[PATCH] mm/vmalloc: fix spinning drain_vmap_work after reading from /proc/vmcore

[Christoph Hellwig]

On Tue, Apr 05, 2022 at 12:40:31PM -0700, Omar Sandoval wrote:
> A simple way to "fix" this would be to make set_iounmap_nonlazy() set
> vmap_lazy_nr to lazy_max_pages() instead of lazy_max_pages() + 1. But, I
> think it'd be better to get rid of this hack of clobbering vmap_lazy_nr.
> Instead, this fix makes __copy_oldmem_page() explicitly drain the vmap
> areas itself.

This fixes the bug and the interface also is better than what we had
before.  But a vmap/iounmap_eager would seem even better.  But hey,
right now it has one caller in always built іn x86 arch code, so maybe
it isn't worth spending more effort on this.