Re: [PATCH] proc/kpageflags: add KPF_WAITERS

[Andrew Morton]

On Sun, 11 Feb 2018 13:36:41 +0300 Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> wrote:

> KPF_WAITERS indicates tasks are waiting for a page lock or writeback.
> This might be false-positive, in this case next unlock will clear it.

Well, kpageflags is full of potential false-positives.  Or do you think
this flag is especially vulnerable?

In other words, under what circumstances will we have KPF_WAITERS set
when PG_locked and PG-writeback are clear?

> This looks like worth information not only for kernel hacking.

Why?  What are the use-cases, in detail?  How are we to justify this
modification?

> In tool page-types in non-raw mode treat KPF_WAITERS without
> KPF_LOCKED and KPF_WRITEBACK as false-positive and hide it.

>  fs/proc/page.c                         |    1 +
>  include/uapi/linux/kernel-page-flags.h |    1 +
>  tools/vm/page-types.c                  |    7 +++++++

Please update Documentation/vm/pagemap.txt.