Btrfs: clean up error handling in mount_subvol()

In preparation for new functionality in mount_subvol(), give it
ownership of subvol_name and tidy up the error paths.

Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 1c57c0d0dc41ba723ec45d1f92ea5f30e88866df..dd89dd353c4ae84154dd8975d8cffdaa744e1aad 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1171,55 +1171,61 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags,
                                   const char *device_name, char *data)
 {
        struct dentry *root;
-       struct vfsmount *mnt;
+       struct vfsmount *mnt = NULL;
        char *newargs;
+       int ret;
 
        newargs = setup_root_args(data);
-       if (!newargs)
-               return ERR_PTR(-ENOMEM);
-       mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
-                            newargs);
+       if (!newargs) {
+               root = ERR_PTR(-ENOMEM);
+               goto out;
+       }
 
-       if (PTR_RET(mnt) == -EBUSY) {
+       mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name, newargs);
+       if (PTR_ERR_OR_ZERO(mnt) == -EBUSY) {
                if (flags & MS_RDONLY) {
-                       mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY, device_name,
-                                            newargs);
+                       mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY,
+                                            device_name, newargs);
                } else {
-                       int r;
-                       mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY, device_name,
-                                            newargs);
+                       mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY,
+                                            device_name, newargs);
                        if (IS_ERR(mnt)) {
-                               kfree(newargs);
-                               return ERR_CAST(mnt);
+                               root = ERR_CAST(mnt);
+                               mnt = NULL;
+                               goto out;
                        }
 
                        down_write(&mnt->mnt_sb->s_umount);
-                       r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
+                       ret = btrfs_remount(mnt->mnt_sb, &flags, NULL);
                        up_write(&mnt->mnt_sb->s_umount);
-                       if (r < 0) {
-                               /* FIXME: release vfsmount mnt ??*/
-                               kfree(newargs);
-                               return ERR_PTR(r);
+                       if (ret < 0) {
+                               root = ERR_PTR(ret);
+                               goto out;
                        }
                }
        }
-
-       kfree(newargs);
-
-       if (IS_ERR(mnt))
-               return ERR_CAST(mnt);
+       if (IS_ERR(mnt)) {
+               root = ERR_CAST(mnt);
+               mnt = NULL;
+               goto out;
+       }
 
        root = mount_subtree(mnt, subvol_name);
+       /* mount_subtree() drops our reference on the vfsmount. */
+       mnt = NULL;
 
        if (!IS_ERR(root) && !is_subvolume_inode(d_inode(root))) {
                struct super_block *s = root->d_sb;
                dput(root);
                root = ERR_PTR(-EINVAL);
                deactivate_locked_super(s);
-               printk(KERN_ERR "BTRFS: '%s' is not a valid subvolume\n",
-                               subvol_name);
+               pr_err("BTRFS: '%s' is not a valid subvolume\n", subvol_name);
        }
 
+out:
+       mntput(mnt);
+       kfree(newargs);
+       kfree(subvol_name);
        return root;
 }
 
@@ -1305,9 +1311,8 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
        }
 
        if (subvol_name) {
-               root = mount_subvol(subvol_name, flags, device_name, data);
-               kfree(subvol_name);
-               return root;
+               /* mount_subvol() will free subvol_name. */
+               return mount_subvol(subvol_name, flags, device_name, data);
        }
 
        security_init_mnt_opts(&new_sec_opts);