fix sget / sget_fc thrashing on sb_lock

gistfile1.txt

diff --git a/fs/super.c b/fs/super.c
index 59bbbd8a6..e029eb3f6 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -566,6 +566,7 @@ struct super_block *sget_fc(struct fs_context *fc,
 	struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
 	int err;
 
+	s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
@@ -576,10 +577,7 @@ struct super_block *sget_fc(struct fs_context *fc,
 	}
 	if (!s) {
 		spin_unlock(&sb_lock);
-		s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
-		if (!s)
-			return ERR_PTR(-ENOMEM);
-		goto retry;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	s->s_fs_info = fc->s_fs_info;
@@ -640,6 +638,7 @@ struct super_block *sget(struct file_system_type *type,
 	if (flags & SB_SUBMOUNT)
 		user_ns = &init_user_ns;
 
+	s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
@@ -659,10 +658,7 @@ struct super_block *sget(struct file_system_type *type,
 	}
 	if (!s) {
 		spin_unlock(&sb_lock);
-		s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
-		if (!s)
-			return ERR_PTR(-ENOMEM);
-		goto retry;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	err = set(s, data);