > Signed-off-by: OGAWA Hirofumi > --- > > fs/buffer.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff -puN fs/buffer.c~debug fs/buffer.c > --- tux3fs/fs/buffer.c~debug 2012-07-13 04:10:40.000000000 +0900 > +++ tux3fs-hirofumi/fs/buffer.c 2012-07-13 04:11:50.000000000 +0900 > @@ -1055,6 +1055,13 @@ __getblk_slow(struct block_device *bdev, > dump_stack(); > return NULL; > } > + if (block >= blkdev_max_block(I_BDEV(bdev->bd_inode))) { > + printk(KERN_ERR "getblk(): block %llu, end_block %llu\n", > + (unsigned long long)block, > + (unsigned long long)blkdev_max_block(I_BDEV(bdev->bd_inode))); > + dump_stack(); > + return NULL; > + } > > for (;;) { > struct buffer_head * bh; > _ This fixes the hang, but I'm not sure dump_stack() is a good idea. I get almost 100 lines of stack dumps and error messages in my kernel log. Also, I was a little surprised to see that mount completes successfully. ------------------------------------------------------------------------ Steven J. Magnani "I claim this network for MARS! www.digidescorp.com Earthling, return my space modulator!" #include