[PATCH] btrfs: do not evaluate the expression with !CONFIG_BTRFS_ASSERT

[Josef Bacik <josef@toxicpanda.com>]

While investigating a performance issue I noticed that turning off
CONFIG_BTRFS_ASSERT had no effect in what I was seeing in perf,
specifically check_setget_bounds() was around 5% for this workload.
Upon investigation I realized that I made a mistake when I added
ASSERT(), I would still evaluate the expression, but simply ignore the
result.

This is useless, and has a marked impact on performance.  This
microbenchmark is the watered down version of an application that is
experiencing performance issues, and does renames and creates over and
over again.  Doing these operations 200k times without this patch takes
13 seconds on my machine.  With this patch it takes 7 seconds.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h        | 2 +-
 fs/btrfs/struct-funcs.c | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 9c7e466f27a9..b0fe8cca7e86 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3238,7 +3238,7 @@ static inline void assertfail(const char *expr, const char *file, int line)
 
 #else
 static inline void assertfail(const char *expr, const char* file, int line) { }
-#define ASSERT(expr)	(void)(expr)
+#define ASSERT(expr)	((void)0)
 #endif
 
 /*
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c
index 079b059818e9..f44dc1207792 100644
--- a/fs/btrfs/struct-funcs.c
+++ b/fs/btrfs/struct-funcs.c
@@ -17,6 +17,7 @@ static inline void put_unaligned_le8(u8 val, void *p)
        *(u8 *)p = val;
 }
 
+#ifdef CONFIG_BTRFS_ASSERT
 static bool check_setget_bounds(const struct extent_buffer *eb,
 				const void *ptr, unsigned off, int size)
 {
@@ -37,6 +38,7 @@ static bool check_setget_bounds(const struct extent_buffer *eb,
 
 	return true;
 }
+#endif
 
 /*
  * Macro templates that define helpers to read/write extent buffer data of a
-- 
2.24.1