linux-kernel - [PATCH 2/2] mm/memremap: Remove unused get_dev

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Message-ID: <20250902051421.162498-2-apopple@nvidia.com>
Date: Tue,  2 Sep 2025 15:14:21 +1000
From: Alistair Popple <apopple@...dia.com>
To: linux-mm@...ck.org,
	akpm@...ux-foundation.org
Cc: david@...hat.com,
	osalvador@...e.de,
	jgg@...pe.ca,
	jhubbard@...dia.com,
	peterx@...hat.com,
	linux-kernel@...r.kernel.org,
	dan.j.williams@...el.com,
	Alistair Popple <apopple@...dia.com>
Subject: [PATCH 2/2] mm/memremap: Remove unused get_dev_pagemap() parameter

GUP no longer uses get_dev_pagemap(). As it was the only user of the
get_dev_pagemap() pgmap caching feature it can be removed.

Signed-off-by: Alistair Popple <apopple@...dia.com>
---
 include/linux/memremap.h |  6 ++----
 mm/memory_hotplug.c      |  2 +-
 mm/memremap.c            | 22 ++++------------------
 3 files changed, 7 insertions(+), 23 deletions(-)

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 4aa151914eabb..5cfc2ae6c98bd 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -204,8 +204,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid);
 void memunmap_pages(struct dev_pagemap *pgmap);
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
 void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap);
-struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
-		struct dev_pagemap *pgmap);
+struct dev_pagemap *get_dev_pagemap(unsigned long pfn);
 bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
 
 unsigned long memremap_compat_align(void);
@@ -227,8 +226,7 @@ static inline void devm_memunmap_pages(struct device *dev,
 {
 }
 
-static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
-		struct dev_pagemap *pgmap)
+static inline struct dev_pagemap *get_dev_pagemap(unsigned long pfn)
 {
 	return NULL;
 }
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1f15af712bc34..14e98c89f5b4d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -375,7 +375,7 @@ struct page *pfn_to_online_page(unsigned long pfn)
 	 * the section may be 'offline' but 'valid'. Only
 	 * get_dev_pagemap() can determine sub-section online status.
 	 */
-	pgmap = get_dev_pagemap(pfn, NULL);
+	pgmap = get_dev_pagemap(pfn);
 	put_dev_pagemap(pgmap);
 
 	/* The presence of a pgmap indicates ZONE_DEVICE offline pfn */
diff --git a/mm/memremap.c b/mm/memremap.c
index b0ce0d8254bd8..3b4717cf3a6b2 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -153,14 +153,14 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
 				"altmap not supported for multiple ranges\n"))
 		return -EINVAL;
 
-	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->start), NULL);
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->start));
 	if (conflict_pgmap) {
 		WARN(1, "Conflicting mapping in same section\n");
 		put_dev_pagemap(conflict_pgmap);
 		return -ENOMEM;
 	}
 
-	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->end), NULL);
+	conflict_pgmap = get_dev_pagemap(PHYS_PFN(range->end));
 	if (conflict_pgmap) {
 		WARN(1, "Conflicting mapping in same section\n");
 		put_dev_pagemap(conflict_pgmap);
@@ -394,26 +394,12 @@ EXPORT_SYMBOL_GPL(devm_memunmap_pages);
 /**
  * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
  * @pfn: page frame number to lookup page_map
- * @pgmap: optional known pgmap that already has a reference
- *
- * If @pgmap is non-NULL and covers @pfn it will be returned as-is.  If @pgmap
- * is non-NULL but does not cover @pfn the reference to it will be released.
  */
-struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
-		struct dev_pagemap *pgmap)
+struct dev_pagemap *get_dev_pagemap(unsigned long pfn)
 {
+	struct dev_pagemap *pgmap;
 	resource_size_t phys = PFN_PHYS(pfn);
 
-	/*
-	 * In the cached case we're already holding a live reference.
-	 */
-	if (pgmap) {
-		if (phys >= pgmap->range.start && phys <= pgmap->range.end)
-			return pgmap;
-		put_dev_pagemap(pgmap);
-	}
-
-	/* fall back to slow path lookup */
 	rcu_read_lock();
 	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
 	if (pgmap && !percpu_ref_tryget_live_rcu(&pgmap->ref))
-- 
2.47.2