linux-kernel - [PATCH 02/10] um: Fix MAX_ORDER usage in linux

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Date:   Wed, 15 Mar 2023 14:31:25 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>
Subject: [PATCH 02/10] um: Fix MAX_ORDER usage in linux_main()

MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
can deliver is MAX_ORDER-1.

Fix MAX_ORDER usage in linux_main().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Richard Weinberger <richard@....at>
Cc: Anton Ivanov <anton.ivanov@...bridgegreys.com>
Cc: Johannes Berg <johannes@...solutions.net>
---
 arch/um/kernel/um_arch.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 8dcda617b8bf..5e5a9c8e0e5d 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -368,10 +368,10 @@ int __init linux_main(int argc, char **argv)
 	max_physmem = TASK_SIZE - uml_physmem - iomem_size - MIN_VMALLOC;
 
 	/*
-	 * Zones have to begin on a 1 << MAX_ORDER page boundary,
+	 * Zones have to begin on a 1 << MAX_ORDER-1 page boundary,
 	 * so this makes sure that's true for highmem
 	 */
-	max_physmem &= ~((1 << (PAGE_SHIFT + MAX_ORDER)) - 1);
+	max_physmem &= ~((1 << (PAGE_SHIFT + MAX_ORDER - 1)) - 1);
 	if (physmem_size + iomem_size > max_physmem) {
 		highmem = physmem_size + iomem_size - max_physmem;
 		physmem_size -= highmem;
-- 
2.39.2