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Mon, 25 Nov 2019 15:44:14 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 285E222062B; Mon, 25 Nov 2019 10:44:14 -0500 (EST) Date: Mon, 25 Nov 2019 10:44:14 -0500 From: Vivek Goyal To: "Dr. David Alan Gilbert" Subject: Re: [Virtio-fs] [PATCH 4/4] virtiofsd: Implement blocking posix locks Message-ID: <20191125154414.GC13247@redhat.com> References: <20191115205543.1816-1-vgoyal@redhat.com> <20191115205543.1816-5-vgoyal@redhat.com> <20191122174732.GL2785@work-vm> MIME-Version: 1.0 In-Reply-To: <20191122174732.GL2785@work-vm> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: 98oJT-1ONmqgNt_NarwP1w-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: 207.211.31.81 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 Fri, Nov 22, 2019 at 05:47:32PM +0000, Dr. David Alan Gilbert wrote: [..] > > +static int virtio_send_notify_msg(struct fuse_session *se, struct iove= c *iov, > > +=09=09=09=09 int count) > > +{ > > + struct fv_QueueInfo *qi; > > + VuDev *dev =3D &se->virtio_dev->dev; > > + VuVirtq *q; > > + FVRequest *req; > > + VuVirtqElement *elem; > > + unsigned int in_num, bad_in_num =3D 0, bad_out_num =3D 0; > > + struct fuse_out_header *out =3D iov[0].iov_base; > > + size_t in_len, tosend_len =3D iov_size(iov, count); > > + struct iovec *in_sg; > > + int ret =3D 0; > > + > > + /* Notifications have unique =3D=3D 0 */ > > + assert (!out->unique); > > + > > + if (!se->notify_enabled) > > + return -EOPNOTSUPP; > > + > > + /* If notifications are enabled, queue index 1 is notification que= ue */ > > + qi =3D se->virtio_dev->qi[1]; > > + q =3D vu_get_queue(dev, qi->qidx); > > + > > + pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); > > + pthread_mutex_lock(&qi->vq_lock); > > + /* Pop an element from queue */ > > + req =3D vu_queue_pop(dev, q, sizeof(FVRequest), &bad_in_num, &bad_= out_num); >=20 > You don't need bad_in_num/bad_out_num - just pass NULL for both; they're > only needed if you expect to read/write data that's not mappable (i.e. > in our direct write case). Will do. [..] > > @@ -1950,21 +1948,54 @@ static void lo_setlk(fuse_req_t req, fuse_ino_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 have > > +=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? I think a regular reboot can't be done till a request is pending, because virtio-fs can't be unmounted and unmount will wait for all pending requests to finish. Destroying qemu will destroy deamon too. Are there any other reboot paths I have missed. Thanks Vivek