releases/5.4.22/btrfs-separate-definition-of-assertion-failure-handl.patch

From 4f6676e07edee820c963eb5c457af16c219abd46 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Mon, 16 Dec 2019 20:00:48 +0100
Subject: btrfs: separate definition of assertion failure handlers

From: David Sterba <dsterba@suse.com>

[ Upstream commit 68c467cbb2f389b6c933e235bce0d1756fc8cc34 ]

There's a report where objtool detects unreachable instructions, eg.:

  fs/btrfs/ctree.o: warning: objtool: btrfs_search_slot()+0x2d4: unreachable instruction

This seems to be a false positive due to compiler version. The cause is
in the ASSERT macro implementation that does the conditional check as
IS_DEFINED(CONFIG_BTRFS_ASSERT) and not an #ifdef.

To avoid that, use the ifdefs directly.

There are still 2 reports that aren't fixed:

  fs/btrfs/extent_io.o: warning: objtool: __set_extent_bit()+0x71f: unreachable instruction
  fs/btrfs/relocation.o: warning: objtool: find_data_references()+0x4e0: unreachable instruction

Co-developed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/ctree.h | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 290ca193c6c0f..169075550a5a2 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3107,17 +3107,21 @@ do {								\
 	rcu_read_unlock();					\
 } while (0)
 
-__cold
-static inline void assfail(const char *expr, const char *file, int line)
+#ifdef CONFIG_BTRFS_ASSERT
+__cold __noreturn
+static inline void assertfail(const char *expr, const char *file, int line)
 {
-	if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) {
-		pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
-		BUG();
-	}
+	pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
+	BUG();
 }
 
-#define ASSERT(expr)	\
-	(likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
+#define ASSERT(expr)						\
+	(likely(expr) ? (void)0 : assertfail(#expr, __FILE__, __LINE__))
+
+#else
+static inline void assertfail(const char *expr, const char* file, int line) { }
+#define ASSERT(expr)	(void)(expr)
+#endif
 
 /*
  * Use that for functions that are conditionally exported for sanity tests but
-- 
2.20.1