From: Arnd Bergmann on
On Friday 21 May 2010, Tyler Hicks wrote:
> Lower filesystems that only implement unlocked_ioctl aren't being
> passed ioctl calls because eCryptfs only checked for
> lower_file->f_op->ioctl and returned -ENOTTY if it was NULL.
> eCryptfs shouldn't implement ioctl(), since it doesn't require the BKL.
> Instead, unlocked_ioctl() should be used and vfs_ioctl() can be called
> on the lower file since it handles locking, if necessary. This requires
> vfs_ioctl() to be exported.

Calling vfs_ioctl doesn't help you at all here, you could simply call
the ->unlocked_ioctl function of the lower fs directly to do the same,
because ->ioctl will be gone soon.

You are howevers still missing a few calls that are done through do_vfs_ioctl
or file_ioctl. To implement these, you need to add the file and super operations
that these call and forward the functions to the lower fs.

> +static long
> +ecryptfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + long rc = -ENOTTY;
> + struct file *lower_file = NULL;
> +
> + if (ecryptfs_file_to_private(file))
> + lower_file = ecryptfs_file_to_lower(file);
> + if (lower_file && lower_file->f_op && lower_file->f_op->compat_ioctl)
> + rc = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
> + return rc;
> +}
> +#endif

You need to return -ENOIOCTLCMD here, not ENOTTY to cover the case where
the lower file system does not have a ->compat_ioctl function but has its
calls listed in fs/compat_ioctl.c.

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