1 files changed, 32 insertions, 32 deletions

diff --git a/fs/super.c b/fs/super.c
index ef87103e2a51..692654c2af36 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -736,17 +736,31 @@ bool mount_capable(struct fs_context *fc)
  * @test: Comparison callback
  * @set: Setup callback
  *
- * Find or create a superblock using the parameters stored in the filesystem
- * context and the two callback functions.
+ * Create a new superblock or find an existing one.
  *
- * If an extant superblock is matched, then that will be returned with an
- * elevated reference count that the caller must transfer or discard.
+ * The @test callback is used to find a matching existing superblock.
+ * Whether or not the requested parameters in @fc are taken into account
+ * is specific to the @test callback that is used. They may even be
+ * completely ignored.
+ *
+ * If an extant superblock is matched, it will be returned unless:
+ *
+ * (1) the namespace the filesystem context @fc and the extant
+ *     superblock's namespace differ
+ *
+ * (2) the filesystem context @fc has requested that reusing an extant
+ *     superblock is not allowed
+ *
+ * In both cases EBUSY will be returned.
  *
  * If no match is made, a new superblock will be allocated and basic
- * initialisation will be performed (s_type, s_fs_info and s_id will be set and
- * the set() callback will be invoked), the superblock will be published and it
- * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
- * as yet unset.
+ * initialisation will be performed (s_type, s_fs_info and s_id will be
+ * set and the @set callback will be invoked), the superblock will be
+ * published and it will be returned in a partially constructed state
+ * with SB_BORN and SB_ACTIVE as yet unset.
+ *
+ * Return: On success, an extant or newly created superblock is
+ *         returned. On failure an error pointer is returned.
  */
 struct super_block *sget_fc(struct fs_context *fc,
 			    int (*test)(struct super_block *, struct fs_context *),
@@ -798,9 +812,13 @@ retry:
 	return s;
 
 share_extant_sb:
-	if (user_ns != old->s_user_ns) {
+	if (user_ns != old->s_user_ns || fc->exclusive) {
 		spin_unlock(&sb_lock);
 		destroy_unused_super(s);
+		if (fc->exclusive)
+			warnfc(fc, "reusing existing filesystem not allowed");
+		else
+			warnfc(fc, "reusing existing filesystem in another namespace not allowed");
 		return ERR_PTR(-EBUSY);
 	}
 	if (!grab_super_dead(old))
@@ -1288,7 +1306,7 @@ static int test_single_super(struct super_block *s, struct fs_context *fc)
 	return 1;
 }
 
-static int vfs_get_super(struct fs_context *fc, bool reconf,
+static int vfs_get_super(struct fs_context *fc,
 		int (*test)(struct super_block *, struct fs_context *),
 		int (*fill_super)(struct super_block *sb,
 				  struct fs_context *fc))
@@ -1306,19 +1324,9 @@ static int vfs_get_super(struct fs_context *fc, bool reconf,
 			goto error;
 
 		sb->s_flags |= SB_ACTIVE;
-		fc->root = dget(sb->s_root);
-	} else {
-		fc->root = dget(sb->s_root);
-		if (reconf) {
-			err = reconfigure_super(fc);
-			if (err < 0) {
-				dput(fc->root);
-				fc->root = NULL;
-				goto error;
-			}
-		}
 	}
 
+	fc->root = dget(sb->s_root);
 	return 0;
 
 error:
@@ -1330,7 +1338,7 @@ int get_tree_nodev(struct fs_context *fc,
 		  int (*fill_super)(struct super_block *sb,
 				    struct fs_context *fc))
 {
-	return vfs_get_super(fc, false, NULL, fill_super);
+	return vfs_get_super(fc, NULL, fill_super);
 }
 EXPORT_SYMBOL(get_tree_nodev);
 
@@ -1338,25 +1346,17 @@ int get_tree_single(struct fs_context *fc,
 		  int (*fill_super)(struct super_block *sb,
 				    struct fs_context *fc))
 {
-	return vfs_get_super(fc, false, test_single_super, fill_super);
+	return vfs_get_super(fc, test_single_super, fill_super);
 }
 EXPORT_SYMBOL(get_tree_single);
 
-int get_tree_single_reconf(struct fs_context *fc,
-		  int (*fill_super)(struct super_block *sb,
-				    struct fs_context *fc))
-{
-	return vfs_get_super(fc, true, test_single_super, fill_super);
-}
-EXPORT_SYMBOL(get_tree_single_reconf);
-
 int get_tree_keyed(struct fs_context *fc,
 		  int (*fill_super)(struct super_block *sb,
 				    struct fs_context *fc),
 		void *key)
 {
 	fc->s_fs_info = key;
-	return vfs_get_super(fc, false, test_keyed_super, fill_super);
+	return vfs_get_super(fc, test_keyed_super, fill_super);
 }
 EXPORT_SYMBOL(get_tree_keyed);