+ cma-split-resrvation-of-fixed-area-into-a-helper-function.patch added to mm-new branch

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

The patch titled
     Subject: cma: split reservation of fixed area into a helper function
has been added to the -mm mm-new branch.  Its filename is
     cma-split-resrvation-of-fixed-area-into-a-helper-function.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/cma-split-resrvation-of-fixed-area-into-a-helper-function.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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------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: cma: split reservation of fixed area into a helper function
Date: Wed, 2 Jul 2025 20:36:04 +0300

Move the check that verifies that reservation of fixed area does not cross
HIGHMEM boundary and the actual memblock_resrve() call into a helper
function.

This makes code more readable and decouples logic related to
CONFIG_HIGHMEM from the core functionality of
__cma_declare_contiguous_nid().

Link: https://lkml.kernel.org/r/20250702173605.2198924-3-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/cma.c |   41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

--- a/mm/cma.c~cma-split-resrvation-of-fixed-area-into-a-helper-function
+++ a/mm/cma.c
@@ -353,6 +353,30 @@ static void __init list_insert_sorted(
 	}
 }
 
+static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
+{
+	if (IS_ENABLED(CONFIG_HIGHMEM)) {
+		phys_addr_t highmem_start = __pa(high_memory - 1) + 1;
+
+		/*
+		 * If allocating at a fixed base the request region must not
+		 * cross the low/high memory boundary.
+		 */
+		if (base < highmem_start && base + size > highmem_start) {
+			pr_err("Region at %pa defined on low/high memory boundary (%pa)\n",
+			       &base, &highmem_start);
+			return -EINVAL;
+		}
+	}
+
+	if (memblock_is_region_reserved(base, size) ||
+	    memblock_reserve(base, size) < 0) {
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
 static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 			phys_addr_t size, phys_addr_t limit,
 			phys_addr_t alignment, unsigned int order_per_bit,
@@ -408,15 +432,6 @@ static int __init __cma_declare_contiguo
 	if (!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit))
 		return -EINVAL;
 
-	/*
-	 * If allocating at a fixed base the request region must not cross the
-	 * low/high memory boundary.
-	 */
-	if (fixed && base < highmem_start && base + size > highmem_start) {
-		pr_err("Region at %pa defined on low/high memory boundary (%pa)\n",
-			&base, &highmem_start);
-		return -EINVAL;
-	}
 
 	/*
 	 * If the limit is unspecified or above the memblock end, its effective
@@ -434,10 +449,10 @@ static int __init __cma_declare_contiguo
 
 	/* Reserve memory */
 	if (fixed) {
-		if (memblock_is_region_reserved(base, size) ||
-		    memblock_reserve(base, size) < 0) {
-			return -EBUSY;
-		}
+		int err = cma_fixed_reserve(base, size);
+
+		if (err)
+			return err;
 	} else {
 		phys_addr_t addr = 0;
 
_

Patches currently in -mm which might be from rppt@kernel.org are

cma-move-__cma_declare_contiguous_nid-before-its-usage.patch
cma-split-resrvation-of-fixed-area-into-a-helper-function.patch
cma-move-allocation-from-highmem-to-a-helper-function.patch