[PATCH 1/2] alloc_tag: avoid current->alloc_tag manipulations when profiling is disabled

[Suren Baghdasaryan <surenb@google.com>]

When memory allocation profiling is disabled there is no need to update
current->alloc_tag and these manipulations add unnecessary overhead. Fix
the overhead by skipping these extra updates.

Fixes: b951aaff5035 ("mm: enable page allocation tagging")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: stable@vger.kernel.org
---
 include/linux/alloc_tag.h | 11 ++++++++---
 lib/alloc_tag.c           |  2 ++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index 0bbbe537c5f9..a946e0203e6d 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -224,9 +224,14 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
 
 #define alloc_hooks_tag(_tag, _do_alloc)				\
 ({									\
-	struct alloc_tag * __maybe_unused _old = alloc_tag_save(_tag);	\
-	typeof(_do_alloc) _res = _do_alloc;				\
-	alloc_tag_restore(_tag, _old);					\
+	typeof(_do_alloc) _res;						\
+	if (mem_alloc_profiling_enabled()) {				\
+		struct alloc_tag * __maybe_unused _old;			\
+		_old = alloc_tag_save(_tag);				\
+		_res = _do_alloc;					\
+		alloc_tag_restore(_tag, _old);				\
+	} else								\
+		_res = _do_alloc;					\
 	_res;								\
 })
 
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 7dcebf118a3e..4c373f444eb1 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -29,6 +29,8 @@ EXPORT_SYMBOL(_shared_alloc_tag);
 
 DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
 			mem_alloc_profiling_key);
+EXPORT_SYMBOL(mem_alloc_profiling_key);
+
 DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed);
 
 struct alloc_tag_kernel_section kernel_tags = { NULL, 0 };

base-commit: 431614f1580a03c1a653340c55ea76bd12a9403f
-- 
2.47.1.613.gc27f4b7a9f-goog