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 <[e-mail]>
Reviewed-by: Brian Foster <[e-mail]>
Signed-off-by: Ben Myers <[e-mail]>

fs/xfs/Kconfig

···
 
 	  If unsure, say N.
 
+config XFS_WARN
+	bool "XFS Verbose Warnings"
+	depends on XFS_FS && !XFS_DEBUG
+	help
+	  Say Y here to get an XFS build with many additional warnings.
+	  It converts ASSERT checks to WARN, so will log any out-of-bounds
+	  conditions that occur that would otherwise be missed. It is much
+	  lighter weight than XFS_DEBUG and does not modify algorithms and will
+	  not cause the kernel to panic on non-fatal errors.
+
+	  However, similar to XFS_DEBUG, it is only advisable to use this if you
+	  are debugging a particular problem.
+
 config XFS_DEBUG
 	bool "XFS Debugging support"
 	depends on XFS_FS

fs/xfs/mrlock.h

···
 
 typedef struct {
 	struct rw_semaphore	mr_lock;
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	int			mr_writer;
 #endif
 } mrlock_t;
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 #define mrinit(mrp, name)	\
 	do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
 #else
···
 static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
 {
 	down_write_nested(&mrp->mr_lock, subclass);
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	mrp->mr_writer = 1;
 #endif
 }
···
 {
 	if (!down_write_trylock(&mrp->mr_lock))
 		return 0;
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	mrp->mr_writer = 1;
 #endif
 	return 1;
···
 
 static inline void mrunlock_excl(mrlock_t *mrp)
 {
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	mrp->mr_writer = 0;
 #endif
 	up_write(&mrp->mr_lock);
···
 
 static inline void mrdemote(mrlock_t *mrp)
 {
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	mrp->mr_writer = 0;
 #endif
 	downgrade_write(&mrp->mr_lock);

fs/xfs/xfs.h

···
 #define XFS_BUF_LOCK_TRACKING 1
 #endif
 
+#ifdef CONFIG_XFS_WARN
+#define XFS_WARN 1
+#endif
+
+
 #include "xfs_linux.h"
 
 #endif	/* __XFS_H__ */

fs/xfs/xfs_alloc_btree.c

···
 };
 
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 STATIC int
 xfs_allocbt_keys_inorder(
 	struct xfs_btree_cur	*cur,
···
 	.init_ptr_from_cur	= xfs_allocbt_init_ptr_from_cur,
 	.key_diff		= xfs_allocbt_key_diff,
 	.buf_ops		= &xfs_allocbt_buf_ops,
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	.keys_inorder		= xfs_allocbt_keys_inorder,
 	.recs_inorder		= xfs_allocbt_recs_inorder,
 #endif

fs/xfs/xfs_bmap_btree.c

···
 };
 
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 STATIC int
 xfs_bmbt_keys_inorder(
 	struct xfs_btree_cur	*cur,
···
 	.init_ptr_from_cur	= xfs_bmbt_init_ptr_from_cur,
 	.key_diff		= xfs_bmbt_key_diff,
 	.buf_ops		= &xfs_bmbt_buf_ops,
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	.keys_inorder		= xfs_bmbt_keys_inorder,
 	.recs_inorder		= xfs_bmbt_recs_inorder,
 #endif

fs/xfs/xfs_btree.h

···
 
 	const struct xfs_buf_ops	*buf_ops;
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	/* check that k1 is lower than k2 */
 	int	(*keys_inorder)(struct xfs_btree_cur *cur,
 				union xfs_btree_key *k1,

fs/xfs/xfs_dir2_node.c

···
 	xfs_dir2_leaf_t		*leaf1;		/* first leaf structure */
 	xfs_dir2_leaf_t		*leaf2;		/* second leaf structure */
 	int			mid;		/* midpoint leaf index */
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	int			oldstale;	/* old count of stale leaves */
 #endif
 	int			oldsum;		/* old total leaf count */
···
 	ents2 = xfs_dir3_leaf_ents_p(leaf2);
 
 	oldsum = hdr1.count + hdr2.count;
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	oldstale = hdr1.stale + hdr2.stale;
 #endif
 	mid = oldsum >> 1;

fs/xfs/xfs_ialloc_btree.c

···
 	.verify_write = xfs_inobt_write_verify,
 };
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 STATIC int
 xfs_inobt_keys_inorder(
 	struct xfs_btree_cur	*cur,
···
 	.init_ptr_from_cur	= xfs_inobt_init_ptr_from_cur,
 	.key_diff		= xfs_inobt_key_diff,
 	.buf_ops		= &xfs_inobt_buf_ops,
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	.keys_inorder		= xfs_inobt_keys_inorder,
 	.recs_inorder		= xfs_inobt_recs_inorder,
 #endif

fs/xfs/xfs_inode.c

···
 	trace_xfs_ilock_demote(ip, lock_flags, _RET_IP_);
 }
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 int
 xfs_isilocked(
 	xfs_inode_t		*ip,

fs/xfs/xfs_linux.h

···
 #define ASSERT_ALWAYS(expr)	\
 	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
 
-#ifndef DEBUG
-#define ASSERT(expr)	((void)0)
-
-#ifndef STATIC
-# define STATIC static noinline
-#endif
-
-#else /* DEBUG */
-
+#ifdef DEBUG
 #define ASSERT(expr)	\
 	(unlikely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))
 
···
 # define STATIC noinline
 #endif
 
+#else	/* !DEBUG */
+
+#ifdef XFS_WARN
+
+#define ASSERT(expr)	\
+	(unlikely(expr) ? (void)0 : asswarn(#expr, __FILE__, __LINE__))
+
+#ifndef STATIC
+# 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__ */

fs/xfs/xfs_message.c

···
 }
 
 void
+asswarn(char *expr, char *file, int line)
+{
+	xfs_warn(NULL, "Assertion failed: %s, file: %s, line: %d",
+		expr, file, line);
+	WARN_ON(1);
+}
+
+void
 assfail(char *expr, char *file, int line)
 {
 	xfs_emerg(NULL, "Assertion failed: %s, file: %s, line: %d",

fs/xfs/xfs_message.h

···
 	xfs_printk_ratelimited(xfs_debug, dev, fmt, ##__VA_ARGS__)
 
 extern void assfail(char *expr, char *f, int l);
+extern void asswarn(char *expr, char *f, int l);
 
 extern void xfs_hex_dump(void *p, int length);
 

fs/xfs/xfs_trans.h

···
 	int64_t			t_res_fdblocks_delta; /* on-disk only chg */
 	int64_t			t_frextents_delta;/* superblock freextents chg*/
 	int64_t			t_res_frextents_delta; /* on-disk only chg */
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 	int64_t			t_ag_freeblks_delta; /* debugging counter */
 	int64_t			t_ag_flist_delta; /* debugging counter */
 	int64_t			t_ag_btree_delta; /* debugging counter */
···
 #define	xfs_trans_get_block_res(tp)	((tp)->t_blk_res)
 #define	xfs_trans_set_sync(tp)		((tp)->t_flags |= XFS_TRANS_SYNC)
 
-#ifdef DEBUG
+#if defined(DEBUG) || defined(XFS_WARN)
 #define	xfs_trans_agblocks_delta(tp, d)	((tp)->t_ag_freeblks_delta += (int64_t)d)
 #define	xfs_trans_agflist_delta(tp, d)	((tp)->t_ag_flist_delta += (int64_t)d)
 #define	xfs_trans_agbtree_delta(tp, d)	((tp)->t_ag_btree_delta += (int64_t)d)