[PATCH] elevator insertion fixes

From: Nick Piggin <piggin@cyberone.com.au>

This fixes a bug in deadline and AS that causes insert_here to be ignored on
blk_fs_requests. This has been causing problems with SCSI requeueing code.
It makes elevator insertion more correct as advertised wrt insert_here and
REQ_SOFTBARRIER.

It also fixes a buglet in the as_requeue code where the request wasn't being
put into the front of the list (in rare cases).

diff --git a/drivers/block/as-iosched.c b/drivers/block/as-iosched.c
index e520c51d78cfeec2536de674cd429d8dc0c24a82..27384d27b5662ac0a2c4f11b2001fd6a5ec0387e 100644 (file)
--- a/drivers/block/as-iosched.c
+++ b/drivers/block/as-iosched.c
@@ -910,12 +910,7 @@ static void as_completed_request(request_queue_t *q, struct request *rq)
        struct as_rq *arq = RQ_DATA(rq);
        struct as_io_context *aic;
 
-       if (unlikely(!blk_fs_request(rq)))
-               return;
-
-       WARN_ON(blk_fs_request(rq) && arq->state == AS_RQ_NEW);
-
-       if (arq->state != AS_RQ_DISPATCHED)
+       if (unlikely(arq->state != AS_RQ_DISPATCHED))
                return;
 
        if (ad->changed_batch && ad->nr_dispatched == 1) {
@@ -1035,7 +1030,7 @@ static void as_remove_request(request_queue_t *q, struct request *rq)
 {
        struct as_rq *arq = RQ_DATA(rq);
 
-       if (unlikely(!blk_fs_request(rq)))
+       if (unlikely(arq->state == AS_RQ_NEW))
                return;
 
        if (!arq) {
@@ -1341,9 +1336,9 @@ static void as_requeue_request(request_queue_t *q, struct request *rq)
                        atomic_inc(&arq->io_context->aic->nr_dispatched);
        } else
                WARN_ON(blk_fs_request(rq)
-                               && (!(rq->flags & REQ_HARDBARRIER)) );
+                       && (!(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) );
 
-       list_add_tail(&rq->queuelist, ad->dispatch);
+       list_add(&rq->queuelist, ad->dispatch);
 
        /* Stop anticipating - let this request get through */
        as_antic_stop(ad);
@@ -1358,26 +1353,31 @@ as_insert_request(request_queue_t *q, struct request *rq,
        struct as_data *ad = q->elevator.elevator_data;
        struct as_rq *arq = RQ_DATA(rq);
 
-       if (unlikely(rq->flags & REQ_HARDBARRIER)) {
+       if (unlikely(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) {
                q->last_merge = NULL;
 
-               while (ad->next_arq[REQ_SYNC])
-                       as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
+               if (insert_here != ad->dispatch) {
+                       while (ad->next_arq[REQ_SYNC])
+                               as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
+
+                       while (ad->next_arq[REQ_ASYNC])
+                               as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
+               }
 
-               while (ad->next_arq[REQ_ASYNC])
-                       as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
+               if (!insert_here)
+                       insert_here = ad->dispatch->prev;
        }
 
        if (unlikely(!blk_fs_request(rq))) {
                if (!insert_here)
-                       insert_here = ad->dispatch->prev;
+                       insert_here = ad->dispatch;
+       }
 
+       if (insert_here) {
                list_add(&rq->queuelist, insert_here);
 
                /* Stop anticipating - let this request get through */
-               if (!list_empty(ad->dispatch)
-                       && (ad->antic_status == ANTIC_WAIT_REQ
-                               || ad->antic_status == ANTIC_WAIT_NEXT))
+               if (list_empty(ad->dispatch))
                        as_antic_stop(ad);
 
                return;

diff --git a/drivers/block/deadline-iosched.c b/drivers/block/deadline-iosched.c
index 66b11e3822e9dd898fb7c0135946d769d4105d2c..dc2b121a9239f15447d4b80b0a996f805c035657 100644 (file)
--- a/drivers/block/deadline-iosched.c
+++ b/drivers/block/deadline-iosched.c
@@ -627,21 +627,25 @@ deadline_insert_request(request_queue_t *q, struct request *rq,
        struct deadline_data *dd = q->elevator.elevator_data;
        struct deadline_rq *drq = RQ_DATA(rq);
 
-       if (unlikely(rq->flags & REQ_HARDBARRIER)) {
+       if (unlikely(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) {
                DL_INVALIDATE_HASH(dd);
                q->last_merge = NULL;
 
-               while (deadline_dispatch_requests(dd))
-                       ;
+               if (insert_here != dd->dispatch) {
+                       while (deadline_dispatch_requests(dd))
+                               ;
+               }
 
-               list_add_tail(&rq->queuelist, dd->dispatch);
-               return;
+               if (!insert_here)
+                       insert_here = dd->dispatch->prev;
        }
 
        if (unlikely(!blk_fs_request(rq))) {
                if (!insert_here)
-                       insert_here = dd->dispatch->prev;
+                       insert_here = dd->dispatch;
+       }
 
+       if (insert_here) {
                list_add(&rq->queuelist, insert_here);
                return;
        }

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
index 246c39a4962edca7e10ce6f2a8e3e8e521415c4f..4654fddecd7d5c9f9a755b1fff434ef6e85cc79d 100644 (file)
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -162,10 +162,10 @@ void elv_requeue_request(request_queue_t *q, struct request *rq)
 void __elv_add_request(request_queue_t *q, struct request *rq, int at_end,
                       int plug)
 {
-       struct list_head *insert = &q->queue_head;
+       struct list_head *insert = NULL;
 
-       if (at_end)
-               insert = insert->prev;
+       if (!at_end)
+               insert = &q->queue_head;
        if (plug)
                blk_plug_device(q);