Merge branch 'master' into gfs2

1 files changed, 74 insertions, 390 deletions

diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index c7ca9f0b6498..b7c5b34cb7b4 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -1,7 +1,7 @@
 /*
  *  Deadline i/o scheduler.
  *
- *  Copyright (C) 2002 Jens Axboe <axboe@suse.de>
+ *  Copyright (C) 2002 Jens Axboe <axboe@kernel.dk>
  */
 #include <linux/kernel.h>
 #include <linux/fs.h>
@@ -12,7 +12,6 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/compiler.h>
-#include <linux/hash.h>
 #include <linux/rbtree.h>
 
 /*
@@ -24,13 +23,6 @@ static const int writes_starved = 2;    /* max times reads can starve a write */
 static const int fifo_batch = 16;       /* # of sequential requests treated as one
                                      by the above parameters. For throughput. */
 
-static const int deadline_hash_shift = 5;
-#define DL_HASH_BLOCK(sec)      ((sec) >> 3)
-#define DL_HASH_FN(sec)         (hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
-#define DL_HASH_ENTRIES         (1 << deadline_hash_shift)
-#define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
-#define ON_HASH(drq)            (!hlist_unhashed(&(drq)->hash))
-
 struct deadline_data {
         /*
          * run time data
@@ -45,8 +37,7 @@ struct deadline_data {
         /*
          * next in sort order. read, write or both are NULL
          */
-        struct deadline_rq *next_drq[2];
-        struct hlist_head *hash;        /* request hash */
+        struct request *next_rq[2];
         unsigned int batching;          /* number of sequential requests made */
         sector_t last_sector;           /* head position */
         unsigned int starved;           /* times reads have starved writes */
@@ -58,240 +49,69 @@ struct deadline_data {
         int fifo_batch;
         int writes_starved;
         int front_merges;
-
-        mempool_t *drq_pool;
 };
 
-/*
- * pre-request data.
- */
-struct deadline_rq {
-        /*
-         * rbtree index, key is the starting offset
-         */
-        struct rb_node rb_node;
-        sector_t rb_key;
-
-        struct request *request;
-
-        /*
-         * request hash, key is the ending offset (for back merge lookup)
-         */
-        struct hlist_node hash;
-
-        /*
-         * expire fifo
-         */
-        struct list_head fifo;
-        unsigned long expires;
-};
-
-static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);
-
-static kmem_cache_t *drq_pool;
-
-#define RQ_DATA(rq)     ((struct deadline_rq *) (rq)->elevator_private)
+static void deadline_move_request(struct deadline_data *, struct request *);
 
-/*
- * the back merge hash support functions
- */
-static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
-{
-        hlist_del_init(&drq->hash);
-}
-
-static inline void deadline_del_drq_hash(struct deadline_rq *drq)
-{
-        if (ON_HASH(drq))
-                __deadline_del_drq_hash(drq);
-}
-
-static inline void
-deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
-{
-        struct request *rq = drq->request;
-
-        BUG_ON(ON_HASH(drq));
-
-        hlist_add_head(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
-}
-
-/*
- * move hot entry to front of chain
- */
-static inline void
-deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
-{
-        struct request *rq = drq->request;
-        struct hlist_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
-
-        if (ON_HASH(drq) && &drq->hash != head->first) {
-                hlist_del(&drq->hash);
-                hlist_add_head(&drq->hash, head);
-        }
-}
-
-static struct request *
-deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
-{
-        struct hlist_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
-        struct hlist_node *entry, *next;
-        struct deadline_rq *drq;
-
-        hlist_for_each_entry_safe(drq, entry, next, hash_list, hash) {
-                struct request *__rq = drq->request;
-
-                BUG_ON(!ON_HASH(drq));
-
-                if (!rq_mergeable(__rq)) {
-                        __deadline_del_drq_hash(drq);
-                        continue;
-                }
-
-                if (rq_hash_key(__rq) == offset)
-                        return __rq;
-        }
-
-        return NULL;
-}
-
-/*
- * rb tree support functions
- */
-#define rb_entry_drq(node)      rb_entry((node), struct deadline_rq, rb_node)
-#define DRQ_RB_ROOT(dd, drq)    (&(dd)->sort_list[rq_data_dir((drq)->request)])
-#define rq_rb_key(rq)           (rq)->sector
-
-static struct deadline_rq *
-__deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
-{
-        struct rb_node **p = &DRQ_RB_ROOT(dd, drq)->rb_node;
-        struct rb_node *parent = NULL;
-        struct deadline_rq *__drq;
-
-        while (*p) {
-                parent = *p;
-                __drq = rb_entry_drq(parent);
-
-                if (drq->rb_key < __drq->rb_key)
-                        p = &(*p)->rb_left;
-                else if (drq->rb_key > __drq->rb_key)
-                        p = &(*p)->rb_right;
-                else
-                        return __drq;
-        }
-
-        rb_link_node(&drq->rb_node, parent, p);
-        return NULL;
-}
+#define RQ_RB_ROOT(dd, rq)      (&(dd)->sort_list[rq_data_dir((rq))])
 
