Re: [PATCH v2] mm/memory-failure: Support disabling soft offline for HugeTLB pages

Luck, Tony
2025-09-17T19:54:17Z

On Wed, Sep 17, 2025 at 12:32:47PM -0700, Jiaqi Yan wrote:
> +1. Given /proc/sys/vm/enable_soft_offline is extensible, I would
> prefer a compact userspace API.
>
> > would create a new file, and the file has weird semantics such that it
> > has no meaning when enable_soft_offline=0.

So the expand the bitmask idea from earlier in this thread?

Bit0 0 = soft offline disabled. 1 = Enabled (but see other bits)
Bit1 0 = allow offline of 4K pages, 1 = suppress 4K offline
Bit2 0 = allow offline of hugetlb, 1 = suppress hugetlb offline
Bit3 0 = allow breakup of transparent huge pages to just offline 4K, 1 = suppress transparent breakup
Bit4+ Reserved for suppressing other page types we invent in the future

Values 0 and 1 keep their original meaning.

Value 5 means: offline 4K, keep hugetlb, breakup transparent huge pages.

-Tony