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Subject: Re: [PATCH] mm: Simplify and batch working set shadow pages LRU
 isolation locking
References: <20171026234854.25764-1-andi@firstfloor.org>
 <20171027170156.GA1743@cmpxchg.org>
 <20171027172205.GA22894@tassilo.jf.intel.com>
From: Daniel Jordan <daniel.m.jordan@oracle.com>
Message-ID: <cf74ed09-7478-7047-ccb1-d2847499585e@oracle.com>
Date: Fri, 27 Oct 2017 16:59:16 -0400
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To: Andi Kleen <ak@linux.intel.com>, Johannes Weiner <hannes@cmpxchg.org>
Cc: Andi Kleen <andi@firstfloor.org>, akpm@linux-foundation.org, linux-mm@kvack.org

On 10/27/2017 01:22 PM, Andi Kleen wrote:
>> The nlru->lock in list_lru_shrink_walk() is the only thing that keeps
>> truncation blocked on workingset_update_node() -> list_lru_del() and
>> so ultimately keeping it from freeing the radix tree node.
>>
>> It's not safe to access the nodes on the private list after that.
> True.
>
>> Batching mapping->tree_lock is possible, but you have to keep the
>> lock-handoff scheme. Pass a &mapping to list_lru_shrink_walk() and
>> only unlock and spin_trylock(&mapping->tree_lock) if it changes?
> Yes something like that could work. Thanks.

My mistake, I didn't see this other thread and clearly missed this issue.

Daniel

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