Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:49625 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751707AbbGBIZd (ORCPT ); Thu, 2 Jul 2015 04:25:33 -0400 Date: Thu, 2 Jul 2015 09:25:30 +0100 From: Al Viro To: Andrey Ryabinin Cc: Linus Torvalds , LKML , linux-fsdevel , "Aneesh Kumar K.V" , Eric Van Hensbergen , linux-nfs@vger.kernel.org Subject: Re: running out of tags in 9P (was Re: [git pull] vfs part 2) Message-ID: <20150702082529.GJ17109@ZenIV.linux.org.uk> References: <20150701082753.GD17109@ZenIV.linux.org.uk> <5593A7A0.6050400@samsung.com> <20150701085507.GE17109@ZenIV.linux.org.uk> <5593CE37.4070307@samsung.com> <20150701184408.GF17109@ZenIV.linux.org.uk> <20150702032042.GA32613@ZenIV.linux.org.uk> <20150702041046.GG17109@ZenIV.linux.org.uk> <20150702075932.GI17109@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, Jul 02, 2015 at 11:19:03AM +0300, Andrey Ryabinin wrote: > Besides qemu, I've also tried kvmtool with the same result. IOW I'm seeing > this under kvmtool as well. It just takes a bit longer to reproduce > this in kvmtool. > > > The bug I suspected to be the cause of that is in tag allocation in > > net/9p/client.c - we could end up wrapping around 2^16 with enough pending > > requests and that would have triggered that kind of mess. However, Andrey > > doesn't see that test (tag wraparound in p9_client_prepare_req()) trigger. > > BTW, was that on the run where debugging printk in p9_client_write() *did* > > trigger? > > Yes, WARN_ON_ONCE() in p9_client_prepare_req() didn't trigger, > but debug printk in p9_client_write() *did* trigger. Bloody wonderful... Could you check if v9fs_write() in qemu hw/9pfs/virtio-9p.c ever gets to offset = 7; err = pdu_marshal(pdu, offset, "d", total); with total > count on your testcase?