Btrfs: do not set subvolume flags in readonly mode
$ mkfs.btrfs /dev/sdb7
$ btrfstune -S1 /dev/sdb7
$ mount /dev/sdb7 /mnt/btrfs
mount: block device /dev/sdb7 is write-protected, mounting read-only
$ btrfs dev add /dev/sdb8 /mnt/btrfs/
Now we get a btrfs in which mnt flags has readonly but sb flags does
not. So for those ioctls that only check sb flags with MS_RDONLY, it
is going to be a problem.
Setting subvolume flags is such an ioctl, we should use mnt_want_write_file()
to check RO flags.
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 13ed1c9..17facea 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1521,29 +1521,40 @@
u64 flags;
int ret = 0;
- if (root->fs_info->sb->s_flags & MS_RDONLY)
- return -EROFS;
+ ret = mnt_want_write_file(file);
+ if (ret)
+ goto out;
- if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID)
- return -EINVAL;
+ if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {
+ ret = -EINVAL;
+ goto out_drop_write;
+ }
- if (copy_from_user(&flags, arg, sizeof(flags)))
- return -EFAULT;
+ if (copy_from_user(&flags, arg, sizeof(flags))) {
+ ret = -EFAULT;
+ goto out_drop_write;
+ }
- if (flags & BTRFS_SUBVOL_CREATE_ASYNC)
- return -EINVAL;
+ if (flags & BTRFS_SUBVOL_CREATE_ASYNC) {
+ ret = -EINVAL;
+ goto out_drop_write;
+ }
- if (flags & ~BTRFS_SUBVOL_RDONLY)
- return -EOPNOTSUPP;
+ if (flags & ~BTRFS_SUBVOL_RDONLY) {
+ ret = -EOPNOTSUPP;
+ goto out_drop_write;
+ }
- if (!inode_owner_or_capable(inode))
- return -EACCES;
+ if (!inode_owner_or_capable(inode)) {
+ ret = -EACCES;
+ goto out_drop_write;
+ }
down_write(&root->fs_info->subvol_sem);
/* nothing to do */
if (!!(flags & BTRFS_SUBVOL_RDONLY) == btrfs_root_readonly(root))
- goto out;
+ goto out_drop_sem;
root_flags = btrfs_root_flags(&root->root_item);
if (flags & BTRFS_SUBVOL_RDONLY)
@@ -1566,8 +1577,11 @@
out_reset:
if (ret)
btrfs_set_root_flags(&root->root_item, root_flags);
-out:
+out_drop_sem:
up_write(&root->fs_info->subvol_sem);
+out_drop_write:
+ mnt_drop_write_file(file);
+out:
return ret;
}