Re: [PATCH] PM: hibernate: Drain trailing zero pages on userspace restore

[Alberto Garcia <berto@igalia.com>]

On Mon, Mar 09, 2026 at 11:01:15AM -0400, Brian Geffon wrote:
> > An alternative solution would be to do it at the beginning of
> > snapshot_write_finalize() if handle->cur > nr_meta_pages + 1.
> 
> I think this makes sense, but if snapshot_write_next() returns
> PAGE_SIZE then we need to indicate some error (eg. -ENODATA) in that
> the kernel was still expecting another copy page.

This would fail anyway in snapshot_image_loaded() because of this
condition:

   handle->cur <= nr_meta_pages + nr_copy_pages + nr_zero_pages

But I think it make sense to return an error directly from
snapshot_write_finalize() as you suggest, I can use -ENODATA.

> Also it appears that the kernel restore path and the userspace restore
> path return two different error codes for !snapshot_image_loaded(),
> the former does -ENODATA and the latter -EPERM.

Yes, -EPERM is the one that I hit in my tests.

Does this need to be corrected?

Berto