xfs: uncached buffer tracing needs to print bno

Useless:

xfs_buf_get_uncached: dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_unlock:       dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_submit:       dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_hold:         dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_iowait:       dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_iodone:       dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_iowait_done:  dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_rele:         dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...

Useful:


xfs_buf_get_uncached: dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_unlock:       dev 253:32 bno 0xffffffffffffffff nblks 0x1 ...
xfs_buf_submit:       dev 253:32 bno 0x200b5 nblks 0x1 ...
xfs_buf_hold:         dev 253:32 bno 0x200b5 nblks 0x1 ...
xfs_buf_iowait:       dev 253:32 bno 0x200b5 nblks 0x1 ...
xfs_buf_iodone:       dev 253:32 bno 0x200b5 nblks 0x1 ...
xfs_buf_iowait_done:  dev 253:32 bno 0x200b5 nblks 0x1 ...
xfs_buf_rele:         dev 253:32 bno 0x200b5 nblks 0x1 ...

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

fs/xfs/xfs_trace.h

@@ -280,7 +280,10 @@ DECLARE_EVENT_CLASS(xfs_buf_class,
 	),
 	TP_fast_assign(
 		__entry->dev = bp->b_target->bt_dev;
-		__entry->bno = bp->b_bn;
+		if (bp->b_bn == XFS_BUF_DADDR_NULL)
+			__entry->bno = bp->b_maps[0].bm_bn;
+		else
+			__entry->bno = bp->b_bn;
 		__entry->nblks = bp->b_length;
 		__entry->hold = atomic_read(&bp->b_hold);
 		__entry->pincount = atomic_read(&bp->b_pin_count);