ftrace: improve seq_operation of ftrace

Impact: make ftrace position computing more sane

First remove useless ->pos field. Then we needn't check seq_printf
in .show like other place.

Signed-off-by: Liming Wang <liming.wang@windriver.com>
Reviewed-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 17 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index cbf8b09f63a5..08b536a2614e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -786,7 +786,6 @@ enum {
 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
 
 struct ftrace_iterator {
-        loff_t                  pos;
         struct ftrace_page      *pg;
         unsigned                idx;
         unsigned                flags;
@@ -811,6 +810,8 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
                         iter->pg = iter->pg->next;
                         iter->idx = 0;
                         goto retry;
+                } else {
+                        iter->idx = -1;
                 }
         } else {
                 rec = &iter->pg->records[iter->idx++];
@@ -833,8 +834,6 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
         }
         spin_unlock(&ftrace_lock);
 
-        iter->pos = *pos;
-
         return rec;
 }
 
@@ -842,13 +841,15 @@ static void *t_start(struct seq_file *m, loff_t *pos)
 {
         struct ftrace_iterator *iter = m->private;
         void *p = NULL;
-        loff_t l = -1;
 
-        if (*pos > iter->pos)
-                *pos = iter->pos;
+        if (*pos > 0) {
+                if (iter->idx < 0)
+                        return p;
+                (*pos)--;
+                iter->idx--;
+        }
 
-        l = *pos;
-        p = t_next(m, p, &l);
+        p = t_next(m, p, pos);
 
         return p;
 }
@@ -859,21 +860,15 @@ static void t_stop(struct seq_file *m, void *p)
 
 static int t_show(struct seq_file *m, void *v)
 {
-        struct ftrace_iterator *iter = m->private;
         struct dyn_ftrace *rec = v;
         char str[KSYM_SYMBOL_LEN];
-        int ret = 0;
 
         if (!rec)
                 return 0;
 
         kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
 
-        ret = seq_printf(m, "%s\n", str);
-        if (ret < 0) {
-                iter->pos--;
-                iter->idx--;
-        }
+        seq_printf(m, "%s\n", str);
 
         return 0;
 }
@@ -899,7 +894,6 @@ ftrace_avail_open(struct inode *inode, struct file *file)
                 return -ENOMEM;
 
         iter->pg = ftrace_pages_start;
-        iter->pos = 0;
 
         ret = seq_open(file, &show_ftrace_seq_ops);
         if (!ret) {
@@ -986,7 +980,6 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 
         if (file->f_mode & FMODE_READ) {
                 iter->pg = ftrace_pages_start;
-                iter->pos = 0;
                 iter->flags = enable ? FTRACE_ITER_FILTER :
                         FTRACE_ITER_NOTRACE;