From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32817) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAf66-0001yX-5o for qemu-devel@nongnu.org; Thu, 02 Jul 2015 10:04:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZAf61-0006em-3H for qemu-devel@nongnu.org; Thu, 02 Jul 2015 10:04:14 -0400 References: <55952D97.7040009@redhat.com> <559540F6.9090800@redhat.com> <55954384.9010906@redhat.com> From: Paolo Bonzini Message-ID: <559544C4.4050809@redhat.com> Date: Thu, 2 Jul 2015 16:03:48 +0200 MIME-Version: 1.0 In-Reply-To: <55954384.9010906@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laurent Vivier , Stefan Hajnoczi , Programmingkid Cc: Kevin Wolf , Peter Maydell , John Snow , qemu-devel qemu-devel , Qemu-block On 02/07/2015 15:58, Laurent Vivier wrote: > Since any /dev entry can be treated as a raw disk image, it is worth > noting which devices can be accessed when and how. /dev/rdisk nodes are > character-special devices, but are "raw" in the BSD sense and force > block-aligned I/O. They are closer to the physical disk than the buffer > cache. /dev/disk nodes, on the other hand, are buffered block-special > devices and are used primarily by the kernel's filesystem code. So the right thing to do would not be just to set need_alignment, but to probe it like we do on Linux for BDRV_O_NO_CACHE. I'm okay with doing the simple thing, but it needs a comment for non-BSDers. Paolo