xfs: xfs_iomap_prealloc_size() tracepoint

Add a tracepoint to provide some feedback on preallocation size
calculation.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_iomap.c

@@ -518,6 +518,9 @@ check_writeio:
 	if (alloc_blocks < mp->m_writeio_blocks)
 		alloc_blocks = mp->m_writeio_blocks;
 
+	trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
+				      mp->m_writeio_blocks);
+
 	return alloc_blocks;
 }
 

fs/xfs/xfs_trace.h

@@ -619,6 +619,30 @@ DECLARE_EVENT_CLASS(xfs_iref_class,
 		  (char *)__entry->caller_ip)
 )
 
+TRACE_EVENT(xfs_iomap_prealloc_size,
+	TP_PROTO(struct xfs_inode *ip, xfs_fsblock_t blocks, int shift,
+		 unsigned int writeio_blocks),
+	TP_ARGS(ip, blocks, shift, writeio_blocks),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_ino_t, ino)
+		__field(xfs_fsblock_t, blocks)
+		__field(int, shift)
+		__field(unsigned int, writeio_blocks)
+	),
+	TP_fast_assign(
+		__entry->dev = VFS_I(ip)->i_sb->s_dev;
+		__entry->ino = ip->i_ino;
+		__entry->blocks = blocks;
+		__entry->shift = shift;
+		__entry->writeio_blocks = writeio_blocks;
+	),
+	TP_printk("dev %d:%d ino 0x%llx prealloc blocks %llu shift %d "
+		  "m_writeio_blocks %u",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->ino,
+		  __entry->blocks, __entry->shift, __entry->writeio_blocks)
+)
+
 #define DEFINE_IREF_EVENT(name) \
 DEFINE_EVENT(xfs_iref_class, name, \
 	TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip), \