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Commit 42584c81 authored by Yoshihiro YUNOMAE's avatar Yoshihiro YUNOMAE Committed by Steven Rostedt
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tracing: Have saved_cmdlines use the seq_read infrastructure 

Current tracing_saved_cmdlines_read() implementation is naive; It allocates
a large buffer, constructs output data to that buffer for each read
operation, and then copies a portion of the buffer to the user space
buffer. This has several issues such as slow memory allocation, high
CPU usage, and even corruption of the output data.

The seq_read infrastructure is made to handle this type of work.
By converting it to use seq_read() the code becomes smaller, simplified,
as well as correct.

Link: http://lkml.kernel.org/p/20140220084431.3839.51793.stgit@yunodevel



Signed-off-by: default avatarHidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarYoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 81dc9f0e

kernel/trace/trace.c

+54 −35
Original line number Diff line number Diff line
@@ -3699,55 +3699,74 @@ static const struct file_operations tracing_readme_fops = { 
	.llseek		= generic_file_llseek,

};



static ssize_t

tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,

				size_t cnt, loff_t *ppos)

static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)

{

	char *buf_comm;

	char *file_buf;

	char *buf;

	int len = 0;

	int pid;

	int i;

	unsigned int *ptr = v;



	file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);

	if (!file_buf)

		return -ENOMEM;

	if (*pos || m->count)

		ptr++;



	buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);

	if (!buf_comm) {

		kfree(file_buf);

		return -ENOMEM;

	(*pos)++;



	for (; ptr < &map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) {

		if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)

			continue;



		return ptr;

	}



	buf = file_buf;

	return NULL;

}



	for (i = 0; i < SAVED_CMDLINES; i++) {

		int r;

static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)

{

	void *v;

	loff_t l = 0;



		pid = map_cmdline_to_pid[i];

		if (pid == -1 || pid == NO_CMDLINE_MAP)

			continue;

	v = &map_cmdline_to_pid[0];

	while (l <= *pos) {

		v = saved_cmdlines_next(m, v, &l);

		if (!v)

			return NULL;

	}



		trace_find_cmdline(pid, buf_comm);

		r = sprintf(buf, "%d %s\n", pid, buf_comm);

		buf += r;

		len += r;

	return v;

}



	len = simple_read_from_buffer(ubuf, cnt, ppos,

				      file_buf, len);

static void saved_cmdlines_stop(struct seq_file *m, void *v)

{

}



	kfree(file_buf);

	kfree(buf_comm);

static int saved_cmdlines_show(struct seq_file *m, void *v)

{

	char buf[TASK_COMM_LEN];

	unsigned int *pid = v;



	return len;

	trace_find_cmdline(*pid, buf);

	seq_printf(m, "%d %s\n", *pid, buf);

	return 0;

}



static const struct seq_operations tracing_saved_cmdlines_seq_ops = {

	.start		= saved_cmdlines_start,

	.next		= saved_cmdlines_next,

	.stop		= saved_cmdlines_stop,

	.show		= saved_cmdlines_show,

};



static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)

{

	if (tracing_disabled)

		return -ENODEV;



	return seq_open(filp, &tracing_saved_cmdlines_seq_ops);

}



static const struct file_operations tracing_saved_cmdlines_fops = {

    .open       = tracing_open_generic,

    .read       = tracing_saved_cmdlines_read,

    .llseek	= generic_file_llseek,

	.open		= tracing_saved_cmdlines_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= seq_release,

};



static ssize_t