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Date:   Mon, 16 Aug 2021 17:39:59 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        David Hildenbrand <david@redhat.com>,
        Michal Hocko <mhocko@suse.com>,
        Oscar Salvador <osalvador@suse.de>, Zi Yan <ziy@nvidia.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Naoya Horiguchi <naoya.horiguchi@linux.dev>,
        David Rientjes <rientjes@google.com>
Subject: Re: [PATCH RESEND 0/8] hugetlb: add demote/split page functionality
Message-Id: <20210816173959.950443c7516a2b178e2ec376@linux-foundation.org>
In-Reply-To: <5dd4e07b-d2cf-63f2-fc0a-9b371b469a44@oracle.com>
References: <20210816224953.157796-1-mike.kravetz@oracle.com>
        <20210816162305.b19bfa3f3ba7431a62ff205f@linux-foundation.org>
        <5dd4e07b-d2cf-63f2-fc0a-9b371b469a44@oracle.com>
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On Mon, 16 Aug 2021 17:17:50 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:

> > 
> > And how does one know the operation has completed so the sysfs files
> > can be reloaded for another operation?
> > 
> 
> When the write to the file is complete, the operation has completed.
> Not exactly sure what you mean by reloading the sysfs files for
> another operation?

If userspace wishes to perform another demote operation, it must wait
for the preceding one to complete.

Presumably if thread A is blocked in a write to `demote' and thread B
concurrently tries to perform a demotion, thread B will be blocked as
well?  Was this tested?

Lots of things are to be added to changelogs & documentation, methinks.