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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c232d8248a0909af2b525f001a1eb70432d20f3d..82ced406aacf810b9fd45818ef943b35d3b003b8 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -400,6 +400,26 @@ 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
@@ -2361,46 +2381,32 @@ 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;
                }
 
@@ -2426,7 +2432,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
                iter->tr->waiter = NULL;
 
                if (signal_pending(current)) {
-                       read = -EINTR;
+                       sret = -EINTR;
                        goto out;
                }
 
@@ -2496,6 +2502,7 @@ 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);
@@ -2526,24 +2533,16 @@ 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 ee53d706066f4c063a0a4d45e9ee9aeb00967191..8845033ab49db7c98889854256c032a2702f38aa 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -155,6 +155,7 @@ struct tracer {
 struct trace_seq {
        unsigned char           buffer[PAGE_SIZE];
        unsigned int            len;
+       unsigned int            readpos;
 };
 
 /*
@@ -301,6 +302,8 @@ extern int trace_selftest_startup_sched_switch(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;