linux-kernel - [PATCH] mm: swap: make free_swap_and_cache()/swapcache

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Date:   Wed, 23 Aug 2017 15:31:42 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Jérôme Glisse <jglisse@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Huang Ying <ying.huang@...el.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] mm: swap: make free_swap_and_cache()/swapcache_prepare() inline functions

We get a build warning from a boolean expression that is never used:

mm/madvise.c: In function 'madvise_free_pte_range':
include/linux/swap.h:490:55: error: value computed is not used [-Werror=unused-value]
 #define free_swap_and_cache(e) (is_migration_entry(e) || is_device_private_entry(e))
                                                       ^~
mm/madvise.c:353:4: note: in expansion of macro 'free_swap_and_cache'
    free_swap_and_cache(entry);

This changes the two macros to a compound expression that gcc does
not warn about. Changing them to inline functions would have been
nicer but is not possible here because that would introduce a recursive
header file dependency.

Fixes: mmotm ("mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 include/linux/swap.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 2be396acdf48..8a807292037f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -487,8 +487,8 @@ static inline void show_swap_cache_info(void)
 {
 }
 
-#define free_swap_and_cache(e) (is_migration_entry(e) || is_device_private_entry(e))
-#define swapcache_prepare(e) (is_migration_entry(e) || is_device_private_entry(e))
+#define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
+#define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 
 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 {
-- 
2.9.0