linux-kernel - [PATCH 2/2] mm/mmzone.h: simplify is_highmem

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Date:   Fri, 23 Apr 2021 23:38:11 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jonathan Corbet <corbet@....net>, Mike Rapoport <rppt@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 2/2] mm/mmzone.h: simplify is_highmem_idx()

From: Mike Rapoport <rppt@...ux.ibm.com>

There is a lot of historical ifdefery in is_highmem_idx() and its helper
zone_movable_is_highmem() that was required because of two different paths
for nodes and zones initialization that were selected at compile time.

Until commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP
option") the movable_zone variable was only available for configurations
that had CONFIG_HAVE_MEMBLOCK_NODE_MAP enabled so the test in
zone_movable_is_highmem() used that variable only for such configurations.
For other configurations the test checked if the index of ZONE_MOVABLE was
greater by 1 than the index of ZONE_HIGMEM and then movable zone was
considered a highmem zone. Needless to say, ZONE_MOVABLE - 1 equals
ZONE_HIGMEM by definition when CONFIG_HIGHMEM=y.

Commit 3f08a302f533 ("mm: remove CONFIG_HAVE_MEMBLOCK_NODE_MAP option")
made movable_zone variable always available. Since this variable is set to
ZONE_HIGHMEM if CONFIG_HIGHMEM is enabled and highmem zone is populated, it
is enough to check whether

	zone_idx == ZONE_MOVABLE && movable_zone == ZONE_HIGMEM

to test if zone index points to a highmem zone.

Remove zone_movable_is_highmem() that is not used anywhere except
is_highmem_idx() and use the test above in is_highmem_idx() instead.

Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
 include/linux/mmzone.h | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3b2205741048..6a1ac643b65e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -968,22 +968,11 @@ static inline void zone_set_nid(struct zone *zone, int nid) {}

 extern int movable_zone;

-#ifdef CONFIG_HIGHMEM
-static inline int zone_movable_is_highmem(void)
-{
-#ifdef CONFIG_NEED_MULTIPLE_NODES
-	return movable_zone == ZONE_HIGHMEM;
-#else
-	return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
-#endif
-}
-#endif
-
 static inline int is_highmem_idx(enum zone_type idx)
 {
 #ifdef CONFIG_HIGHMEM
 	return (idx == ZONE_HIGHMEM ||
-		(idx == ZONE_MOVABLE && zone_movable_is_highmem()));
+		(idx == ZONE_MOVABLE && movable_zone == ZONE_HIGHMEM));
 #else
 	return 0;
 #endif
-- 
2.29.2