From owner-freebsd-current@FreeBSD.ORG Mon Feb 8 16:29:46 2010 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 682BD106566C; Mon, 8 Feb 2010 16:29:46 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-iw0-f198.google.com (mail-iw0-f198.google.com [209.85.223.198]) by mx1.freebsd.org (Postfix) with ESMTP id 196698FC13; Mon, 8 Feb 2010 16:29:45 +0000 (UTC) Received: by iwn36 with SMTP id 36so986095iwn.3 for ; Mon, 08 Feb 2010 08:29:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to:cc :content-type:content-transfer-encoding; bh=v090fvmEcjnOuEfb9+Q1ptMYhCBwrT6zpaAcYgZctAM=; b=SdybM4JkaCAzdVzCyprHs5Mz7wNIGrd8RlJFx8AzmK2YvUcRcK39Qj8vxJPKV3IyMq zR8suuGnnnuSBBLKYDNACetnw2GL15KXoUKh/2PO7JbWMhExk2g2qzcbLfcmnjvfSvr0 guzCI/Wafn/LYWVug/yNZ4j8Z4s6XKtOlQ+Qk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=G/Tb7g1gOFUjPJkYsgJah/XeoiRtac+SEy1xAZyUITda7LDXFGNnDDAl1Zt3UYJWZC 9WeVNKCCIY01g2VeTxePP6Pd4yW5Voa+wr6m0Vo2lEtLd93+dw4zzb/EoD533+aKSe+L 8sjYs9Yohg5j51mf03af2DRCdVlDXnq7dKujM= MIME-Version: 1.0 Sender: asmrookie@gmail.com Received: by 10.231.145.5 with SMTP id b5mr6143834ibv.70.1265646584922; Mon, 08 Feb 2010 08:29:44 -0800 (PST) In-Reply-To: <20100208154158.GM9991@deviant.kiev.zoral.com.ua> References: <20100207160031.GA27434@muon.cran.org.uk> <201002080900.44745.jhb@freebsd.org> <20100208145354.GJ9991@deviant.kiev.zoral.com.ua> <3bbf2fe11002080701u35a3e419ke562735f4f00ce97@mail.gmail.com> <3bbf2fe11002080706k11275a9evbf8a7fa1b14b447f@mail.gmail.com> <20100208150818.GL9991@deviant.kiev.zoral.com.ua> <3bbf2fe11002080740q1da560c8r8c8d92a1053d021b@mail.gmail.com> <20100208154158.GM9991@deviant.kiev.zoral.com.ua> Date: Mon, 8 Feb 2010 17:29:44 +0100 X-Google-Sender-Auth: 1557550056b70b5d Message-ID: <3bbf2fe11002080829l4d5bb55ue82e3ce5f65f2ae2@mail.gmail.com> From: Attilio Rao To: Kostik Belousov Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: bzeeb+freebsd+lor@zabbadoz.net, Bruce Cran , freebsd-current@freebsd.org Subject: Re: LOR: vfs_mount.c (ufs) / msdosfs_vfsops.c (devfs) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Feb 2010 16:29:46 -0000 2010/2/8 Kostik Belousov : > On Mon, Feb 08, 2010 at 04:40:29PM +0100, Attilio Rao wrote: >> 2010/2/8 Kostik Belousov : >> > On Mon, Feb 08, 2010 at 04:06:56PM +0100, Attilio Rao wrote: >> >> 2010/2/8 Attilio Rao : >> >> > 2010/2/8 Kostik Belousov : >> >> >> On Mon, Feb 08, 2010 at 09:00:44AM -0500, John Baldwin wrote: >> >> >>> On Sunday 07 February 2010 11:00:32 am Bruce Cran wrote: >> >> >>> > Running -CURRENT from today, I unmounted the msdosfs filesystem= on my >> >> >>> > phone and got the following LOR: >> >> >>> > >> >> >>> > lock order reversal: >> >> >>> > =C2=A01st 0xffffff00c51279f8 ufs (ufs) @ /usr/src/sys/kern/vfs_= mount.c:1204 >> >> >>> > =C2=A02nd 0xffffff010b892278 devfs (devfs) @ >> >> >>> > /usr/src/sys/modules/msdosfs/../../fs/msdosfs/msdosfs_vfsops.c:= 944 >> >> >>> > KDB: stack backtrace: >> >> >>> > db_trace_self_wrapper() at db_trace_self_wrapper+0x2a >> >> >>> > _witness_debugger() at witness_debugger+0x2e >> >> >>> > witness_checkorder() at witness_checkorder+0x81e >> >> >>> > __lockmgr_args() at __lockmgr_args+0xd11 >> >> >>> > vop_stdlock() at vop_stdlock+0x39 >> >> >>> > VOP_LOCK1_APV() VOP_LOCK1_APV+0x9b >> >> >>> > _vn_lock() at _vn_lock+0x47 >> >> >>> > msdosfs_sync() at msdosfs_sync+0x227 >> >> >>> > dounmount() at dounmount+0x2ca >> >> >>> > unmount() at unmount+0x216 >> >> >>> > syscall() at syscall+0x2a2 >> >> >>> > Xfast_syscall() at Xfast_syscall+0xe1 >> >> >>> > --- syscall (22, FreeBSD ELF64, unmount), rip =3D 0x8006a1e3c, = rsp =3D >> >> >>> > 0x7fffffffe3a8, rbp =3D 0x800c08010 --- >> >> >>> >> >> >>> This is due to holding a lock on the coveredvp vnode for most of = unmount(2). >> >> >>> Probably it should not be held for all of that. =C2=A0Perhaps it = is safe to just >> >> >>> keep the vnode referenced instead, or could the handling for cove= redvp just >> >> >>> move to the end of the function where it is now vput? >> >> >> >> >> >> Among other things, holding vnode lock on covered vnode prevents p= arallel >> >> >> unmounts of the same mount point. >> >> > >> >> > Uhm, I think that this should be hanlded by MNTK_UNMOUNT already (a= nd >> >> > thus stopping forced unmounts too). >> >> >> >> In other words probabilly keeping coveredvnode held until MNTK_UNMOUN= T >> >> and then refcounting it should be fine. >> > >> > Actually, the coveredvp then might be reclaimed ? Failed unmount then >> > cannot recover. >> >> I thought on domount() we did holdcount the coveredvp for the time being= ? >> If we don't, maybe we should. > Hold or ref does not prevent reclaim. Oh right, I readed recycle. Attilio --=20 Peace can only be achieved by understanding - A. Einstein