[PATCH] copy_process: cosmetic ->ioprio tweak

copy_process:
// holds tasklist_lock + ->siglock
       /*
        * inherit ioprio
        */
       p->ioprio = current->ioprio;

Why?  ->ioprio was already copied in dup_task_struct().  I guess this is
needed to ensure that the child can't escape
sys_ioprio_set(IOPRIO_WHO_{PGRP,USER}), yes?

In that case we don't need ->siglock held, and the comment should be
updated.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/fork.c

@@ -1150,7 +1150,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
 	/* Our parent execution domain becomes current domain
 	   These must match for thread signalling to apply */
-	   
 	p->parent_exec_id = p->self_exec_id;
 
 	/* ok, now we should be set up.. */
@@ -1173,6 +1172,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	/* Need tasklist lock for parent etc handling! */
 	write_lock_irq(&tasklist_lock);
 
+	/* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
+	p->ioprio = current->ioprio;
+
 	/*
 	 * The task hasn't been attached yet, so its cpus_allowed mask will
 	 * not be changed, nor will its assigned CPU.
@@ -1232,11 +1234,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		}
 	}
 
-	/*
-	 * inherit ioprio
-	 */
-	p->ioprio = current->ioprio;
-
 	if (likely(p->pid)) {
 		add_parent(p);
 		if (unlikely(p->ptrace & PT_PTRACED))