[PATCH] remove preempt_disable from pdflush

It seems by the comments the statements were only there to prevent the
thread from finding itself as TASK_RUNNING after a kernel preemption.
Since we reverted to the original preemption behavior (which does not do
that) it should be safe.  Looking over the code confirms - it seems to
not be doing anything evil and is properly locked otherwise.

mm/pdflush.c

@@ -78,12 +78,6 @@ struct pdflush_work {
 	unsigned long when_i_went_to_sleep;
 };
 
-/*
- * preemption is disabled in pdflush.  There was a bug in preempt
- * which was causing pdflush to get flipped into state TASK_RUNNING
- * when it performed a spin_unlock.  That bug is probably fixed,
- * but play it safe.  The preempt-off paths are very short.
- */
 static int __pdflush(struct pdflush_work *my_work)
 {
 	daemonize();
@@ -100,7 +94,6 @@ static int __pdflush(struct pdflush_work *my_work)
 	my_work->fn = NULL;
 	my_work->who = current;
 
-	preempt_disable();
 	spin_lock_irq(&pdflush_lock);
 	nr_pdflush_threads++;
 //	printk("pdflush %d [%d] starts\n", nr_pdflush_threads, current->pid);
@@ -114,9 +107,7 @@ static int __pdflush(struct pdflush_work *my_work)
 
 		schedule();
 
-		preempt_enable();
 		(*my_work->fn)(my_work->arg0);
-		preempt_disable();
 
 		/*
 		 * Thread creation: For how long have there been zero
@@ -150,7 +141,6 @@ static int __pdflush(struct pdflush_work *my_work)
 	nr_pdflush_threads--;
 //	printk("pdflush %d [%d] ends\n", nr_pdflush_threads, current->pid);
 	spin_unlock_irq(&pdflush_lock);
-	preempt_enable();
 	return 0;
 }