linux-kernel - Re: 32-bit bug in iovec iterator changes

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Date:	Sat, 21 Jun 2014 06:53:07 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Theodore Ts'o <tytso@....edu>, Dave Chinner <david@...morbit.com>,
	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: Re: 32-bit bug in iovec iterator changes

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 <<EOF
/iov_iter_truncate/s/size_t/u64/
w
q
EOF

Could you check if that fixes the sucker?
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