[PATCH] stop elv_unregister() from rogering other iosched's data, fix locking

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 9 insertions, 15 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 24b702d649a9..0232df2b16e6 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -675,21 +675,15 @@ void elv_unregister(struct elevator_type *e)
         /*
          * Iterate every thread in the process to remove the io contexts.
          */
-        read_lock(&tasklist_lock);
-        do_each_thread(g, p) {
-                struct io_context *ioc = p->io_context;
-                if (ioc && ioc->cic) {
-                        ioc->cic->exit(ioc->cic);
-                        ioc->cic->dtor(ioc->cic);
-                        ioc->cic = NULL;
-                }
-                if (ioc && ioc->aic) {
-                        ioc->aic->exit(ioc->aic);
-                        ioc->aic->dtor(ioc->aic);
-                        ioc->aic = NULL;
-                }
-        } while_each_thread(g, p);
-        read_unlock(&tasklist_lock);
+        if (e->ops.trim) {
+                read_lock(&tasklist_lock);
+                do_each_thread(g, p) {
+                        task_lock(p);
+                        e->ops.trim(p->io_context);
+                        task_unlock(p);
+                } while_each_thread(g, p);
+                read_unlock(&tasklist_lock);
+        }
 
         spin_lock_irq(&elv_list_lock);
         list_del_init(&e->list);