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Date:   Mon, 25 Sep 2023 23:31:40 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Hugh Dickins <hughd@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <ak@linux.intel.com>,
        Christoph Lameter <cl@linux.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        David Hildenbrand <david@redhat.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Yang Shi <shy828301@gmail.com>,
        Sidhartha Kumar <sidhartha.kumar@oracle.com>,
        Vishal Moola <vishal.moola@gmail.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Tejun Heo <tj@kernel.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Michal Hocko <mhocko@suse.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 06/12] mempolicy trivia: use pgoff_t in shared mempolicy
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 <d09b9c35-2856-f749-6a13-64dfe6415ef1@google.com>
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On Mon, Sep 25, 2023 at 01:28:14AM -0700, Hugh Dickins wrote:
> Prefer the more explicit "pgoff_t" to "unsigned long" when dealing with
> a shared mempolicy tree.  Delete confusing comment about pseudo mm vmas.

Yes, with three quibbles

>  struct sp_node {
>  	struct rb_node nd;
> -	unsigned long start, end;
> +	pgoff_t start, end;
>  	struct mempolicy *policy;
>  };
> -
>  struct shared_policy {

Did you intend to delete the blank line between these two structs?
That's not our normal style.

> +++ b/mm/mempolicy.c
> @@ -2444,7 +2444,7 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
>   * reading or for writing
>   */
>  static struct sp_node *
> -sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
> +sp_lookup(struct shared_policy *sp, pgoff_t start, pgoff_t end)

While you're reformatting anyway, mind joining these two lines?

> @@ -2499,7 +2499,7 @@ static void sp_insert(struct shared_policy *sp, struct sp_node *new)
>  
>  /* Find shared policy intersecting idx */
>  struct mempolicy *
> -mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
> +mpol_shared_policy_lookup(struct shared_policy *sp, pgoff_t idx)

Ditto