cifs: Add tracepoints for errors on flush or fsync

Makes it easier to debug errors on writeback that happen later,
and are being returned on flush or fsync

For example:
  writetest-17829 [002] .... 13583.407859: cifs_flush_err: ino=90 rc=-28
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/file.c

@@ -2632,8 +2632,10 @@ int cifs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(file);
 
 	rc = file_write_and_wait_range(file, start, end);
-	if (rc)
+	if (rc) {
+		trace_cifs_fsync_err(file_inode(file)->i_ino, rc);
 		return rc;
+	}
 
 	xid = get_xid();
 
@@ -2666,7 +2668,8 @@ int cifs_flush(struct file *file, fl_owner_t id)
 		rc = filemap_write_and_wait(inode->i_mapping);
 
 	cifs_dbg(FYI, "Flush inode %p file %p rc %d\n", inode, file, rc);
-
+	if (rc)
+		trace_cifs_flush_err(inode->i_ino, rc);
 	return rc;
 }
 

fs/cifs/trace.h

@@ -547,6 +547,33 @@ DEFINE_EVENT(smb3_exit_err_class, smb3_##name,    \
 
 DEFINE_SMB3_EXIT_ERR_EVENT(exit_err);
 
+
+DECLARE_EVENT_CLASS(smb3_sync_err_class,
+	TP_PROTO(unsigned long ino,
+		int	rc),
+	TP_ARGS(ino, rc),
+	TP_STRUCT__entry(
+		__field(unsigned long, ino)
+		__field(int, rc)
+	),
+	TP_fast_assign(
+		__entry->ino = ino;
+		__entry->rc = rc;
+	),
+	TP_printk("\tino=%lu rc=%d",
+		__entry->ino, __entry->rc)
+)
+
+#define DEFINE_SMB3_SYNC_ERR_EVENT(name)          \
+DEFINE_EVENT(smb3_sync_err_class, cifs_##name,    \
+	TP_PROTO(unsigned long ino,		\
+		int	rc),			\
+	TP_ARGS(ino, rc))
+
+DEFINE_SMB3_SYNC_ERR_EVENT(fsync_err);
+DEFINE_SMB3_SYNC_ERR_EVENT(flush_err);
+
+
 DECLARE_EVENT_CLASS(smb3_enter_exit_class,
 	TP_PROTO(unsigned int xid,
 		const char *func_name),