 static void
-deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
+deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
 {
-        struct deadline_rq *__alias;
-
-        drq->rb_key = rq_rb_key(drq->request);
+        struct rb_root *root = RQ_RB_ROOT(dd, rq);
+        struct request *__alias;
 
 retry:
-        __alias = __deadline_add_drq_rb(dd, drq);
-        if (!__alias) {
-                rb_insert_color(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
-                return;
+        __alias = elv_rb_add(root, rq);
+        if (unlikely(__alias)) {
+                deadline_move_request(dd, __alias);
+                goto retry;
         }
-
-        deadline_move_request(dd, __alias);
-        goto retry;
 }
 
 static inline void
-deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
+deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
 {
-        const int data_dir = rq_data_dir(drq->request);
+        const int data_dir = rq_data_dir(rq);
 
-        if (dd->next_drq[data_dir] == drq) {
-                struct rb_node *rbnext = rb_next(&drq->rb_node);
+        if (dd->next_rq[data_dir] == rq) {
+                struct rb_node *rbnext = rb_next(&rq->rb_node);
 
-                dd->next_drq[data_dir] = NULL;
+                dd->next_rq[data_dir] = NULL;
                 if (rbnext)
-                        dd->next_drq[data_dir] = rb_entry_drq(rbnext);
-        }
-
-        BUG_ON(!RB_EMPTY_NODE(&drq->rb_node));
-        rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
-        RB_CLEAR_NODE(&drq->rb_node);
-}
-
-static struct request *
-deadline_find_drq_rb(struct deadline_data *dd, sector_t sector, int data_dir)
-{
-        struct rb_node *n = dd->sort_list[data_dir].rb_node;
-        struct deadline_rq *drq;
-
-        while (n) {
-                drq = rb_entry_drq(n);
-
-                if (sector < drq->rb_key)
-                        n = n->rb_left;
-                else if (sector > drq->rb_key)
-                        n = n->rb_right;
-                else
-                        return drq->request;
+                        dd->next_rq[data_dir] = rb_entry_rq(rbnext);
         }
 
-        return NULL;
+        elv_rb_del(RQ_RB_ROOT(dd, rq), rq);
 }
 
 /*
- * deadline_find_first_drq finds the first (lowest sector numbered) request
- * for the specified data_dir. Used to sweep back to the start of the disk
- * (1-way elevator) after we process the last (highest sector) request.
- */
-static struct deadline_rq *
-deadline_find_first_drq(struct deadline_data *dd, int data_dir)
-{
-        struct rb_node *n = dd->sort_list[data_dir].rb_node;
-
-        for (;;) {
-                if (n->rb_left == NULL)
-                        return rb_entry_drq(n);
-                
-                n = n->rb_left;
-        }
-}
-
-/*
- * add drq to rbtree and fifo
+ * add rq to rbtree and fifo
  */
 static void
 deadline_add_request(struct request_queue *q, struct request *rq)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
-        struct deadline_rq *drq = RQ_DATA(rq);
+        const int data_dir = rq_data_dir(rq);
 
-        const int data_dir = rq_data_dir(drq->request);
+        deadline_add_rq_rb(dd, rq);
 
-        deadline_add_drq_rb(dd, drq);
         /*
          * set expire time (only used for reads) and add to fifo list
          */
-        drq->expires = jiffies + dd->fifo_expire[data_dir];
-        list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
-
-        if (rq_mergeable(rq))
-                deadline_add_drq_hash(dd, drq);
+        rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
+        list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
 }
 
 /*
- * remove rq from rbtree, fifo, and hash
+ * remove rq from rbtree and fifo.
  */
 static void deadline_remove_request(request_queue_t *q, struct request *rq)
 {
-        struct deadline_rq *drq = RQ_DATA(rq);
         struct deadline_data *dd = q->elevator->elevator_data;
 
