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Re: [Qemu-devel] [PATCH 1/2] qemu-io: don't allow I/O operations larger

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH 1/2] qemu-io: don't allow I/O operations larger than INT_MAX
Date: Tue, 31 Jan 2017 10:31:32 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0

On 01/31/2017 10:09 AM, Alberto Garcia wrote:
> Passing a request size larger than INT_MAX to any of the I/O commands
> results in an error. While 'read' and 'write' handle the error
> correctly, 'aio_read' and 'aio_write' hit an assertion:
> blk_aio_read_entry: Assertion `rwco->qiov->size == acb->bytes' failed.
> The reason is that the QEMU I/O code cannot handle request sizes
> larger than INT_MAX, so this patch makes qemu-io check that all values
> are within range.

Ideally, it would be nice to fix the block layer to allow larger
requests (since we already have code to auto-fragment down to device
limits, we should be able to rely on that code instead of having to
duplicate artificial constraints everywhere else in the tree).  But
that's a bigger task, and this is a good patch in the interim.

> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  qemu-io-cmds.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)

Reviewed-by: Eric Blake <address@hidden>

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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