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Wed, 27 Nov 2019 19:08:09 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id D75392202E9; Wed, 27 Nov 2019 14:08:08 -0500 (EST) Date: Wed, 27 Nov 2019 14:08:08 -0500 From: Vivek Goyal To: "Dr. David Alan Gilbert" Subject: Re: [Virtio-fs] [PATCH 4/4] virtiofsd: Implement blocking posix locks Message-ID: <20191127190808.GA18507@redhat.com> References: <20191115205543.1816-1-vgoyal@redhat.com> <20191115205543.1816-5-vgoyal@redhat.com> <20191122174732.GL2785@work-vm> <20191125154414.GC13247@redhat.com> <20191126130229.GG2928@work-vm> MIME-Version: 1.0 In-Reply-To: <20191126130229.GG2928@work-vm> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: JTPhCQzYPbq9m2Qp5U7vYA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, miklos@szeredi.hu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Nov 26, 2019 at 01:02:29PM +0000, Dr. David Alan Gilbert wrote: [..] > > > > @@ -1950,21 +1948,54 @@ static void lo_setlk(fuse_req_t req, fuse_i= no_t ino, > > > > =20 > > > > =09if (!plock) { > > > > =09=09saverr =3D ret; > > > > +=09=09pthread_mutex_unlock(&inode->plock_mutex); > > > > =09=09goto out; > > > > =09} > > > > =20 > > > > +=09/* > > > > +=09 * plock is now released when inode is going away. We already h= ave > > > > +=09 * a reference on inode, so it is guaranteed that plock->fd is > > > > +=09 * still around even after dropping inode->plock_mutex lock > > > > +=09 */ > > > > +=09ofd =3D plock->fd; > > > > +=09pthread_mutex_unlock(&inode->plock_mutex); > > > > + > > > > +=09/* > > > > +=09 * If this lock request can block, request caller to wait for > > > > +=09 * notification. Do not access req after this. Once lock is > > > > +=09 * available, send a notification instead. > > > > +=09 */ > > > > +=09if (sleep && lock->l_type !=3D F_UNLCK) { > > > > +=09=09/* > > > > +=09=09 * If notification queue is not enabled, can't support async > > > > +=09=09 * locks. > > > > +=09=09 */ > > > > +=09=09if (!se->notify_enabled) { > > > > +=09=09=09saverr =3D EOPNOTSUPP; > > > > +=09=09=09goto out; > > > > +=09=09} > > > > +=09=09async_lock =3D true; > > > > +=09=09unique =3D req->unique; > > > > +=09=09fuse_reply_wait(req); > > > > +=09} > > > > =09/* TODO: Is it alright to modify flock? */ > > > > =09lock->l_pid =3D 0; > > > > -=09ret =3D fcntl(plock->fd, F_OFD_SETLK, lock); > > > > +=09if (async_lock) > > > > +=09=09ret =3D fcntl(ofd, F_OFD_SETLKW, lock); > > > > +=09else > > > > +=09=09ret =3D fcntl(ofd, F_OFD_SETLK, lock); > > >=20 > > > What happens if the guest is rebooted after it's asked > > > for, but not been granted a lock? > >=20 > > I think a regular reboot can't be done till a request is pending, becau= se > > virtio-fs can't be unmounted and unmount will wait for all pending > > requests to finish. > >=20 > > Destroying qemu will destroy deamon too. > >=20 > > Are there any other reboot paths I have missed. >=20 > Yes, there are a few other ways the guest can reboot: > a) A echo b > /proc/sysrq-trigger I tried it. Both qemu and virtiofsd hang. virtiofsd wants to stop a=20 queue. And that tries to stop thrad pool. But one of the threads in thread pool is blocked on setlkw. So g_thread_pool_free() hangs. I am not seeing any option in glib thread pool API to stop or send signal to threads which are blocked. Thanks Vivek