Commit 3c56819b authored by Eduard - Gabriel Munteanu's avatar Eduard - Gabriel Munteanu Committed by Steven Rostedt
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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
......@@ -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,
};
......
......@@ -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);
......
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