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Message-ID: <8734zayacu.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Tue, 19 Sep 2023 13:56:33 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Alistair Popple <apopple@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<linux-kernel@...r.kernel.org>, Bharata B Rao <bharata@....com>,
"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
Wei Xu <weixugc@...gle.com>,
"Dan Williams" <dan.j.williams@...el.com>,
Dave Hansen <dave.hansen@...el.com>,
Davidlohr Bueso <dave@...olabs.net>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Michal Hocko <mhocko@...nel.org>,
Yang Shi <shy828301@...il.com>,
Dave Jiang <dave.jiang@...el.com>,
Rafael J Wysocki <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH -V3 4/4] dax, kmem: calculate abstract distance with
general interface
Alistair Popple <apopple@...dia.com> writes:
> Huang Ying <ying.huang@...el.com> writes:
>
>> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
>> index fa1a8b418f9a..ca68ef17554b 100644
>> --- a/mm/memory-tiers.c
>> +++ b/mm/memory-tiers.c
>> @@ -586,7 +586,7 @@ EXPORT_SYMBOL_GPL(init_node_memory_type);
>> void clear_node_memory_type(int node, struct memory_dev_type *memtype)
>> {
>> mutex_lock(&memory_tier_lock);
>> - if (node_memory_types[node].memtype == memtype)
>> + if (node_memory_types[node].memtype == memtype || !memtype)
>> node_memory_types[node].map_count--;
>>
>> /*
>> * If we umapped all the attached devices to this node,
>
> This implies it's possible memtype == NULL. Yet we have this:
>
> * clear the node memory type.
> */
> if (!node_memory_types[node].map_count) {
> node_memory_types[node].memtype = NULL;
> put_memory_type(memtype);
> }
>
> It's not safe to call put_memory_type(NULL), so what condition guarantees
> map_count > 1 when called with memtype == NULL? Thanks.
Nothing guarantees that. Thanks for pointing this out. I will revise
the code to put_memory_type(node_memory_types[node].memtype) firstly.
--
Best Regards,
Huang, Ying
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