From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NXYtp-0008Kz-4D for qemu-devel@nongnu.org; Wed, 20 Jan 2010 06:39:01 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NXYtk-0008J1-As for qemu-devel@nongnu.org; Wed, 20 Jan 2010 06:39:00 -0500 Received: from [199.232.76.173] (port=32895 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NXYtk-0008Ir-36 for qemu-devel@nongnu.org; Wed, 20 Jan 2010 06:38:56 -0500 Received: from mx1.redhat.com ([209.132.183.28]:7366) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NXYtj-00059o-Lf for qemu-devel@nongnu.org; Wed, 20 Jan 2010 06:38:55 -0500 Message-ID: <4B56EB0F.2020409@redhat.com> Date: Wed, 20 Jan 2010 12:37:51 +0100 From: Kevin Wolf MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] block: prevent multiwrite_merge from creating too large iovecs References: <20100119211539.GA4383@lst.de> In-Reply-To: <20100119211539.GA4383@lst.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christoph Hellwig Cc: qemu-devel@nongnu.org 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 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? What about handling it transparently in qemu_pwritev/preadv and laio_submit? Logically, it's a limitation of the backend anyway and not a generic restriction. To underline that it's a backend/platform dependent thing: Your patch breaks the mingw build for me. Kevin