[PATCH] block: remove per-disk debugfs files in blk_unregister_queue

Christoph Hellwig
2022-05-24T08:33:50Z

The block debugfs files are created in blk_register_queue, which is
called by add_disk and use a naming scheme based on the disk_name.
After del_gendisk returns that name can be reused and thus we must not
leave these debugfs files around, otherwise the kernel is unhappy
and spews messages like:

Directory XXXXX with parent 'block' already present!

and the newly created devices will not have working debugfs files.

Move the unregistration to blk_unregister_queue instead (which matches
the sysfs unregistration) to make sure the debugfs life time rules match
those of the disk name.

As part of the move also make sure the whole debugfs unregistration is
inside a single debugfs_mutex critical section.

Note that this breaks blktests block/002, which checks that the debugfs
directory has not been removed while blktests is running, but that
particular check should simply be removed from the test case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-mq-debugfs.c | 8 ++------
block/blk-mq-debugfs.h | 5 -----
block/blk-rq-qos.c | 2 --
block/blk-sysfs.c | 15 +++++++--------
kernel/trace/blktrace.c | 3 ---
5 files changed, 9 insertions(+), 24 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 7e4136a60e1cc..f7eaa5405e4b5 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -713,6 +713,8 @@ void blk_mq_debugfs_register(struct request_queue *q)

void blk_mq_debugfs_unregister(struct request_queue *q)
{
+ /* all entries were removed by the caller */
+ q->rqos_debugfs_dir = NULL;
q->sched_debugfs_dir = NULL;
}

@@ -833,12 +835,6 @@ void blk_mq_debugfs_register_rqos(struct rq_qos *rqos)
debugfs_create_files(rqos->debugfs_dir, rqos, rqos->ops->debugfs_attrs);
}

-void blk_mq_debugfs_unregister_queue_rqos(struct request_queue *q)
-{
- debugfs_remove_recursive(q->rqos_debugfs_dir);
- q->rqos_debugfs_dir = NULL;
-}
-
void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
struct blk_mq_hw_ctx *hctx)
{
diff --git a/block/blk-mq-debugfs.h b/block/blk-mq-debugfs.h
index 69918f4170d69..401e9e9da640b 100644
--- a/block/blk-mq-debugfs.h
+++ b/block/blk-mq-debugfs.h
@@ -36,7 +36,6 @@ void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx);

void blk_mq_debugfs_register_rqos(struct rq_qos *rqos);
void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos);
-void blk_mq_debugfs_unregister_queue_rqos(struct request_queue *q);
#else
static inline void blk_mq_debugfs_register(struct request_queue *q)
{
@@ -87,10 +86,6 @@ static inline void blk_mq_debugfs_register_rqos(struct rq_qos *rqos)
static inline void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos)
{
}
-
-static inline void blk_mq_debugfs_unregister_queue_rqos(struct request_queue *q)
-{
-}
#endif

#ifdef CONFIG_BLK_DEBUG_FS_ZONED
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index e83af7bc75919..d3a75693adbf4 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -294,8 +294,6 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,

void rq_qos_exit(struct request_queue *q)
{
- blk_mq_debugfs_unregister_queue_rqos(q);
-
while (q->rq_qos) {
struct rq_qos *rqos = q->rq_qos;
q->rq_qos = rqos->next;
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 88bd41d4cb593..c02fec8e9a3f6 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -779,14 +779,6 @@ static void blk_release_queue(struct kobject *kobj)
if (queue_is_mq(q))
blk_mq_release(q);

- blk_trace_shutdown(q);
- mutex_lock(&q->debugfs_mutex);
- debugfs_remove_recursive(q->debugfs_dir);
- mutex_unlock(&q->debugfs_mutex);
-
- if (queue_is_mq(q))
- blk_mq_debugfs_unregister(q);
-
bioset_exit(&q->bio_split);

if (blk_queue_has_srcu(q))
@@ -951,5 +943,12 @@ void blk_unregister_queue(struct gendisk *disk)

mutex_unlock(&q->sysfs_dir_lock);

+ mutex_lock(&q->debugfs_mutex);
+ blk_trace_shutdown(q);
+ debugfs_remove_recursive(q->debugfs_dir);
+ if (queue_is_mq(q))
+ blk_mq_debugfs_unregister(q);
+ mutex_unlock(&q->debugfs_mutex);
+
kobject_put(&disk_to_dev(disk)->kobj);
}
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 10a32b0f2deb6..fe04c6f96ca5d 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -770,14 +770,11 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
**/
void blk_trace_shutdown(struct request_queue *q)
{
- mutex_lock(&q->debugfs_mutex);
if (rcu_dereference_protected(q->blk_trace,
lockdep_is_held(&q->debugfs_mutex))) {
__blk_trace_startstop(q, 0);
__blk_trace_remove(q);
}
-
- mutex_unlock(&q->debugfs_mutex);
}

#ifdef CONFIG_BLK_CGROUP
--
2.30.2