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, 15 insertions, 20 deletions

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 4ae0929c6e38..e34df7c9fc36 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -17,17 +17,13 @@ static struct kmem_cache *iocontext_cachep;
 
 static void cfq_dtor(struct io_context *ioc)
 {
-        struct cfq_io_context *cic[1];
-        int r;
+        if (!hlist_empty(&ioc->cic_list)) {
+                struct cfq_io_context *cic;
 
-        /*
-         * We don't have a specific key to lookup with, so use the gang
-         * lookup to just retrieve the first item stored. The cfq exit
-         * function will iterate the full tree, so any member will do.
-         */
-        r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
-        if (r > 0)
-                cic[0]->dtor(ioc);
+                cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
+                                                                cic_list);
+                cic->dtor(ioc);
+        }
 }
 
 /*
@@ -57,18 +53,16 @@ EXPORT_SYMBOL(put_io_context);
 
 static void cfq_exit(struct io_context *ioc)
 {
-        struct cfq_io_context *cic[1];
-        int r;
-
         rcu_read_lock();
-        /*
-         * See comment for cfq_dtor()
-         */
-        r = radix_tree_gang_lookup(&ioc->radix_root, (void **) cic, 0, 1);
-        rcu_read_unlock();
 
-        if (r > 0)
-                cic[0]->exit(ioc);
+        if (!hlist_empty(&ioc->cic_list)) {
+                struct cfq_io_context *cic;
+
+                cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
+                                                                cic_list);
+                cic->exit(ioc);
+        }
+        rcu_read_unlock();
 }
 
 /* Called by the exitting task */
@@ -105,6 +99,7 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
                 ret->nr_batch_requests = 0; /* because this is 0 */
                 ret->aic = NULL;
                 INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
+                INIT_HLIST_HEAD(&ret->cic_list);
                 ret->ioc_data = NULL;
         }