-        list_del_init(&drq->fifo);
-        deadline_del_drq_rb(dd, drq);
-        deadline_del_drq_hash(drq);
+        rq_fifo_clear(rq);
+        deadline_del_rq_rb(dd, rq);
 }
 
 static int
@@ -302,27 +122,14 @@ deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
         int ret;
 
         /*
-         * see if the merge hash can satisfy a back merge
-         */
-        __rq = deadline_find_drq_hash(dd, bio->bi_sector);
-        if (__rq) {
-                BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
-
-                if (elv_rq_merge_ok(__rq, bio)) {
-                        ret = ELEVATOR_BACK_MERGE;
-                        goto out;
-                }
-        }
-
-        /*
          * check for front merge
          */
         if (dd->front_merges) {
-                sector_t rb_key = bio->bi_sector + bio_sectors(bio);
+                sector_t sector = bio->bi_sector + bio_sectors(bio);
 
-                __rq = deadline_find_drq_rb(dd, rb_key, bio_data_dir(bio));
+                __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
                 if (__rq) {
-                        BUG_ON(rb_key != rq_rb_key(__rq));
+                        BUG_ON(sector != __rq->sector);
 
                         if (elv_rq_merge_ok(__rq, bio)) {
                                 ret = ELEVATOR_FRONT_MERGE;
@@ -333,29 +140,21 @@ deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
 
         return ELEVATOR_NO_MERGE;
 out:
-        if (ret)
-                deadline_hot_drq_hash(dd, RQ_DATA(__rq));
         *req = __rq;
         return ret;
 }
 
-static void deadline_merged_request(request_queue_t *q, struct request *req)
+static void deadline_merged_request(request_queue_t *q, struct request *req,
+                                    int type)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
-        struct deadline_rq *drq = RQ_DATA(req);
-
-        /*
-         * hash always needs to be repositioned, key is end sector
-         */
-        deadline_del_drq_hash(drq);
-        deadline_add_drq_hash(dd, drq);
 
         /*
          * if the merge was a front merge, we need to reposition request
          */
-        if (rq_rb_key(req) != drq->rb_key) {
-                deadline_del_drq_rb(dd, drq);
-                deadline_add_drq_rb(dd, drq);
+        if (type == ELEVATOR_FRONT_MERGE) {
+                elv_rb_del(RQ_RB_ROOT(dd, req), req);
+                deadline_add_rq_rb(dd, req);
         }
 }
 
@@ -363,33 +162,14 @@ static void
 deadline_merged_requests(request_queue_t *q, struct request *req,
                          struct request *next)
 {
-        struct deadline_data *dd = q->elevator->elevator_data;
-        struct deadline_rq *drq = RQ_DATA(req);
-        struct deadline_rq *dnext = RQ_DATA(next);
-
-        BUG_ON(!drq);
-        BUG_ON(!dnext);
-
         /*
-         * reposition drq (this is the merged request) in hash, and in rbtree
-         * in case of a front merge
+         * if next expires before rq, assign its expire time to rq
+         * and move into next position (next will be deleted) in fifo
          */
-        deadline_del_drq_hash(drq);
-        deadline_add_drq_hash(dd, drq);
-
-        if (rq_rb_key(req) != drq->rb_key) {
-                deadline_del_drq_rb(dd, drq);
-                deadline_add_drq_rb(dd, drq);
-        }
-
-        /*
-         * if dnext expires before drq, assign its expire time to drq
-         * and move into dnext position (dnext will be deleted) in fifo
-         */
-        if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
-                if (time_before(dnext->expires, drq->expires)) {
-                        list_move(&drq->fifo, &dnext->fifo);
-                        drq->expires = dnext->expires;
+        if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
+                if (time_before(rq_fifo_time(next), rq_fifo_time(req))) {
+                        list_move(&req->queuelist, &next->queuelist);
+                        rq_set_fifo_time(req, rq_fifo_time(next));
                 }
         }
 
@@ -403,52 +183,50 @@ deadline_merged_requests(request_queue_t *q, struct request *req,
  * move request from sort list to dispatch queue.
  */
 static inline void
-deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
+deadline_move_to_dispatch(struct deadline_data *dd, struct request *rq)
 {
-        request_queue_t *q = drq->request->q;
+        request_queue_t *q = rq->q;
 
-        deadline_remove_request(q, drq->request);
-        elv_dispatch_add_tail(q, drq->request);
+        deadline_remove_request(q, rq);
+        elv_dispatch_add_tail(q, rq);
 }
 
