Fix deletion of ReparsePoints that aren't mountpoints

rmdir of junctions should be allowed, but we do want to
stop the mountpoints from being deleted (without unmounting)
and that test was too coarse. Now we only prohibit removal
of mountpoints.

Signed-off-by: Jorgen Lundman <lundman@lundman.net>

Author: lundman

include/os/windows/spl/sys/mount.h

@@ -176,6 +176,7 @@ void vfs_mount_iterate(int (*func)(void *, void *), void *);
 boolean_t vfs_mount_member(void *member);
 void vfs_set_mountedon(mount_t *mp, char *rootpath);
 const char *vfs_mountedon(mount_t *mp);
+mount_t *vfs_has_mount(const char *rpath);
 
 
 #endif /* SPL_MOUNT_H */

module/os/windows/spl/spl-mount.c

@@ -296,3 +296,23 @@ vfs_mountedon(mount_t *mp)
 {
 	return (mp->mounted_on ? mp->mounted_on : "\\");
 }
+
+mount_t *
+vfs_has_mount(const char *rpath)
+{
+	int count = 0;
+	mount_t *node;
+
+	mutex_enter(&mount_list_lock);
+	for (node = list_head(&mount_list);
+	    node;
+	    node = list_next(&mount_list, node)) {
+		if (rpath && node->mounted_on &&
+		    strcmp(rpath, node->mounted_on) == 0) {
+			mutex_exit(&mount_list_lock);
+			return (node);
+		}
+	}
+	mutex_exit(&mount_list_lock);
+	return (NULL);
+}

module/os/windows/zfs/zfs_vnops_windows.c

@@ -4237,6 +4237,17 @@ delete_reparse_point(PDEVICE_OBJECT DeviceObject, PIRP Irp,
 		return (STATUS_INVALID_PARAMETER);
 
 	znode_t *zp = VTOZ(vp);
+	zfs_ccb_t *zccb = FileObject->FsContext2;
+
+	// Is something mounted on here? We deny it, so that
+	// it has to be unmounted by us first. We will remove
+	// from list of mounts, before deleting reparse point
+	if (zccb &&
+	    vfs_has_mount(zccb->z_name_cache)) {
+		dprintf("Denied due to being mountpoint\n");
+		VN_RELE(vp);
+		return (STATUS_CANNOT_DELETE);
+	}
 
 	if (zfsctl_is_node(zp)) {
 		VN_RELE(vp);

module/os/windows/zfs/zfs_vnops_windows_lib.c

@@ -3447,10 +3447,10 @@ zfs_setunlink(FILE_OBJECT *fo, vnode_t *dvp)
 		goto out;
 	}
 
-	// Stopping reparsepoints in use, for now.
-	// Force them to call DELETE_REPARSE_POINT first
-	if ((zp->z_pflags & ZFS_REPARSE) /* && vnode_isinuse(vp, 0) */) {
-		Status = STATUS_CANNOT_DELETE;
+	// If it is a reparsepoint, deny if used as mountpoint
+	if ((zp->z_pflags & ZFS_REPARSE) && zccb &&
+	    vfs_has_mount(zccb->z_name_cache)) {
+		Status = STATUS_ACCESS_DENIED;
 		goto out;
 	}
 

module/os/windows/zfs/zfs_vnops_windows_mount.c

@@ -2264,6 +2264,11 @@ zfs_windows_unmount(zfs_cmd_t *zc)
 
 		} else {
 			// If mount uses reparsepoint (not driveletter)
+			// To let delete reparse point to succeed, the
+			// vfs_is_mountpoint() need to fail, so free the
+			// root mountpoint it uses.
+			vfs_set_mountedon(zmo, NULL);
+
 			OBJECT_ATTRIBUTES poa;
 
 			InitializeObjectAttributes(&poa,