[PATCH v5 37/42] xfs: support idmapped mounts

[Dave Chinner]

On Tue, Jan 12, 2021 at 11:01:19PM +0100, Christian Brauner wrote:
> From: Christoph Hellwig <hch at lst.de>
> 
> Enable idmapped mounts for xfs. This basically just means passing down
> the user_namespace argument from the VFS methods down to where it is
> passed to helper.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
....
> @@ -654,6 +658,7 @@ xfs_vn_change_ok(
>   */
>  static int
>  xfs_setattr_nonsize(
> +	struct user_namespace	*mnt_userns,
>  	struct xfs_inode	*ip,
>  	struct iattr		*iattr)
>  {
> @@ -813,7 +818,7 @@ xfs_setattr_nonsize(
>  	 * 	     Posix ACL code seems to care about this issue either.
>  	 */
>  	if (mask & ATTR_MODE) {
> -		error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
> +		error = posix_acl_chmod(mnt_userns, inode, inode->i_mode);
>  		if (error)
>  			return error;
>  	}
> @@ -868,7 +873,7 @@ xfs_setattr_size(
>  		 * Use the regular setattr path to update the timestamps.
>  		 */
>  		iattr->ia_valid &= ~ATTR_SIZE;
> -		return xfs_setattr_nonsize(ip, iattr);
> +		return xfs_setattr_nonsize(&init_user_ns, ip, iattr);

Shouldn't that be passing mnt_userns?

>  	}
>  
>  	/*
> @@ -1037,6 +1042,7 @@ xfs_setattr_size(
>  
>  int
>  xfs_vn_setattr_size(
> +	struct user_namespace	*mnt_userns,
>  	struct dentry		*dentry,
>  	struct iattr		*iattr)
>  {
> @@ -1045,7 +1051,7 @@ xfs_vn_setattr_size(
>  
>  	trace_xfs_setattr(ip);
>  
> -	error = xfs_vn_change_ok(dentry, iattr);
> +	error = xfs_vn_change_ok(mnt_userns, dentry, iattr);
>  	if (error)
>  		return error;
>  	return xfs_setattr_size(ip, iattr);

And this passing mnt_userns down into xfs_setattr_size()?  Seems
like a bit of a landmine...

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com