 /*
  * move an entry to dispatch queue
  */
 static void
-deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
+deadline_move_request(struct deadline_data *dd, struct request *rq)
 {
-        const int data_dir = rq_data_dir(drq->request);
-        struct rb_node *rbnext = rb_next(&drq->rb_node);
+        const int data_dir = rq_data_dir(rq);
+        struct rb_node *rbnext = rb_next(&rq->rb_node);
 
-        dd->next_drq[READ] = NULL;
-        dd->next_drq[WRITE] = NULL;
+        dd->next_rq[READ] = NULL;
+        dd->next_rq[WRITE] = NULL;
 
         if (rbnext)
-                dd->next_drq[data_dir] = rb_entry_drq(rbnext);
+                dd->next_rq[data_dir] = rb_entry_rq(rbnext);
         
-        dd->last_sector = drq->request->sector + drq->request->nr_sectors;
+        dd->last_sector = rq->sector + rq->nr_sectors;
 
         /*
          * take it off the sort and fifo list, move
          * to dispatch queue
          */
-        deadline_move_to_dispatch(dd, drq);
+        deadline_move_to_dispatch(dd, rq);
 }
 
-#define list_entry_fifo(ptr)    list_entry((ptr), struct deadline_rq, fifo)
-
 /*
  * deadline_check_fifo returns 0 if there are no expired reads on the fifo,
  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
  */
 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
 {
-        struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
+        struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
 
         /*
-         * drq is expired!
+         * rq is expired!
          */
-        if (time_after(jiffies, drq->expires))
+        if (time_after(jiffies, rq_fifo_time(rq)))
                 return 1;
 
         return 0;
@@ -463,21 +241,21 @@ static int deadline_dispatch_requests(request_queue_t *q, int force)
         struct deadline_data *dd = q->elevator->elevator_data;
         const int reads = !list_empty(&dd->fifo_list[READ]);
         const int writes = !list_empty(&dd->fifo_list[WRITE]);
-        struct deadline_rq *drq;
+        struct request *rq;
         int data_dir;
 
         /*
          * batches are currently reads XOR writes
          */
-        if (dd->next_drq[WRITE])
-                drq = dd->next_drq[WRITE];
+        if (dd->next_rq[WRITE])
+                rq = dd->next_rq[WRITE];
         else
-                drq = dd->next_drq[READ];
+                rq = dd->next_rq[READ];
 
-        if (drq) {
+        if (rq) {
                 /* we have a "next request" */
                 
-                if (dd->last_sector != drq->request->sector)
+                if (dd->last_sector != rq->sector)
                         /* end the batch on a non sequential request */
                         dd->batching += dd->fifo_batch;
                 
@@ -526,30 +304,33 @@ dispatch_find_request:
         if (deadline_check_fifo(dd, data_dir)) {
                 /* An expired request exists - satisfy it */
                 dd->batching = 0;
-                drq = list_entry_fifo(dd->fifo_list[data_dir].next);
+                rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
                 
-        } else if (dd->next_drq[data_dir]) {
+        } else if (dd->next_rq[data_dir]) {
                 /*
                  * The last req was the same dir and we have a next request in
                  * sort order. No expired requests so continue on from here.
                  */
-                drq = dd->next_drq[data_dir];
+                rq = dd->next_rq[data_dir];
         } else {
+                struct rb_node *node;
                 /*
                  * The last req was the other direction or we have run out of
                  * higher-sectored requests. Go back to the lowest sectored
                  * request (1 way elevator) and start a new batch.
                  */
                 dd->batching = 0;
-                drq = deadline_find_first_drq(dd, data_dir);
+                node = rb_first(&dd->sort_list[data_dir]);
+                if (node)
+                        rq = rb_entry_rq(node);
         }
 
 dispatch_request:
         /*
-         * drq is the selected appropriate request.
+         * rq is the selected appropriate request.
          */
         dd->batching++;
-        deadline_move_request(dd, drq);
+        deadline_move_request(dd, rq);
 
         return 1;
 }
@@ -562,30 +343,6 @@ static int deadline_queue_empty(request_queue_t *q)
                 && list_empty(&dd->fifo_list[READ]);
 }
 
