From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44437) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XW8x5-0000Fi-EW for qemu-devel@nongnu.org; Mon, 22 Sep 2014 15:07:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XW8wz-0002TD-AR for qemu-devel@nongnu.org; Mon, 22 Sep 2014 15:07:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64823) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XW8wz-0002Rq-2d for qemu-devel@nongnu.org; Mon, 22 Sep 2014 15:07:05 -0400 Message-ID: <54207349.2000107@redhat.com> Date: Mon, 22 Sep 2014 21:06:49 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1409935888-18552-1-git-send-email-pl@kamp.de> <1409935888-18552-5-git-send-email-pl@kamp.de> <541AE887.9050607@redhat.com> <541C3095.4040405@redhat.com> <541FEF3A.30909@kamp.de> In-Reply-To: <541FEF3A.30909@kamp.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/4] block: avoid creating oversized writes in multiwrite_merge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, qemu-devel@nongnu.org, stefanha@redhat.com, mreitz@redhat.com Il 22/09/2014 11:43, Peter Lieven ha scritto: > This series aims not at touching default behaviour. The default for max_transfer_length > is 0 (no limit). max_transfer_length is a limit that MUST be satisfied otherwise the request > will fail. And Patch 2 aims at catching this fail earlier in the stack. Understood. But the right fix is to avoid that backend limits transpire into guest ABI, not to catch the limits earlier. So the right fix would be to implement request splitting. Since we never had a bug report about this, I'm not pushing to implement splitting. However, patch 2 is still wrong. Patch 4 instead is fixing a real bug, so it's very much welcome. Paolo > Currently, we only > have a limit for iSCSI. Without Patch 2 it would fail after we have send > the command to > the target. And without Patch 4 it may happen that multiwrite_merge > traps the into the limit. > > Maybe I should adjust the description of max_transfer_length?