xfs: use %px for data pointers when debugging

Starting with commit 57e734423ad ("vsprintf: refactor %pK code out of
pointer"), the behavior of the raw '%p' printk format specifier was
changed to print a 32-bit hash of the pointer value to avoid leaking
kernel pointers into dmesg.  For most situations that's good.

This is /undesirable/ behavior when we're trying to debug XFS, however,
so define a PTR_FMT that prints the actual pointer when we're in debug
mode.

Note that %p for tracepoints still prints the raw pointer, so in the
long run we could consider rewriting some of these messages as
tracepoints.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 74d3576c8043..bee51a14a906 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -291,4 +291,16 @@ static inline uint64_t howmany_64(uint64_t x, uint32_t y)
 #define XFS_IS_REALTIME_MOUNT(mp) (0)
 #endif
 
+/*
+ * Starting in Linux 4.15, the %p (raw pointer value) printk modifier
+ * prints a hashed version of the pointer to avoid leaking kernel
+ * pointers into dmesg.  If we're trying to debug the kernel we want the
+ * raw values, so override this behavior as best we can.
+ */
+#ifdef DEBUG
+# define PTR_FMT "%px"
+#else
+# define PTR_FMT "%p"
+#endif
+
 #endif /* __XFS_LINUX__ */