Date:   Tue, 14 Mar 2023 10:27:25 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Baolin Wang <baolin.wang@linux.alibaba.com>
Cc:     akpm@linux-foundation.org, mgorman@techsingularity.net,
        osalvador@suse.de, vbabka@suse.cz, william.lam@bytedance.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: compaction: fix the possible deadlock when
 isolating hugetlb pages
Message-ID: <20230314172725.GA4769@monkey>
References: <1bc1c955b03603c4e14f56dfbbef9f637f18dbbd.1678703534.git.baolin.wang@linux.alibaba.com>
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 <20230313170838.GA3044@monkey>
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On 03/14/23 12:11, Baolin Wang wrote:
> On 3/14/2023 1:08 AM, Mike Kravetz wrote:
> > On 03/13/23 18:37, Baolin Wang wrote:
> > 
> > It would seem that the pfn of a hugetlb page would always be a multiple of
> > COMPACT_CLUSTER_MAX so we would drop the lock.  However, I am not sure if
> > that is ALWAYS true and would prefer something like the code you suggested.
> 
> Well, this is not always true, suppose the CONT-PTE hugetlb on ARM arch,
> which contains 16 contiguous normal pages.
> 

Right.  I keep forgetting about the CONT-* page sizes on arm :(

In any case, I think explicitly dropping the lock as you have done is a
good idea.

Feel free to add,

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
-- 
Mike Kravetz