From: Omar Sandoval <osandov@xxxxxx>
CONFIG_DEBUG_TEST_DRIVER_REMOVE found a possible leak of q->rq_wb in a
couple of cases: when a request queue is reregistered and when gendisks
share a request_queue. This has been a problem since wbt was introduced,
but the WARN_ON(!list_empty(&stats->callbacks)) in the blk-stat rework
exposed it. The fix is unfortunately a hack until we fix all of the
drivers sharing a request_queue.
Fixes: 87760e5eef35 ("block: hook up writeback throttling")
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
---
block/blk-sysfs.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index fa831cb2fc30..a187e3f70028 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -893,7 +893,21 @@ int blk_register_queue(struct gendisk *disk)
kobject_uevent(&q->kobj, KOBJ_ADD);
- blk_wb_init(q);
+ /*
+ * There are two cases where wbt may have already been initialized:
+ * 1. A call sequence of blk_register_queue(); blk_unregister_queue();
+ * blk_register_queue().
+ * 2. Multiple gendisks sharing a request_queue.
+ *
+ * To fix case 1, we'd like to call wbt_exit() in
+ * blk_unregister_queue(). However, that's unsafe for case 2. So, we're
+ * forced to do this and call wbt_exit() in blk_release_queue() instead.
+ *
+ * Note that in case 2, wbt will account across disks until those legacy
+ * drivers are fixed.
+ */
+ if (!q->rq_wb)
+ blk_wb_init(q);
if (q->request_fn || (q->mq_ops && q->elevator)) {
ret = elv_register_queue(q);
--
2.12.1
