From: Chad Goodman <chad.goodman@gmail.com>
Date: Wed, 19 Dec 2012 07:18:41 +0000 (-0800)
Subject: IOSCHED: prevent aliased requests from starving other I/O
X-Git-Url: https://ziggy471.com/git/gitweb.cgi?p=ziggy471-sgn2-jb.git;a=commitdiff;h=318f9ee41a74bcf5d07dfbcac883cd9a50bdc072

IOSCHED: prevent aliased requests from starving other I/O

Signed-off-by: Ziggy <ziggy@ziggy471.com>
---

--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1502,16 +1502,11 @@ static void cfq_add_rq_rb(struct request
 {
 	struct cfq_queue *cfqq = RQ_CFQQ(rq);
 	struct cfq_data *cfqd = cfqq->cfqd;
-	struct request *__alias, *prev;
+	struct request *prev;
 
 	cfqq->queued[rq_is_sync(rq)]++;
 
-	/*
-	 * looks a little odd, but the first insert might return an alias.
-	 * if that happens, put the alias on the dispatch list
-	 */
-	while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
-		cfq_dispatch_insert(cfqd->queue, __alias);
+	elv_rb_add(&cfqq->sort_list, rq);
 
 	if (!cfq_cfqq_on_rr(cfqq))
 		cfq_add_cfqq_rr(cfqd, cfqq);
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -77,10 +77,8 @@ static void
 deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
 {
 	struct rb_root *root = deadline_rb_root(dd, rq);
-	struct request *__alias;
 
-	while (unlikely(__alias = elv_rb_add(root, rq)))
-		deadline_move_request(dd, __alias);
+	elv_rb_add(root, rq);
 }
 
 static inline void
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -353,7 +353,7 @@ static struct request *elv_rqhash_find(s
  * RB-tree support functions for inserting/lookup/removal of requests
  * in a sorted RB tree.
  */
-struct request *elv_rb_add(struct rb_root *root, struct request *rq)
+void elv_rb_add(struct rb_root *root, struct request *rq)
 {
 	struct rb_node **p = &root->rb_node;
 	struct rb_node *parent = NULL;
@@ -365,15 +365,12 @@ struct request *elv_rb_add(struct rb_roo
 
 		if (blk_rq_pos(rq) < blk_rq_pos(__rq))
 			p = &(*p)->rb_left;
-		else if (blk_rq_pos(rq) > blk_rq_pos(__rq))
+		else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
 			p = &(*p)->rb_right;
-		else
-			return __rq;
 	}
 
 	rb_link_node(&rq->rb_node, parent, p);
 	rb_insert_color(&rq->rb_node, root);
-	return NULL;
 }
 EXPORT_SYMBOL(elv_rb_add);
 
--- a/block/vr-iosched.c
+++ b/block/vr-iosched.c
@@ -73,14 +73,7 @@ return q->elevator->elevator_data;
 static void
 vr_add_rq_rb(struct vr_data *vd, struct request *rq)
 {
-struct request *alias = elv_rb_add(&vd->sort_list, rq);
-
-if (unlikely(alias)) {
-vr_move_request(vd, alias);
-alias = elv_rb_add(&vd->sort_list, rq);
-BUG_ON(alias);
-}
-
+elv_rb_add(&vd->sort_list, rq);
 if (blk_rq_pos(rq) >= vd->last_sector) {
 if (!vd->next_rq || blk_rq_pos(vd->next_rq) > blk_rq_pos(rq))
 vd->next_rq = rq;
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -146,7 +146,7 @@ extern struct request *elv_rb_latter_req
 /*
  * rb support functions.
  */
-extern struct request *elv_rb_add(struct rb_root *, struct request *);
+extern void elv_rb_add(struct rb_root *, struct request *);
 extern void elv_rb_del(struct rb_root *, struct request *);
 extern struct request *elv_rb_find(struct rb_root *, sector_t);