+ mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: replace (20 - PAGE_SHIFT) with common macros for pages<->MB conversion
has been added to the -mm mm-new branch.  Its filename is
     mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
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fixup patches in mm-new.

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------------------------------------------------------
From: Ye Liu <liuye@kylinos.cn>
Subject: mm: replace (20 - PAGE_SHIFT) with common macros for pages<->MB conversion
Date: Fri, 18 Jul 2025 10:41:32 +0800

Replace repeated (20 - PAGE_SHIFT) calculations with standard macros:
- MB_TO_PAGES(mb)    converts MB to page count
- PAGES_TO_MB(pages) converts pages to MB

No functional change.

Link: https://lkml.kernel.org/r/20250718024134.1304745-1-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lai jiangshan <jiangshanlai@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h    |    9 +++++++++
 kernel/rcu/rcuscale.c |    2 +-
 kernel/sched/fair.c   |    5 ++---
 mm/backing-dev.c      |    2 +-
 mm/huge_memory.c      |    2 +-
 mm/swap.c             |    2 +-
 6 files changed, 15 insertions(+), 7 deletions(-)

--- a/include/linux/mm.h~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/include/linux/mm.h
@@ -69,6 +69,15 @@ static inline void totalram_pages_add(lo
 
 extern void * high_memory;
 
+/*
+ * Convert between pages and MB
+ * 20 is the shift for 1MB (2^20 = 1MB)
+ * PAGE_SHIFT is the shift for page size (e.g., 12 for 4KB pages)
+ * So (20 - PAGE_SHIFT) converts between pages and MB
+ */
+#define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
+#define MB_TO_PAGES(mb)    ((mb) << (20 - PAGE_SHIFT))
+
 #ifdef CONFIG_SYSCTL
 extern int sysctl_legacy_va_layout;
 #else
--- a/kernel/rcu/rcuscale.c~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/kernel/rcu/rcuscale.c
@@ -796,7 +796,7 @@ kfree_scale_thread(void *arg)
 		pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
 		       (unsigned long long)(end_time - start_time), kfree_loops,
 		       rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
-		       (mem_begin - mem_during) >> (20 - PAGE_SHIFT));
+		       PAGES_TO_MB(mem_begin - mem_during));
 
 		if (shutdown) {
 			smp_mb(); /* Assign before wake. */
--- a/kernel/sched/fair.c~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/kernel/sched/fair.c
@@ -1512,7 +1512,7 @@ static unsigned int task_nr_scan_windows
 	 * by the PTE scanner and NUMA hinting faults should be trapped based
 	 * on resident pages
 	 */
-	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
+	nr_scan_pages = MB_TO_PAGES(sysctl_numa_balancing_scan_size);
 	rss = get_mm_rss(p->mm);
 	if (!rss)
 		rss = nr_scan_pages;
@@ -1949,8 +1949,7 @@ bool should_numa_migrate_memory(struct t
 		}
 
 		def_th = sysctl_numa_balancing_hot_threshold;
-		rate_limit = sysctl_numa_balancing_promote_rate_limit << \
-			(20 - PAGE_SHIFT);
+		rate_limit = MB_TO_PAGES(sysctl_numa_balancing_promote_rate_limit);
 		numa_promotion_adjust_threshold(pgdat, rate_limit, def_th);
 
 		th = pgdat->nbp_threshold ? : def_th;
--- a/mm/backing-dev.c~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/mm/backing-dev.c
@@ -510,7 +510,7 @@ static void wb_update_bandwidth_workfn(s
 /*
  * Initial write bandwidth: 100 MB/s
  */
-#define INIT_BW		(100 << (20 - PAGE_SHIFT))
+#define INIT_BW		MB_TO_PAGES(100)
 
 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
 		   gfp_t gfp)
--- a/mm/huge_memory.c~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/mm/huge_memory.c
@@ -911,7 +911,7 @@ static int __init hugepage_init(void)
 	 * where the extra memory used could hurt more than TLB overhead
 	 * is likely to save.  The admin can still enable it through /sys.
 	 */
-	if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
+	if (totalram_pages() < MB_TO_PAGES(512)) {
 		transparent_hugepage_flags = 0;
 		return 0;
 	}
--- a/mm/swap.c~mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion
+++ a/mm/swap.c
@@ -1096,7 +1096,7 @@ static const struct ctl_table swap_sysct
  */
 void __init swap_setup(void)
 {
-	unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
+	unsigned long megs = PAGES_TO_MB(totalram_pages());
 
 	/* Use a smaller cluster for small-memory machines */
 	if (megs < 16)
_

Patches currently in -mm which might be from liuye@kylinos.cn are

mm-replace-20-page_shift-with-common-macros-for-pages-mb-conversion.patch