[RFC v2 1/4] cma: Enforce non-zero pageblock_order during cma_init_reserved_mem()

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

cma_init_reserved_mem() checks base and size alignment with
CMA_MIN_ALIGNMENT_BYTES. However, some users might call this during
early boot when pageblock_order is 0. That means if base and size does
not have pageblock_order alignment, it can cause functional failures
during cma activate area.

So let's enforce pageblock_order to be non-zero during
cma_init_reserved_mem().

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 mm/cma.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/cma.c b/mm/cma.c
index 3e9724716bad..36d753e7a0bf 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -182,6 +182,15 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 	if (!size || !memblock_is_region_reserved(base, size))
 		return -EINVAL;
 
+	/*
+	 * CMA uses CMA_MIN_ALIGNMENT_BYTES as alignment requirement which
+	 * needs pageblock_order to be initialized. Let's enforce it.
+	 */
+	if (!pageblock_order) {
+		pr_err("pageblock_order not yet initialized. Called during early boot?\n");
+		return -EINVAL;
+	}
+
 	/* ensure minimal alignment required by mm core */
 	if (!IS_ALIGNED(base | size, CMA_MIN_ALIGNMENT_BYTES))
 		return -EINVAL;
-- 
2.46.0