[PATCH] btrfs: relocation: fix unused variable

[Anders Roxell <anders.roxell@linaro.org>]

When CONFIG_BRTFS_ASSERT isn't enabled, variable root_objectid isn't used.

fs/btrfs/relocation.c: In function ‘insert_dirty_subv’:
fs/btrfs/relocation.c:2138:6: warning: unused variable ‘root_objectid’ [-Wunused-variable]
  u64 root_objectid = root->root_key.objectid;
      ^~~~~~~~~~~~~

Reworked by adding a runtime check in the assfail function instead of
the '#ifdef CONFIG_BTRFS_ASSERT #else ...", so the compiler sees the
condition being passed into an inline function after preprocessing.

Fixes: 7b837199c581 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots()")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 fs/btrfs/ctree.h | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index de23a7ea396d..ad7d079f2cae 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3521,21 +3521,18 @@ do {								\
 	rcu_read_unlock();					\
 } while (0)
 
-#ifdef CONFIG_BTRFS_ASSERT
-
 __cold
 static inline void assfail(const char *expr, const char *file, int line)
 {
-	pr_err("assertion failed: %s, file: %s, line: %d\n",
-	       expr, file, line);
-	BUG();
+	if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) {
+		pr_err("assertion failed: %s, file: %s, line: %d\n",
+		       expr, file, line);
+		BUG();
+	}
 }
 
 #define ASSERT(expr)	\
 	(likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
-#else
-#define ASSERT(expr)	((void)0)
-#endif
 
 /*
  * Use that for functions that are conditionally exported for sanity tests but
-- 
2.19.2