From: Li Zefan <lizf@cn.fujitsu.com>
Date: Mon, 1 Jun 2009 07:35:46 +0000 (+0800)
Subject: tracing/events: introduce __dynamic_array()
X-Git-Tag: v2.6.31-rc1~401^2~11^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7fcb7c472f455d1711eb5a7633204dba8800a6d6;p=pandora-kernel.git

tracing/events: introduce __dynamic_array()

__string() is limited:

  - it's a char array, but we may want to define array with other types
  - a source string should be available, but we may just know the string size

We introduce __dynamic_array() to break those limitations, and __string()
becomes a wrapper of it. As a side effect, now __get_str() can be used
in TP_fast_assign but not only TP_print.

Take XFS for example, we have the string length in the dirent, but the
string itself is not NULL-terminated, so __dynamic_array() can be used:

TRACE_EVENT(xfs_dir2,
	TP_PROTO(struct xfs_da_args *args),
	TP_ARGS(args),

	TP_STRUCT__entry(
		__field(int, namelen)
		__dynamic_array(char, name, args->namelen + 1)
		...
	),

	TP_fast_assign(
		char *name = __get_str(name);

		if (args->namelen)
			memcpy(name, args->name, args->namelen);
		name[args->namelen] = '\0';

		__entry->namelen = args->namelen;
	),

	TP_printk("name %.*s namelen %d",
		  __entry->namelen ? __get_str(name) : NULL
		  __entry->namelen)
);

[ Impact: allow defining dynamic size arrays ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2384D2.3080403@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

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