linux-kernel - [PATCH 1/2] mm/cma: drop incorrect alignment check in cma_init_reserved

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Date: Thu,  4 Apr 2024 16:25:14 +0000
From: Frank van der Linden <fvdl@...gle.com>
To: linux-mm@...ck.org, muchun.song@...ux.dev, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, Frank van der Linden <fvdl@...gle.com>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, David Hildenbrand <david@...hat.com>
Subject: [PATCH 1/2] mm/cma: drop incorrect alignment check in cma_init_reserved_mem

cma_init_reserved_mem uses IS_ALIGNED to check if the size
represented by one bit in the cma allocation bitmask is
aligned with CMA_MIN_ALIGNMENT_BYTES (pageblock size).

However, this is too strict, as this will fail if
order_per_bit > pageblock_order, which is a valid configuration.

We could check IS_ALIGNED both ways, but since both numbers are
powers of two, no check is needed at all.

Signed-off-by: Frank van der Linden <fvdl@...gle.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: David Hildenbrand <david@...hat.com>
Fixes: de9e14eebf33 ("drivers: dma-contiguous: add initialization from device tree")
---
 mm/cma.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 01f5a8f71ddf..3e9724716bad 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -182,10 +182,6 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 	if (!size || !memblock_is_region_reserved(base, size))
 		return -EINVAL;
 
-	/* alignment should be aligned with order_per_bit */
-	if (!IS_ALIGNED(CMA_MIN_ALIGNMENT_PAGES, 1 << order_per_bit))
-		return -EINVAL;
-
 	/* ensure minimal alignment required by mm core */
 	if (!IS_ALIGNED(base | size, CMA_MIN_ALIGNMENT_BYTES))
 		return -EINVAL;
-- 
2.44.0.478.gd926399ef9-goog