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Subject: Re: [PATCH v6 4/6] lib/dlock-list: Make sibling CPUs share the same
 linked list
To: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>, Jan Kara <jack@suse.com>,
        Jeff Layton <jlayton@poochiereds.net>,
        "J. Bruce Fields" <bfields@fieldses.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        Andi Kleen <andi@firstfloor.org>, Dave Chinner <dchinner@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>, Davidlohr Bueso <dave@stgolabs.net>,
        Waiman Long <Waiman.Long@hpe.com>
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From: Waiman Long <longman@redhat.com>
Organization: Red Hat
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Date: Thu, 5 Oct 2017 10:57:07 -0400
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On 10/05/2017 04:59 AM, Jan Kara wrote:
> On Wed 04-10-17 17:20:05, Waiman Long wrote:
>>  int alloc_dlock_list_heads(struct dlock_list_heads *dlist)
>>  {
>> -	int idx;
>> +	int idx, cnt = nr_dlock_lists ? nr_dlock_lists : nr_cpu_ids;
> Hum, is this there for the case where alloc_dlock_list_heads() is called
> before nr_dlock_lists is initialized? But how can the dlist be used later
> when it has larger number of lists and you don't know how many?

The point is nr_dlock_lists <= nr_cpu_ids. Before nr_dlock_lists is
initialized, the mapping table will map all cpus to the first entry. So
the extra entries will just stay unused. At free time, they will all get
de-allocated. I will clarify that with a comment.

Cheers,
Longman