Commit 3c56819b authored by Eduard - Gabriel Munteanu's avatar Eduard - Gabriel Munteanu Committed by Steven Rostedt
Browse files

tracing: splice support for tracing_pipe 



Added and implemented tracing_pipe_fops->splice_read(). This allows
userspace programs to get tracing data more efficiently.

Signed-off-by: default avatarEduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent b91facc3

kernel/trace/trace.c

+136 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/fs.h>

#include <linux/kprobes.h>

#include <linux/writeback.h>

#include <linux/splice.h>



#include <linux/stacktrace.h>

#include <linux/ring_buffer.h>
@@ -364,6 +365,25 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt) 
	return cnt;

}



ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)

{

	int len;

	void *ret;



	if (s->len <= s->readpos)

		return -EBUSY;



	len = s->len - s->readpos;

	if (cnt > len)

		cnt = len;

	ret = memcpy(buf, s->buffer + s->readpos, cnt);

	if (!ret)

		return -EFAULT;



	s->readpos += len;

	return cnt;

}



static void

trace_print_seq(struct seq_file *m, struct trace_seq *s)

{
@@ -2493,6 +2513,121 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 
	return sret;

}



static void tracing_pipe_buf_release(struct pipe_inode_info *pipe,

				     struct pipe_buffer *buf)

{

	__free_page(buf->page);

}



static void tracing_spd_release_pipe(struct splice_pipe_desc *spd,

				     unsigned int idx)

{

	__free_page(spd->pages[idx]);

}



static struct pipe_buf_operations tracing_pipe_buf_ops = {

	.can_merge = 0,

	.map = generic_pipe_buf_map,

	.unmap = generic_pipe_buf_unmap,

	.confirm = generic_pipe_buf_confirm,

	.release = tracing_pipe_buf_release,

	.steal = generic_pipe_buf_steal,

	.get = generic_pipe_buf_get,

};



static ssize_t tracing_splice_read_pipe(struct file *filp,

					loff_t *ppos,

					struct pipe_inode_info *pipe,

					size_t len,

					unsigned int flags)

{

	struct page *pages[PIPE_BUFFERS];

	struct partial_page partial[PIPE_BUFFERS];

	struct trace_iterator *iter = filp->private_data;

	struct splice_pipe_desc spd = {

		.pages = pages,

		.partial = partial,

		.nr_pages = 0, /* This gets updated below. */

		.flags = flags,

		.ops = &tracing_pipe_buf_ops,

		.spd_release = tracing_spd_release_pipe,

	};

	ssize_t ret;

	size_t count, rem;

	unsigned int i;



	mutex_lock(&trace_types_lock);



	if (iter->trace->splice_read) {

		ret = iter->trace->splice_read(iter, filp,

					       ppos, pipe, len, flags);

		if (ret)

			goto out;

	}



	ret = tracing_wait_pipe(filp);

	if (ret <= 0)

		goto out;



	if (!iter->ent && !find_next_entry_inc(iter)) {

		ret = -EFAULT;

		goto out;

	}



	/* Fill as many pages as possible. */

	for (i = 0, rem = len; i < PIPE_BUFFERS && rem; i++) {

		pages[i] = alloc_page(GFP_KERNEL);



		/* Seq buffer is page-sized, exactly what we need. */

		for (;;) {

			count = iter->seq.len;

			ret = print_trace_line(iter);

			count = iter->seq.len - count;

			if (rem < count) {

				rem = 0;

				iter->seq.len -= count;

				break;

			}

			if (ret == TRACE_TYPE_PARTIAL_LINE) {

				iter->seq.len -= count;

				break;

			}



			trace_consume(iter);

			rem -= count;

			if (!find_next_entry_inc(iter))	{

				rem = 0;

				iter->ent = NULL;

				break;

			}

		}



		/* Copy the data into the page, so we can start over. */

		ret = trace_seq_to_buffer(&iter->seq,

					  page_address(pages[i]),

					  iter->seq.len);

		if (ret < 0) {

			__free_page(pages[i]);

			break;

		}

		partial[i].offset = 0;

		partial[i].len = iter->seq.len;



		trace_seq_reset(&iter->seq);

	}



	mutex_unlock(&trace_types_lock);



	spd.nr_pages = i;



	return splice_to_pipe(pipe, &spd);



out:

	mutex_unlock(&trace_types_lock);



	return ret;

}



static ssize_t

tracing_entries_read(struct file *filp, char __user *ubuf,

		     size_t cnt, loff_t *ppos)
@@ -2656,6 +2791,7 @@ static struct file_operations tracing_pipe_fops = { 
	.open		= tracing_open_pipe,

	.poll		= tracing_poll_pipe,

	.read		= tracing_read_pipe,

	.splice_read	= tracing_splice_read_pipe,

	.release	= tracing_release_pipe,

};

kernel/trace/trace.h

+6 −0
Original line number Diff line number Diff line
@@ -353,6 +353,12 @@ struct tracer { 
	ssize_t			(*read)(struct trace_iterator *iter,

					struct file *filp, char __user *ubuf,

					size_t cnt, loff_t *ppos);

	ssize_t			(*splice_read)(struct trace_iterator *iter,

					       struct file *filp,

					       loff_t *ppos,

					       struct pipe_inode_info *pipe,

					       size_t len,

					       unsigned int flags);

#ifdef CONFIG_FTRACE_STARTUP_TEST

	int			(*selftest)(struct tracer *trace,

					    struct trace_array *tr);