latencytop: change /proc task_struct access method

Change getting task_struct by get_proc_task() at read or write time,
and returns -ESRCH if get_proc_task() returns NULL.
This is same behavior as other /proc files.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 28 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 85e06e498078..91a1bd67ac1d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -314,9 +314,12 @@ static int proc_pid_schedstat(struct task_struct *task, char *buffer)
 static int lstats_show_proc(struct seq_file *m, void *v)
 {
         int i;
-        struct task_struct *task = m->private;
-        seq_puts(m, "Latency Top version : v0.1\n");
+        struct inode *inode = m->private;
+        struct task_struct *task = get_proc_task(inode);
 
+        if (!task)
+                return -ESRCH;
+        seq_puts(m, "Latency Top version : v0.1\n");
         for (i = 0; i < 32; i++) {
                 if (task->latency_record[i].backtrace[0]) {
                         int q;
@@ -341,43 +344,24 @@ static int lstats_show_proc(struct seq_file *m, void *v)
                 }
 
         }
+        put_task_struct(task);
         return 0;
 }
 
 static int lstats_open(struct inode *inode, struct file *file)
 {
-        int ret;
-        struct seq_file *m;
-        struct task_struct *task = get_proc_task(inode);
-
-        if (!task)
-                return -ENOENT;
-        ret = single_open(file, lstats_show_proc, NULL);
-        if (!ret) {
-                m = file->private_data;
-                m->private = task;
-        }
-        return ret;
-}
-
-static int lstats_release(struct inode *inode, struct file *file)
-{
-        struct seq_file *m = file->private_data;
-        struct task_struct *task = m->private;
-
-        put_task_struct(task);
-        return single_release(inode, file);
+        return single_open(file, lstats_show_proc, inode);
 }
 
 static ssize_t lstats_write(struct file *file, const char __user *buf,
                             size_t count, loff_t *offs)
 {
-        struct seq_file *m;
-        struct task_struct *task;
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
 
-        m = file->private_data;
-        task = m->private;
+        if (!task)
+                return -ESRCH;
         clear_all_latency_tracing(task);
+        put_task_struct(task);
 
         return count;
 }
@@ -387,7 +371,7 @@ static const struct file_operations proc_lstats_operations = {
         .read           = seq_read,
         .write          = lstats_write,
         .llseek         = seq_lseek,
-        .release        = lstats_release,
+        .release        = single_release,
 };
 
 #endif