[PATCH] task_vsize() locking cleanup

task_vsize() doesn't need mm->mmap_sem for the CONFIG_MMU case; the
semaphore doesn't prevent mm->total_vm from going stale or getting
inconsistent with other numbers regardless.  Also, KSTK_EIP() and
KSTK_ESP() don't want or need protection from mm->mmap_sem either.  So this
pushes mm->mmap_sem to task_vsize() in the CONFIG_MMU=n task_vsize().

Also, hoist the prototype of task_vsize() into proc_fs.h

The net result of this is a small speedup of procps for CONFIG_MMU.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/proc/array.c

@@ -299,7 +299,6 @@ int proc_pid_status(struct task_struct *task, char * buffer)
 	return buffer - orig;
 }
 
-extern unsigned long task_vsize(struct mm_struct *);
 int proc_pid_stat(struct task_struct *task, char * buffer)
 {
 	unsigned long vsize, eip, esp, wchan;
@@ -318,11 +317,9 @@ int proc_pid_stat(struct task_struct *task, char * buffer)
 	vsize = eip = esp = 0;
 	mm = get_task_mm(task);
 	if (mm) {
-		down_read(&mm->mmap_sem);
 		vsize = task_vsize(mm);
 		eip = KSTK_EIP(task);
 		esp = KSTK_ESP(task);
-		up_read(&mm->mmap_sem);
 	}
 
 	get_task_comm(tcomm, task);

fs/proc/task_nommu.c

@@ -68,11 +68,12 @@ unsigned long task_vsize(struct mm_struct *mm)
 	struct mm_tblock_struct *tbp;
 	unsigned long vsize = 0;
 
+	down_read(&mm->mmap_sem);
 	for (tbp = &mm->context.tblock; tbp; tbp = tbp->next) {
 		if (tbp->rblock)
 			vsize += kobjsize(tbp->rblock->kblock);
 	}
-
+	up_read(&mm->mmap_sem);
 	return vsize;
 }
 

include/linux/proc_fs.h

@@ -86,10 +86,13 @@ extern struct proc_dir_entry *proc_root_kcore;
 extern void proc_root_init(void);
 extern void proc_misc_init(void);
 
+struct mm_struct;
+
 struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *);
 struct dentry *proc_pid_unhash(struct task_struct *p);
 void proc_pid_flush(struct dentry *proc_dentry);
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir);
+unsigned long task_vsize(struct mm_struct *);
 
 extern struct proc_dir_entry *create_proc_entry(const char *name, mode_t mode,
 						struct proc_dir_entry *parent);