Re: [PATCH 4/6] mkfs: fix hardlink detection in directory import code

[Christoph Hellwig <hch@lst.de>]

On Mon, Jun 29, 2026 at 06:03:41PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> There's a serious problem in the hardlink detection code in the new mkfs
> protofile functionality that copies a directory tree into the new
> filesystem.  It's been long established that hardlinks can only be
> detected by comparing st_ino *and* st_dev, but the new code doesn't do
> that.

Yes.

> Fix the detector, and stop passing struct stat objects by
> value(!) since they are quite large.

Without looking at the code I suspect the compiler silently passes
them by references as long as the functions are static, but it's
still good to fix this up.

>  static void
>  writetimestamps(
>  	struct xfs_inode	*ip,
> -	struct stat		*statbuf)
> +	const struct stat	*statbuf)

It also seems to constify a few things :)

> -	hardlink_tracker.entries[hardlink_tracker.count].src_ino = src_ino;
> +	hardlink_tracker.entries[hardlink_tracker.count].src_dev = filestat->st_dev;
> +	hardlink_tracker.entries[hardlink_tracker.count].src_ino = filestat->st_ino;
>  	hardlink_tracker.entries[hardlink_tracker.count].dst_ino = dst_ino;

A bunch of overly long lines.  This would probably benefit from
a local variable for the tracker entry.

Otherwise looks good, although I would have split it into a few patches.