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Date: Wed, 20 Jan 2010 17:24:34 +0100
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] [PATCH] block: prevent multiwrite_merge from
	creating too large iovecs
Message-ID: <20100120162434.GA7212@lst.de>
References: <20100119211539.GA4383@lst.de> <4B56EB0F.2020409@redhat.com>
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, qemu-devel@nongnu.org

On Wed, Jan 20, 2010 at 12:37:51PM +0100, Kevin Wolf wrote:
> Am 19.01.2010 22:15, schrieb Christoph Hellwig:
> > If we go over the maximum number of iovecs support by syscall we get
> > back EINVAL from the kernel which translate to I/O errors for the guest.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Is this really enough? We don't check for IOV_MAX in any other place, so
> can't we get a too big request directly from virtio-blk?

Currently the virtqueue is limited to 1024 iovecs, but I plan to put in
some better infrastructure to deal with the queue limit.  For now this
patch fixes an issue that we see with real life setups.