(2012/06/21 20:48), Liu Bo wrote:
> $ 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@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/ioctl.c | 27 ++++++++++++++++++---------
> 1 files changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index df4c04d..ae29737 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1519,29 +1519,35 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
> 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;
>
> + ret = -EINVAL;
> if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID)
> - return -EINVAL;
> + goto out_drop_write;
>
> + ret = -EFAULT;
> if (copy_from_user(&flags, arg, sizeof(flags)))
> - return -EFAULT;
> + goto out_drop_write;
>
> + ret = -EINVAL;
> if (flags & BTRFS_SUBVOL_CREATE_ASYNC)
> - return -EINVAL;
> + goto out_drop_write;
>
> + ret = -EOPNOTSUPP;
> if (flags & ~BTRFS_SUBVOL_RDONLY)
> - return -EOPNOTSUPP;
> + goto out_drop_write;
>
> + ret = -EACCES;
> if (!inode_owner_or_capable(inode))
> - return -EACCES;
> + goto out_drop_write;
I think that
if (!inode_owner_or_capable(inode)) {
ret = -EACCES;
goto out_drop_write;
}
is better than
ret = -EACCES;
if (!inode_owner_or_capable(inode))
goto out_drop_write;
Thanks,
Tsutomu
>
> 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)
> @@ -1564,8 +1570,11 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
> 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;
> }
>
>
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