From patchwork Thu Sep 5 19:48:57 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 11133861 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6067414B4 for ; Thu, 5 Sep 2019 19:50:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21310206BB for ; Thu, 5 Sep 2019 19:50:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390470AbfIETuA (ORCPT ); Thu, 5 Sep 2019 15:50:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50886 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388426AbfIETt2 (ORCPT ); Thu, 5 Sep 2019 15:49:28 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6A6BF59451; Thu, 5 Sep 2019 19:49:27 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.137]) by smtp.corp.redhat.com (Postfix) with ESMTP id D40106012D; Thu, 5 Sep 2019 19:49:26 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 26FF12253A8; Thu, 5 Sep 2019 15:49:18 -0400 (EDT) From: Vivek Goyal To: linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, miklos@szeredi.hu Cc: linux-kernel@vger.kernel.org, virtio-fs@redhat.com, vgoyal@redhat.com, stefanha@redhat.com, dgilbert@redhat.com, mst@redhat.com Subject: [PATCH 16/18] virtiofs: Use virtio_fs_mutex for races w.r.t ->remove and mount path Date: Thu, 5 Sep 2019 15:48:57 -0400 Message-Id: <20190905194859.16219-17-vgoyal@redhat.com> In-Reply-To: <20190905194859.16219-1-vgoyal@redhat.com> References: <20190905194859.16219-1-vgoyal@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 05 Sep 2019 19:49:27 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org It is possible that a mount is in progress and device is being removed at the same time. Use virtio_fs_mutex to avoid races. This also takes care of bunch of races and removes some TODO items. Signed-off-by: Vivek Goyal Reviewed-by: Stefan Hajnoczi Signed-off-by: Vivek Goyal Reviewed-by: Stefan Hajnoczi --- fs/fuse/virtio_fs.c | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c index 29ec2f5bbbe2..c483482185b6 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -13,7 +13,9 @@ #include #include "fuse_i.h" -/* List of virtio-fs device instances and a lock for the list */ +/* List of virtio-fs device instances and a lock for the list. Also provides + * mutual exclusion in device removal and mounting path + */ static DEFINE_MUTEX(virtio_fs_mutex); static LIST_HEAD(virtio_fs_instances); @@ -72,17 +74,19 @@ static void release_virtiofs_obj(struct kref *ref) kfree(vfs); } +/* Make sure virtiofs_mutex is held */ static void virtiofs_put(struct virtio_fs *fs) { - mutex_lock(&virtio_fs_mutex); kref_put(&fs->refcount, release_virtiofs_obj); - mutex_unlock(&virtio_fs_mutex); } static void virtio_fs_put(struct fuse_iqueue *fiq) { struct virtio_fs *vfs = fiq->priv; + + mutex_lock(&virtio_fs_mutex); virtiofs_put(vfs); + mutex_unlock(&virtio_fs_mutex); } static void virtio_fs_drain_queue(struct virtio_fs_vq *fsvq) @@ -596,9 +600,8 @@ static void virtio_fs_remove(struct virtio_device *vdev) struct virtio_fs *fs = vdev->priv; mutex_lock(&virtio_fs_mutex); + /* This device is going away. No one should get new reference */ list_del_init(&fs->list); - mutex_unlock(&virtio_fs_mutex); - virtio_fs_stop_all_queues(fs); virtio_fs_drain_all_queues(fs); vdev->config->reset(vdev); @@ -607,6 +610,7 @@ static void virtio_fs_remove(struct virtio_device *vdev) vdev->priv = NULL; /* Put device reference on virtio_fs object */ virtiofs_put(fs); + mutex_unlock(&virtio_fs_mutex); } #ifdef CONFIG_PM_SLEEP @@ -978,10 +982,15 @@ static int virtio_fs_fill_super(struct super_block *sb) .no_force_umount = true, }; - /* TODO lock */ - if (fs->vqs[VQ_REQUEST].fud) { - pr_err("virtio-fs: device already in use\n"); - err = -EBUSY; + mutex_lock(&virtio_fs_mutex); + + /* After holding mutex, make sure virtiofs device is still there. + * Though we are holding a refernce to it, drive ->remove might + * still have cleaned up virtual queues. In that case bail out. + */ + err = -EINVAL; + if (list_empty(&fs->list)) { + pr_info("virtio-fs: tag <%s> not found\n", fs->tag); goto err; } @@ -1007,7 +1016,6 @@ static int virtio_fs_fill_super(struct super_block *sb) fc = fs->vqs[VQ_REQUEST].fud->fc; - /* TODO take fuse_mutex around this loop? */ for (i = 0; i < fs->nvqs; i++) { struct virtio_fs_vq *fsvq = &fs->vqs[i]; @@ -1020,6 +1028,7 @@ static int virtio_fs_fill_super(struct super_block *sb) /* Previous unmount will stop all queues. Start these again */ virtio_fs_start_all_queues(fs); fuse_send_init(fc, init_req); + mutex_unlock(&virtio_fs_mutex); return 0; err_free_init_req: @@ -1027,6 +1036,7 @@ static int virtio_fs_fill_super(struct super_block *sb) err_free_fuse_devs: virtio_fs_free_devs(fs); err: + mutex_unlock(&virtio_fs_mutex); return err; } @@ -1100,7 +1110,9 @@ static int virtio_fs_get_tree(struct fs_context *fsc) fc = kzalloc(sizeof(struct fuse_conn), GFP_KERNEL); if (!fc) { + mutex_lock(&virtio_fs_mutex); virtiofs_put(fs); + mutex_unlock(&virtio_fs_mutex); return -ENOMEM; }