[PATCH] slub: avoid false-postive warning

[Arnd Bergmann]

The slub allocator gives us some incorrect warnings when
CONFIG_PROFILE_ANNOTATED_BRANCHES is set, as the unlikely()
macro prevents it from seeing that the return code matches
what it was before:

mm/slub.c: In function âkmem_cache_free_bulkâ:
mm/slub.c:262:23: error: âdf.sâ may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2943:3: error: âdf.cntâ may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2933:4470: error: âdf.freelistâ may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2943:3: error: âdf.tailâ may be used uninitialized in this function [-Werror=maybe-uninitialized]

I have not been able to come up with a perfect way for dealing with
this, the three options I see are:

- add a bogus initialization, which would increase the runtime overhead
- replace unlikely() with unlikely_notrace()
- remove the unlikely() annotation completely

I checked the object code for a typical x86 configuration and the
last two cases produce the same result, so I went for the last
one, which is the simplest.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 2b3e740609e9..68b84f93d38d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3076,7 +3076,7 @@ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
 		struct detached_freelist df;
 
 		size = build_detached_freelist(s, size, p, &df);
-		if (unlikely(!df.page))
+		if (!df.page)
 			continue;
 
 		slab_free(df.s, df.page, df.freelist, df.tail, df.cnt,_RET_IP_);
-- 
2.9.0