proc/maps: replace proc_maps_private->pid with "struct inode *inode"

m_start() can use get_proc_task() instead, and "struct inode *"
provides more potentially useful info, see the next changes.

Signed-off-by: Oleg Nesterov <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Cyrill Gorcunov <[e-mail]>
Cc: "Eric W. Biederman" <[e-mail]>
Cc: Greg Ungerer <[e-mail]>
Cc: "Kirill A. Shutemov" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/proc/internal.h

···
  * task_[no]mmu.c
  */
 struct proc_maps_private {
-	struct pid *pid;
+	struct inode *inode;
 	struct task_struct *task;
 	struct mm_struct *mm;
 #ifdef CONFIG_MMU

fs/proc/task_mmu.c

···
 	if (last_addr == -1UL)
 		return NULL;
 
-	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
+	priv->task = get_proc_task(priv->inode);
 	if (!priv->task)
 		return ERR_PTR(-ESRCH);
 
···
 	if (!priv)
 		return -ENOMEM;
 
-	priv->pid = proc_pid(inode);
+	priv->inode = inode;
 	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
 	if (IS_ERR(priv->mm)) {
 		int err = PTR_ERR(priv->mm);

fs/proc/task_nommu.c

···
 	loff_t n = *pos;
 
 	/* pin the task and mm whilst we play with them */
-	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
+	priv->task = get_proc_task(priv->inode);
 	if (!priv->task)
 		return ERR_PTR(-ESRCH);
 
···
 	if (!priv)
 		return -ENOMEM;
 
-	priv->pid = proc_pid(inode);
+	priv->inode = inode;
 	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
 	if (IS_ERR(priv->mm)) {
 		int err = PTR_ERR(priv->mm);