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Subject[PATCH 1/5] ftrace: add readpos to struct trace_seq; add trace_seq_to_user()
From c69153a56ddcdc09a2135a4d9cbf95ab4bdd08a0 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@iki.fi>
Date: Sat, 26 Apr 2008 21:58:39 +0300
Subject: [PATCH] ftrace: add readpos to struct trace_seq; add trace_seq_to_user()

Refactor code from tracing_read_pipe() and create trace_seq_to_user().
Moved trace_seq_reset() call before iter->trace->read() call so that
when all leftover data is returned, trace_seq is reset automatically.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
---

Steven,

do you approve this?


kernel/trace/trace.c | 73 ++++++++++++++++++++++++-------------------------
kernel/trace/trace.h | 3 ++
2 files changed, 39 insertions(+), 37 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 04366ae..06c85b3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -403,6 +403,26 @@ static void
trace_seq_reset(struct trace_seq *s)
{
s->len = 0;
+ s->readpos = 0;
+}
+
+ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
+{
+ int len;
+ int ret;
+
+ if (s->len <= s->readpos)
+ return -EBUSY;
+
+ len = s->len - s->readpos;
+ if (cnt > len)
+ cnt = len;
+ ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
+ if (ret)
+ return -EFAULT;
+
+ s->readpos += len;
+ return cnt;
}

static void
@@ -2406,46 +2426,32 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
struct trace_iterator *iter = filp->private_data;
struct trace_array_cpu *data;
static cpumask_t mask;
- static int start;
unsigned long flags;
#ifdef CONFIG_FTRACE
int ftrace_save;
#endif
- int read = 0;
int cpu;
- int len;
- int ret;
+ ssize_t sret;

/* return any leftover data */
- if (iter->seq.len > start) {
- len = iter->seq.len - start;
- if (cnt > len)
- cnt = len;
- ret = copy_to_user(ubuf, iter->seq.buffer + start, cnt);
- if (ret)
- cnt = -EFAULT;
-
- start += len;
+ sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+ if (sret != -EBUSY)
+ return sret;
+ sret = 0;

- return cnt;
- }
+ trace_seq_reset(&iter->seq);

mutex_lock(&trace_types_lock);
if (iter->trace->read) {
- ret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
- if (ret) {
- read = ret;
+ sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
+ if (sret)
goto out;
- }
}

- trace_seq_reset(&iter->seq);
- start = 0;
-
while (trace_empty(iter)) {

if ((filp->f_flags & O_NONBLOCK)) {
- read = -EAGAIN;
+ sret = -EAGAIN;
goto out;
}

@@ -2471,7 +2477,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
iter->tr->waiter = NULL;

if (signal_pending(current)) {
- read = -EINTR;
+ sret = -EINTR;
goto out;
}

@@ -2541,6 +2547,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
}

while (find_next_entry_inc(iter) != NULL) {
+ int ret;
int len = iter->seq.len;

ret = print_trace_line(iter);
@@ -2571,24 +2578,16 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
local_irq_restore(flags);

/* Now copy what we have to the user */
- read = iter->seq.len;
- if (read > cnt)
- read = cnt;
-
- ret = copy_to_user(ubuf, iter->seq.buffer, read);
-
- if (read < iter->seq.len)
- start = read;
- else
+ sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+ if (iter->seq.readpos >= iter->seq.len)
trace_seq_reset(&iter->seq);
-
- if (ret)
- read = -EFAULT;
+ if (sret == -EBUSY)
+ sret = 0;

out:
mutex_unlock(&trace_types_lock);

- return read;
+ return sret;
}

static ssize_t
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index a151c87..3e15c23 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -160,6 +160,7 @@ struct tracer {
struct trace_seq {
unsigned char buffer[PAGE_SIZE];
unsigned int len;
+ unsigned int readpos;
};

/*
@@ -303,6 +304,8 @@ extern int trace_selftest_startup_sysprof(struct tracer *trace,

extern void *head_page(struct trace_array_cpu *data);
extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...);
+extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,
+ size_t cnt);
extern long ns2usecs(cycle_t nsec);

extern unsigned long trace_flags;
--
1.5.3.7


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