xfs: introduce CONFIG_XFS_WARN

Running a CONFIG_XFS_DEBUG kernel in production environments is not
the best idea as it introduces significant overhead, can change
the behaviour of algorithms (such as allocation) to improve test
coverage, and (most importantly) panic the machine on non-fatal
errors.

There are many cases where all we want to do is run a
kernel with more bounds checking enabled, such as is provided by the
ASSERT() statements throughout the code, but without all the
potential overhead and drawbacks.

This patch converts all the ASSERT statements to evaluate as
WARN_ON(1) statements and hence if they fail dump a warning and a
stack trace to the log. This has minimal overhead and does not
change any algorithms, and will allow us to find strange "out of
bounds" problems more easily on production machines.

There are a few places where assert statements contain debug only
code. These are converted to be debug-or-warn only code so that we
still get all the assert checks in the code.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 14e59d953b7..800f896a6cc 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -293,22 +293,34 @@ static inline __uint64_t howmany_64(__uint64_t x, __uint32_t y)
 #define ASSERT_ALWAYS(expr)	\
 	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
 
-#ifndef DEBUG
-#define ASSERT(expr)	((void)0)
+#ifdef DEBUG
+#define ASSERT(expr)	\
+	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
 
 #ifndef STATIC
-# define STATIC static noinline
+# define STATIC noinline
 #endif
 
-#else /* DEBUG */
+#else	/* !DEBUG */
+
+#ifdef XFS_WARN
 
 #define ASSERT(expr)	\
-	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
+	(unlikely(expr) ? (void)0 : asswarn(#expr, __FILE__, __LINE__))
 
 #ifndef STATIC
-# define STATIC noinline
+# define STATIC static noinline
+#endif
+
+#else	/* !DEBUG && !XFS_WARN */
+
+#define ASSERT(expr)	((void)0)
+
+#ifndef STATIC
+# define STATIC static noinline
 #endif
 
+#endif /* XFS_WARN */
 #endif /* DEBUG */
 
 #endif /* __XFS_LINUX__ */