linux-kernel - [PATCH 06/12] mempolicy trivia: use pgoff

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Date:   Mon, 25 Sep 2023 01:28:14 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Andi Kleen <ak@...ux.intel.com>, Christoph Lameter <cl@...ux.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Vishal Moola <vishal.moola@...il.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH 06/12] mempolicy trivia: use pgoff_t in shared mempolicy
 tree

Prefer the more explicit "pgoff_t" to "unsigned long" when dealing with
a shared mempolicy tree.  Delete confusing comment about pseudo mm vmas.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 include/linux/mempolicy.h | 12 +++---------
 mm/mempolicy.c            |  8 ++++----
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 8013d716dc46..12f7dc74a457 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -107,18 +107,12 @@ static inline bool mpol_equal(struct mempolicy *a, struct mempolicy *b)
 
 /*
  * Tree of shared policies for a shared memory region.
- * Maintain the policies in a pseudo mm that contains vmas. The vmas
- * carry the policy. As a special twist the pseudo mm is indexed in pages, not
- * bytes, so that we can work with shared memory segments bigger than
- * unsigned long.
  */
-
 struct sp_node {
 	struct rb_node nd;
-	unsigned long start, end;
+	pgoff_t start, end;
 	struct mempolicy *policy;
 };
-
 struct shared_policy {
 	struct rb_root root;
 	rwlock_t lock;
@@ -130,7 +124,7 @@ int mpol_set_shared_policy(struct shared_policy *sp,
 			   struct vm_area_struct *vma, struct mempolicy *mpol);
 void mpol_free_shared_policy(struct shared_policy *sp);
 struct mempolicy *mpol_shared_policy_lookup(struct shared_policy *sp,
-					    unsigned long idx);
+					    pgoff_t idx);
 
 struct mempolicy *get_task_policy(struct task_struct *p);
 struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
@@ -216,7 +210,7 @@ static inline void mpol_free_shared_policy(struct shared_policy *sp)
 }
 
 static inline struct mempolicy *
-mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
+mpol_shared_policy_lookup(struct shared_policy *sp, pgoff_t idx)
 {
 	return NULL;
 }
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 121bb490481b..065e886ec9b6 100644
--- a/mm/mempolicy.c
+++ 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)
 {
 	struct rb_node *n = sp->root.rb_node;
 
@@ -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)
 {
 	struct mempolicy *pol = NULL;
 	struct sp_node *sn;
@@ -2665,8 +2665,8 @@ static struct sp_node *sp_alloc(unsigned long start, unsigned long end,
 }
 
 /* Replace a policy range. */
-static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
-				 unsigned long end, struct sp_node *new)
+static int shared_policy_replace(struct shared_policy *sp, pgoff_t start,
+				 pgoff_t end, struct sp_node *new)
 {
 	struct sp_node *n;
 	struct sp_node *n_new = NULL;
-- 
2.35.3