-static struct request *
-deadline_former_request(request_queue_t *q, struct request *rq)
-{
-        struct deadline_rq *drq = RQ_DATA(rq);
-        struct rb_node *rbprev = rb_prev(&drq->rb_node);
-
-        if (rbprev)
-                return rb_entry_drq(rbprev)->request;
-
-        return NULL;
-}
-
-static struct request *
-deadline_latter_request(request_queue_t *q, struct request *rq)
-{
-        struct deadline_rq *drq = RQ_DATA(rq);
-        struct rb_node *rbnext = rb_next(&drq->rb_node);
-
-        if (rbnext)
-                return rb_entry_drq(rbnext)->request;
-
-        return NULL;
-}
-
 static void deadline_exit_queue(elevator_t *e)
 {
         struct deadline_data *dd = e->elevator_data;
@@ -593,46 +350,21 @@ static void deadline_exit_queue(elevator_t *e)
         BUG_ON(!list_empty(&dd->fifo_list[READ]));
         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
 
-        mempool_destroy(dd->drq_pool);
-        kfree(dd->hash);
         kfree(dd);
 }
 
 /*
- * initialize elevator private data (deadline_data), and alloc a drq for
- * each request on the free lists
+ * initialize elevator private data (deadline_data).
  */
 static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
 {
         struct deadline_data *dd;
-        int i;
-
-        if (!drq_pool)
-                return NULL;
 
         dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
         if (!dd)
                 return NULL;
         memset(dd, 0, sizeof(*dd));
 
-        dd->hash = kmalloc_node(sizeof(struct hlist_head)*DL_HASH_ENTRIES,
-                                GFP_KERNEL, q->node);
-        if (!dd->hash) {
-                kfree(dd);
-                return NULL;
-        }
-
-        dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
-                                        mempool_free_slab, drq_pool, q->node);
-        if (!dd->drq_pool) {
-                kfree(dd->hash);
-                kfree(dd);
-                return NULL;
-        }
-
-        for (i = 0; i < DL_HASH_ENTRIES; i++)
-                INIT_HLIST_HEAD(&dd->hash[i]);
-
         INIT_LIST_HEAD(&dd->fifo_list[READ]);
         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
         dd->sort_list[READ] = RB_ROOT;
@@ -645,39 +377,6 @@ static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
         return dd;
 }
 
-static void deadline_put_request(request_queue_t *q, struct request *rq)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-        struct deadline_rq *drq = RQ_DATA(rq);
-
-        mempool_free(drq, dd->drq_pool);
-        rq->elevator_private = NULL;
-}
-
-static int
-deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
-                     gfp_t gfp_mask)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-        struct deadline_rq *drq;
-
-        drq = mempool_alloc(dd->drq_pool, gfp_mask);
-        if (drq) {
-                memset(drq, 0, sizeof(*drq));
-                RB_CLEAR_NODE(&drq->rb_node);
-                drq->request = rq;
-
-                INIT_HLIST_NODE(&drq->hash);
-
-                INIT_LIST_HEAD(&drq->fifo);
-
-                rq->elevator_private = drq;
-                return 0;
-        }
-
-        return 1;
-}
-
 /*
  * sysfs parts below
  */
@@ -757,10 +456,8 @@ static struct elevator_type iosched_deadline = {
                 .elevator_dispatch_fn =         deadline_dispatch_requests,
                 .elevator_add_req_fn =          deadline_add_request,
                 .elevator_queue_empty_fn =      deadline_queue_empty,
-                .elevator_former_req_fn =       deadline_former_request,
-                .elevator_latter_req_fn =       deadline_latter_request,
-                .elevator_set_req_fn =          deadline_set_request,
-                .elevator_put_req_fn =          deadline_put_request,
+                .elevator_former_req_fn =       elv_rb_former_request,
+                .elevator_latter_req_fn =       elv_rb_latter_request,
                 .elevator_init_fn =             deadline_init_queue,
                 .elevator_exit_fn =             deadline_exit_queue,
         },
@@ -772,24 +469,11 @@ static struct elevator_type iosched_deadline = {
 
 static int __init deadline_init(void)
 {
-        int ret;
-
-        drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
-                                     0, 0, NULL, NULL);
-
-        if (!drq_pool)
-                return -ENOMEM;
-
-        ret = elv_register(&iosched_deadline);
-        if (ret)
-                kmem_cache_destroy(drq_pool);
-
-        return ret;
+        return elv_register(&iosched_deadline);
 }
 
 static void __exit deadline_exit(void)
 {
-        kmem_cache_destroy(drq_pool);
         elv_unregister(&iosched_deadline);
 }