Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757785AbaFUFxR (ORCPT ); Sat, 21 Jun 2014 01:53:17 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47628 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752873AbaFUFxQ (ORCPT ); Sat, 21 Jun 2014 01:53:16 -0400 Date: Sat, 21 Jun 2014 06:53:07 +0100 From: Al Viro To: "Theodore Ts'o" , Dave Chinner , Jens Axboe , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: 32-bit bug in iovec iterator changes Message-ID: <20140621055306.GP18016@ZenIV.linux.org.uk> References: <20140619153550.GA12836@thunk.org> <53A308DE.7080000@fb.com> <20140619160801.GB4907@thunk.org> <20140619162144.GC4907@thunk.org> <20140619223820.GN4453@dastard> <20140621035144.GA8526@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140621035144.GA8526@thunk.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 20, 2014 at 11:51:44PM -0400, Theodore Ts'o wrote: > On Fri, Jun 20, 2014 at 08:38:20AM +1000, Dave Chinner wrote: > > > > Short reads are more likely a bug in all the iovec iterator stuff > > that got merged in from the vfs tree. ISTR a 32 bit-only bug in that > > stuff go past in to do with not being able to partition a 32GB block > > dev on a 32 bit system due to a 32 bit size_t overflow somewhere.... > > Dave Chinner called it. > > Al, I'm seeing a regression which shows up using a 32-bit x86 kernel. > The symptoms of the bug is when run under KVM, with a 5 GB /dev/vdc > virtual block device, a read at offset 2 ** 30 fails with a short > read: > > # dd if=/dev/vdc of=/dev/null bs=4k skip=262144 count=1 > 0+0 records in > 0+0 records out > 0 bytes (0 B) copied, 0.0164144 s, 0.0 kB/s Argh... ed include/linux/uio.h <