[PATCH] mount: rebuild error handling in do_new_mount

[PATCH] mount: rebuild error handling in do_new_mount

[Chuang Wang]

When a function execution error is detected in do_new_mount, it should
return immediately. Using this can make the code easier to understand.

Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
---
 fs/namespace.c | 53 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 34 insertions(+), 19 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index ab467ee58341..a544e814b326 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3116,36 +3116,51 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
 	if (!type)
 		return -ENODEV;
 
+	fc = fs_context_for_mount(type, sb_flags);
+	put_filesystem(type);
+	if (IS_ERR(fc))
+		return PTR_ERR(fc);
+
+	/* subtype */
 	if (type->fs_flags & FS_HAS_SUBTYPE) {
 		subtype = strchr(fstype, '.');
 		if (subtype) {
 			subtype++;
 			if (!*subtype) {
-				put_filesystem(type);
-				return -EINVAL;
+				err = -EINVAL;
+				goto err_fc;
 			}
+
+			err = vfs_parse_fs_string(fc, "subtype",
+						  subtype, strlen(subtype));
+			if (err)
+				goto err_fc;
 		}
 	}
 
-	fc = fs_context_for_mount(type, sb_flags);
-	put_filesystem(type);
-	if (IS_ERR(fc))
-		return PTR_ERR(fc);
-
-	if (subtype)
-		err = vfs_parse_fs_string(fc, "subtype",
-					  subtype, strlen(subtype));
-	if (!err && name)
+	/* source */
+	if (name) {
 		err = vfs_parse_fs_string(fc, "source", name, strlen(name));
-	if (!err)
-		err = parse_monolithic_mount_data(fc, data);
-	if (!err && !mount_capable(fc))
-		err = -EPERM;
-	if (!err)
-		err = vfs_get_tree(fc);
-	if (!err)
-		err = do_new_mount_fc(fc, path, mnt_flags);
+		if (err)
+			goto err_fc;
+	}
+
+	/* monolithic data */
+	err = parse_monolithic_mount_data(fc, data);
+	if (err)
+		goto err_fc;
+
+	err = -EPERM;
+	if (!mount_capable(fc))
+		goto err_fc;
+
+	err = vfs_get_tree(fc);
+	if (err)
+		goto err_fc;
+
+	err = do_new_mount_fc(fc, path, mnt_flags);
 
+err_fc:
 	put_fs_context(fc);
 	return err;
 }
-- 
2.37.2

Re: [PATCH] mount: rebuild error handling in do_new_mount

[Al Viro]

On Sun, Dec 04, 2022 at 11:00:05PM +0800, Chuang Wang wrote:
> When a function execution error is detected in do_new_mount, it should
> return immediately. Using this can make the code easier to understand.

Your piles of goto make it harder to follow and reason about.

NAKed-by: Al Viro <viro@zeniv.linux.org.uk>