xfs: more info from kmem deadlocks and high-level error msgs

In an effort to get more useful out of "possible memory
allocation deadlock" messages, print the size of the
requested allocation, and dump the stack if the xfs error
level is tuned high.

The stack dump is implemented in define_xfs_printk_level()
for error levels >= LOGLEVEL_ERR, partly because it
seems generically useful, and also because kmem.c has
no knowledge of xfs error level tunables or other such bits,
it's very kmem-specific.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/kmem.c

@@ -55,9 +55,9 @@ kmem_alloc(size_t size, xfs_km_flags_t flags)
 			return ptr;
 		if (!(++retries % 100))
 			xfs_err(NULL,
-		"%s(%u) possible memory allocation deadlock in %s (mode:0x%x)",
+	"%s(%u) possible memory allocation deadlock size %u in %s (mode:0x%x)",
 				current->comm, current->pid,
-				__func__, lflags);
+				(unsigned int)size, __func__, lflags);
 		congestion_wait(BLK_RW_ASYNC, HZ/50);
 	} while (1);
 }

fs/xfs/xfs_message.c

@@ -17,6 +17,7 @@
 
 #include "xfs.h"
 #include "xfs_fs.h"
+#include "xfs_error.h"
 #include "xfs_format.h"
 #include "xfs_log_format.h"
 #include "xfs_trans_resv.h"
@@ -43,6 +44,7 @@ void func(const struct xfs_mount *mp, const char *fmt, ...)	\
 {								\
 	struct va_format	vaf;				\
 	va_list			args;				\
+	int			level;				\
 								\
 	va_start(args, fmt);					\
 								\
@@ -51,6 +53,11 @@ void func(const struct xfs_mount *mp, const char *fmt, ...)	\
 								\
 	__xfs_printk(kern_level, mp, &vaf);			\
 	va_end(args);						\
+								\
+	if (!kstrtoint(kern_level, 0, &level) &&		\
+	    level <= LOGLEVEL_ERR &&				\
+	    xfs_error_level >= XFS_ERRLEVEL_HIGH)		\
+		xfs_stack_trace();				\
 }								\
 
 define_xfs_printk_level(xfs_emerg, KERN_EMERG);