Merge tag 'fuse-update-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse updates from Miklos Szeredi:

 - Fix an issue with reusing the bdi in case of block based filesystems

 - Allow root (in init namespace) to access fuse filesystems in user
   namespaces if expicitly enabled with a module param

 - Misc fixes

* tag 'fuse-update-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: retire block-device-based superblock on force unmount
  vfs: function to prevent re-use of block-device-based superblocks
  virtio_fs: Modify format for virtio_fs_direct_access
  virtiofs: delete unused parameter for virtio_fs_cleanup_vqs
  fuse: Add module param for CAP_SYS_ADMIN access bypassing allow_other
  fuse: Remove the control interface for virtio-fs
  fuse: ioctl: translate ENOSYS
  fuse: limit nsec
  fuse: avoid unnecessary spinlock bump
  fuse: fix deadlock between atomic O_TRUNC and page invalidation
  fuse: write inode in fuse_release()

1 files changed, 31 insertions, 2 deletions

diff --git a/fs/super.c b/fs/super.c
index 4fca6657f442..734ed584a946 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -423,6 +423,35 @@ bool trylock_super(struct super_block *sb)
 }
 
 /**
+ *	retire_super	-	prevents superblock from being reused
+ *	@sb: superblock to retire
+ *
+ *	The function marks superblock to be ignored in superblock test, which
+ *	prevents it from being reused for any new mounts.  If the superblock has
+ *	a private bdi, it also unregisters it, but doesn't reduce the refcount
+ *	of the superblock to prevent potential races.  The refcount is reduced
+ *	by generic_shutdown_super().  The function can not be called
+ *	concurrently with generic_shutdown_super().  It is safe to call the
+ *	function multiple times, subsequent calls have no effect.
+ *
+ *	The marker will affect the re-use only for block-device-based
+ *	superblocks.  Other superblocks will still get marked if this function
+ *	is used, but that will not affect their reusability.
+ */
+void retire_super(struct super_block *sb)
+{
+	WARN_ON(!sb->s_bdev);
+	down_write(&sb->s_umount);
+	if (sb->s_iflags & SB_I_PERSB_BDI) {
+		bdi_unregister(sb->s_bdi);
+		sb->s_iflags &= ~SB_I_PERSB_BDI;
+	}
+	sb->s_iflags |= SB_I_RETIRED;
+	up_write(&sb->s_umount);
+}
+EXPORT_SYMBOL(retire_super);
+
+/**
  *	generic_shutdown_super	-	common helper for ->kill_sb()
  *	@sb: superblock to kill
  *
@@ -1216,7 +1245,7 @@ static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
 
 static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
 {
-	return s->s_bdev == fc->sget_key;
+	return !(s->s_iflags & SB_I_RETIRED) && s->s_bdev == fc->sget_key;
 }
 
 /**
@@ -1309,7 +1338,7 @@ EXPORT_SYMBOL(get_tree_bdev);
 
 static int test_bdev_super(struct super_block *s, void *data)
 {
-	return (void *)s->s_bdev == data;
+	return !(s->s_iflags & SB_I_RETIRED) && (void *)s->s_bdev == data;
 }
 
 struct dentry *mount_bdev(struct file_system_type *fs_type,