Otherwise lockdep says:

[ 1337.483798] ================================================
[ 1337.483999] [ BUG: lock held when returning to user space! ]
[ 1337.484252] 4.11.0-rc6 #19 Not tainted
[ 1337.484423] ------------------------------------------------
[ 1337.484626] mount/14766 is leaving the kernel with locks still held!
[ 1337.484841] 1 lock held by mount/14766:
[ 1337.485017]  #0:  (&type->s_umount_key#33/1){+.+.+.}, at: 
[<ffffffff8124171f>] sget_userns+0x2af/0x520

Caught by xfstests generic/413 which tried to mount with the unsupported
mount option dax.  Then xfstests generic/422 ran sync which deadlocks.

Signed-off-by: Martin Brandenburg <mar...@omnibond.com>
Cc: sta...@vger.kernel.org
---
 fs/orangefs/devorangefs-req.c |  9 +++++++--
 fs/orangefs/orangefs-kernel.h |  1 +
 fs/orangefs/super.c           | 23 ++++++++++++++++-------
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/fs/orangefs/devorangefs-req.c b/fs/orangefs/devorangefs-req.c
index c4ab6fdf17a0..e1534c9bab16 100644
--- a/fs/orangefs/devorangefs-req.c
+++ b/fs/orangefs/devorangefs-req.c
@@ -208,14 +208,19 @@ static ssize_t orangefs_devreq_read(struct file *file,
                                continue;
                        /*
                         * Skip ops whose filesystem we don't know about unless
-                        * it is being mounted.
+                        * it is being mounted or unmounted.  It is possible for
+                        * a filesystem we don't know about to be unmounted if
+                        * it fails to mount in the kernel after userspace has
+                        * been sent the mount request.
                         */
                        /* XXX: is there a better way to detect this? */
                        } else if (ret == -1 &&
                                   !(op->upcall.type ==
                                        ORANGEFS_VFS_OP_FS_MOUNT ||
                                     op->upcall.type ==
-                                       ORANGEFS_VFS_OP_GETATTR)) {
+                                       ORANGEFS_VFS_OP_GETATTR ||
+                                    op->upcall.type ==
+                                       ORANGEFS_VFS_OP_FS_UMOUNT)) {
                                gossip_debug(GOSSIP_DEV_DEBUG,
                                    "orangefs: skipping op tag %llu %s\n",
                                    llu(op->tag), get_opname_string(op));
diff --git a/fs/orangefs/orangefs-kernel.h b/fs/orangefs/orangefs-kernel.h
index 5e48a0be9761..8afac46fcc87 100644
--- a/fs/orangefs/orangefs-kernel.h
+++ b/fs/orangefs/orangefs-kernel.h
@@ -249,6 +249,7 @@ struct orangefs_sb_info_s {
        char devname[ORANGEFS_MAX_SERVER_ADDR_LEN];
        struct super_block *sb;
        int mount_pending;
+       int no_list;
        struct list_head list;
 };
 
diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
index cd261c8de53a..629d8c917fa6 100644
--- a/fs/orangefs/super.c
+++ b/fs/orangefs/super.c
@@ -493,7 +493,7 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
 
        if (ret) {
                d = ERR_PTR(ret);
-               goto free_op;
+               goto free_sb_and_op;
        }
 
        /*
@@ -519,6 +519,9 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
        spin_unlock(&orangefs_superblocks_lock);
        op_release(new_op);
 
+       /* Must be removed from the list now. */
+       ORANGEFS_SB(sb)->no_list = 0;
+
        if (orangefs_userspace_version >= 20906) {
                new_op = op_alloc(ORANGEFS_VFS_OP_FEATURES);
                if (!new_op)
@@ -533,6 +536,10 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
 
        return dget(sb->s_root);
 
+free_sb_and_op:
+       /* Will call orangefs_kill_sb with sb not in list. */
+       ORANGEFS_SB(sb)->no_list = 1;
+       deactivate_locked_super(sb);
 free_op:
        gossip_err("orangefs_mount: mount request failed with %d\n", ret);
        if (ret == -EINVAL) {
@@ -558,12 +565,14 @@ void orangefs_kill_sb(struct super_block *sb)
         */
         orangefs_unmount_sb(sb);
 
-       /* remove the sb from our list of orangefs specific sb's */
-
-       spin_lock(&orangefs_superblocks_lock);
-       __list_del_entry(&ORANGEFS_SB(sb)->list);       /* not list_del_init */
-       ORANGEFS_SB(sb)->list.prev = NULL;
-       spin_unlock(&orangefs_superblocks_lock);
+       if (!ORANGEFS_SB(sb)->no_list) {
+               /* remove the sb from our list of orangefs specific sb's */
+               spin_lock(&orangefs_superblocks_lock);
+               /* not list_del_init */
+               __list_del_entry(&ORANGEFS_SB(sb)->list);
+               ORANGEFS_SB(sb)->list.prev = NULL;
+               spin_unlock(&orangefs_superblocks_lock);
+       }
 
        /*
         * make sure that ORANGEFS_DEV_REMOUNT_ALL loop that might've seen us
-- 
2.11.0

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