cfq-iosched: add hlist for browsing parallel to the radix tree

It's cumbersome to browse a radix tree from start to finish, especially
since we modify keys when a process exits. So add a hlist for the single
purpose of browsing over all known cfq_io_contexts, used for exit,
io prio change, etc.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=9948

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 12 insertions, 26 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ca198e61fa65..0f962ecae91f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1145,38 +1145,19 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
 /*
  * Call func for each cic attached to this ioc. Returns number of cic's seen.
  */
-#define CIC_GANG_NR     16
 static unsigned int
 call_for_each_cic(struct io_context *ioc,
                   void (*func)(struct io_context *, struct cfq_io_context *))
 {
-        struct cfq_io_context *cics[CIC_GANG_NR];
-        unsigned long index = 0;
-        unsigned int called = 0;
-        int nr;
+        struct cfq_io_context *cic;
+        struct hlist_node *n;
+        int called = 0;
 
         rcu_read_lock();
-
-        do {
-                int i;
-
-                /*
-                 * Perhaps there's a better way - this just gang lookups from
-                 * 0 to the end, restarting after each CIC_GANG_NR from the
-                 * last key + 1.
-                 */
-                nr = radix_tree_gang_lookup(&ioc->radix_root, (void **) cics,
-                                                index, CIC_GANG_NR);
-                if (!nr)
-                        break;
-
-                called += nr;
-                index = 1 + (unsigned long) cics[nr - 1]->key;
-
-                for (i = 0; i < nr; i++)
-                        func(ioc, cics[i]);
-        } while (nr == CIC_GANG_NR);
-
+        hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) {
+                func(ioc, cic);
+                called++;
+        }
         rcu_read_unlock();
 
         return called;
@@ -1190,6 +1171,7 @@ static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
 
         spin_lock_irqsave(&ioc->lock, flags);
         radix_tree_delete(&ioc->radix_root, cic->dead_key);
+        hlist_del_rcu(&cic->cic_list);
         spin_unlock_irqrestore(&ioc->lock, flags);
 
         kmem_cache_free(cfq_ioc_pool, cic);
@@ -1280,6 +1262,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
         if (cic) {
                 cic->last_end_request = jiffies;
                 INIT_LIST_HEAD(&cic->queue_list);
+                INIT_HLIST_NODE(&cic->cic_list);
                 cic->dtor = cfq_free_io_context;
                 cic->exit = cfq_exit_io_context;
                 elv_ioc_count_inc(ioc_count);
@@ -1501,6 +1484,7 @@ cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
                 rcu_assign_pointer(ioc->ioc_data, NULL);
 
         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
+        hlist_del_rcu(&cic->cic_list);
         spin_unlock_irqrestore(&ioc->lock, flags);
 
         cfq_cic_free(cic);
@@ -1561,6 +1545,8 @@ static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
                 spin_lock_irqsave(&ioc->lock, flags);
                 ret = radix_tree_insert(&ioc->radix_root,
                                                 (unsigned long) cfqd, cic);
+                if (!ret)
+                        hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
                 spin_unlock_irqrestore(&ioc->lock, flags);
 
                 radix_tree_preload_end();