[PATCH 5.4 285/344] btrfs: separate definition of assertion failure handlers

Greg Kroah-Hartman
2020-02-21T08:31:55Z

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