linux-kernel - [PATCH 2/3] cma: split resrvation of fixed area into a helper function

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Message-ID: <20250702173605.2198924-3-rppt@kernel.org>
Date: Wed,  2 Jul 2025 20:36:04 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexandre Ghiti <alexghiti@...osinc.com>,
	David Hildenbrand <david@...hat.com>,
	Mike Rapoport <rppt@...nel.org>,
	Oscar Salvador <osalvador@...e.de>,
	Pratyush Yadav <ptyadav@...zon.de>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 2/3] cma: split resrvation of fixed area into a helper function

From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>

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().

Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
 mm/cma.c | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 9bf95f8f0f33..1df8ff312d99 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -352,6 +352,30 @@ 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,
@@ -407,15 +431,6 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 	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
@@ -433,10 +448,10 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 
 	/* 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;
 
-- 
2.47.2