[PATCH 2/2] block: fix leak of q->rq_wb
From: Omar Sandoval <osandov@osandov.com>
Date: 2017-03-27 17:45:05
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
From: Omar Sandoval <redacted>
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 <redacted>
---
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