On Fri, Oct 05, 2018 at 03:19:34PM -0700, Andrew Morton wrote:

On Fri,  5 Oct 2018 00:07:04 +0300 Mike Rapoport [off-list ref] wrote:

quoted

When a memblock allocation APIs are called with align = 0, the alignment is
implicitly set to SMP_CACHE_BYTES.

Replace all such uses of memblock APIs with the 'align' parameter explicitly
set to SMP_CACHE_BYTES and stop implicit alignment assignment in the
memblock internal allocation functions.

For the case when memblock APIs are used via helper functions, e.g. like
iommu_arena_new_node() in Alpha, the helper functions were detected with
Coccinelle's help and then manually examined and updated where appropriate.

...

--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -1298,9 +1298,6 @@ static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 {
 	phys_addr_t found;
 
-	if (!align)
-		align = SMP_CACHE_BYTES;
-

Can we add a WARN_ON_ONCE(!align) here?  To catch unconverted code
which sneaks in later on.

Here it goes:

From baec825c58e8bc11371433d3a4b20b2216877a50 Mon Sep 17 00:00:00 2001

From: Mike Rapoport <redacted>
Date: Mon, 8 Oct 2018 11:22:10 +0300
Subject: [PATCH] memblock: warn if zero alignment was requested

After update of all memblock users to explicitly specify SMP_CACHE_BYTES
alignment rather than use 0, it is still possible that uncovered users
may sneak in. Add a WARN_ON_ONCE for such cases.

Signed-off-by: Mike Rapoport <redacted>
---
 mm/memblock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memblock.c b/mm/memblock.c
index 0bbae56..5fefc70 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -1298,6 +1298,9 @@ static phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
 {
 	phys_addr_t found;
 
+	if (WARN_ON_ONCE(!align))
+		align = SMP_CACHE_BYTES;
+
 	found = memblock_find_in_range_node(size, align, start, end, nid,
 					    flags);
 	if (found && !memblock_reserve(found, size)) {

@@ -1420,6 +1423,9 @@ static void * __init memblock_alloc_internal(
 	if (WARN_ON_ONCE(slab_is_available()))
 		return kzalloc_node(size, GFP_NOWAIT, nid);
 
+	if (WARN_ON_ONCE(!align))
+		align = SMP_CACHE_BYTES;
+
 	if (max_addr > memblock.current_limit)
 		max_addr = memblock.current_limit;
 again:

-- 
2.7.4


-- 
Sincerely yours,
Mike.