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Date:   Tue, 3 Oct 2023 02:21:34 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>
cc:     Andi Kleen <ak@linux.intel.com>, Christoph Lameter <cl@linux.com>,
        Matthew Wilcox <willy@infradead.org>,
        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>,
        "Huang, Ying" <ying.huang@intel.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: [PATCH v2 06/12] mempolicy trivia: use pgoff_t in shared mempolicy
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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@google.com>
---
 include/linux/mempolicy.h | 20 +++++++-------------
 mm/mempolicy.c            | 12 ++++++------
 2 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 325b7200c311..c69f9480d5e4 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -107,22 +107,16 @@ 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;
-	struct mempolicy *policy;
-};
-
 struct shared_policy {
 	struct rb_root root;
 	rwlock_t lock;
 };
+struct sp_node {
+	struct rb_node nd;
+	pgoff_t start, end;
+	struct mempolicy *policy;
+};
 
 int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst);
 void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol);
@@ -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 c7906a034959..1d3f9e1ecbb8 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2448,8 +2448,8 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
  * lookup first element intersecting start-end.  Caller holds sp->lock for
  * reading or for writing
  */
-static struct sp_node *
-sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
+static struct sp_node *sp_lookup(struct shared_policy *sp,
+					pgoff_t start, pgoff_t end)
 {
 	struct rb_node *n = sp->root.rb_node;
 
@@ -2503,8 +2503,8 @@ 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)
+struct mempolicy *mpol_shared_policy_lookup(struct shared_policy *sp,
+						pgoff_t idx)
 {
 	struct mempolicy *pol = NULL;
 	struct sp_node *sn;
@@ -2672,8 +2672,8 @@ 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