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block: serialize all debugfs operations using q->debugfs_mutex 

Various places like I/O schedulers or the QOS infrastructure try to
register debugfs files on demans, which can race with creating and
removing the main queue debugfs directory.  Use the existing
debugfs_mutex to serialize all debugfs operations that rely on
q->debugfs_dir or the directories hanging off it.

To make the teardown code a little simpler declare all debugfs dentry
pointers and not just the main one uncoditionally in blkdev.h.

Move debugfs_mutex next to the dentries that it protects and document
what it is used for.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220614074827.458955-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-06-14 09:48:25 +02:00 committed by Jens Axboe
parent 50e34d7881
commit 5cf9c91ba9
8 changed files with 52 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
block/blk-mq-debugfs.c
View File

@ -711,11 +711,6 @@ void blk_mq_debugfs_register(struct request_queue *q)
}
}
void blk_mq_debugfs_unregister(struct request_queue *q)
{
q->sched_debugfs_dir = NULL;
}
static void blk_mq_debugfs_register_ctx(struct blk_mq_hw_ctx *hctx,
struct blk_mq_ctx *ctx)
{
@ -746,6 +741,8 @@ void blk_mq_debugfs_register_hctx(struct request_queue *q,
void blk_mq_debugfs_unregister_hctx(struct blk_mq_hw_ctx *hctx)
{
if (!hctx->queue->debugfs_dir)
return;
debugfs_remove_recursive(hctx->debugfs_dir);
hctx->sched_debugfs_dir = NULL;
hctx->debugfs_dir = NULL;
@ -773,6 +770,8 @@ void blk_mq_debugfs_register_sched(struct request_queue *q)
{
struct elevator_type *e = q->elevator->type;
lockdep_assert_held(&q->debugfs_mutex);
/*
* If the parent directory has not been created yet, return, we will be
* called again later on and the directory/files will be created then.
@ -790,6 +789,8 @@ void blk_mq_debugfs_register_sched(struct request_queue *q)
void blk_mq_debugfs_unregister_sched(struct request_queue *q)
{
lockdep_assert_held(&q->debugfs_mutex);
debugfs_remove_recursive(q->sched_debugfs_dir);
q->sched_debugfs_dir = NULL;
}
@ -811,6 +812,10 @@ static const char *rq_qos_id_to_name(enum rq_qos_id id)
void blk_mq_debugfs_unregister_rqos(struct rq_qos *rqos)
{
lockdep_assert_held(&rqos->q->debugfs_mutex);
if (!rqos->q->debugfs_dir)
return;
debugfs_remove_recursive(rqos->debugfs_dir);
rqos->debugfs_dir = NULL;
}
@ -820,6 +825,8 @@ void blk_mq_debugfs_register_rqos(struct rq_qos *rqos)
struct request_queue *q = rqos->q;
const char *dir_name = rq_qos_id_to_name(rqos->id);
lockdep_assert_held(&q->debugfs_mutex);
if (rqos->debugfs_dir || !rqos->ops->debugfs_attrs)
return;
@ -835,6 +842,8 @@ void blk_mq_debugfs_register_rqos(struct rq_qos *rqos)
void blk_mq_debugfs_unregister_queue_rqos(struct request_queue *q)
{
lockdep_assert_held(&q->debugfs_mutex);
debugfs_remove_recursive(q->rqos_debugfs_dir);
q->rqos_debugfs_dir = NULL;
}
@ -844,6 +853,8 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
{
struct elevator_type *e = q->elevator->type;
lockdep_assert_held(&q->debugfs_mutex);
/*
* If the parent debugfs directory has not been created yet, return;
* We will be called again later on with appropriate parent debugfs
@ -863,6 +874,10 @@ void blk_mq_debugfs_register_sched_hctx(struct request_queue *q,
void blk_mq_debugfs_unregister_sched_hctx(struct blk_mq_hw_ctx *hctx)
{
lockdep_assert_held(&hctx->queue->debugfs_mutex);
if (!hctx->queue->debugfs_dir)
return;
debugfs_remove_recursive(hctx->sched_debugfs_dir);
hctx->sched_debugfs_dir = NULL;
}

5
block/blk-mq-debugfs.h
View File

@ -21,7 +21,6 @@ int __blk_mq_debugfs_rq_show(struct seq_file *m, struct request *rq);
int blk_mq_debugfs_rq_show(struct seq_file *m, void *v);
void blk_mq_debugfs_register(struct request_queue *q);
void blk_mq_debugfs_unregister(struct request_queue *q);
void blk_mq_debugfs_register_hctx(struct request_queue *q,
struct blk_mq_hw_ctx *hctx);
void blk_mq_debugfs_unregister_hctx(struct blk_mq_hw_ctx *hctx);
@ -42,10 +41,6 @@ static inline void blk_mq_debugfs_register(struct request_queue *q)
{
}
static inline void blk_mq_debugfs_unregister(struct request_queue *q)
{
}
static inline void blk_mq_debugfs_register_hctx(struct request_queue *q,
struct blk_mq_hw_ctx *hctx)
{

11
block/blk-mq-sched.c
View File

@ -594,7 +594,9 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
if (ret)
goto err_free_map_and_rqs;
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_register_sched(q);
mutex_unlock(&q->debugfs_mutex);
queue_for_each_hw_ctx(q, hctx, i) {
if (e->ops.init_hctx) {
@ -607,7 +609,9 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
return ret;
}
}
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_register_sched_hctx(q, hctx);
mutex_unlock(&q->debugfs_mutex);
}
return 0;
@ -648,14 +652,21 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
unsigned int flags = 0;
queue_for_each_hw_ctx(q, hctx, i) {
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_unregister_sched_hctx(hctx);
mutex_unlock(&q->debugfs_mutex);
if (e->type->ops.exit_hctx && hctx->sched_data) {
e->type->ops.exit_hctx(hctx, i);
hctx->sched_data = NULL;
}
flags = hctx->flags;
}
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_unregister_sched(q);
mutex_unlock(&q->debugfs_mutex);
if (e->type->ops.exit_sched)
e->type->ops.exit_sched(e);
blk_mq_sched_tags_teardown(q, flags);

2
block/blk-rq-qos.c
View File

@ -294,7 +294,9 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,
void rq_qos_exit(struct request_queue *q)
{
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_unregister_queue_rqos(q);
mutex_unlock(&q->debugfs_mutex);
while (q->rq_qos) {
struct rq_qos *rqos = q->rq_qos;

7
block/blk-rq-qos.h
View File

@ -104,8 +104,11 @@ static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos)
blk_mq_unfreeze_queue(q);
if (rqos->ops->debugfs_attrs)
if (rqos->ops->debugfs_attrs) {
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_register_rqos(rqos);
mutex_unlock(&q->debugfs_mutex);
}
}
static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
@ -129,7 +132,9 @@ static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
blk_mq_unfreeze_queue(q);
mutex_lock(&q->debugfs_mutex);
blk_mq_debugfs_unregister_rqos(rqos);
mutex_unlock(&q->debugfs_mutex);
}
typedef bool (acquire_inflight_cb_t)(struct rq_wait *rqw, void *private_data);

20
block/blk-sysfs.c
View File

@ -779,14 +779,13 @@ 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);
blk_trace_shutdown(q);
debugfs_remove_recursive(q->debugfs_dir);
q->debugfs_dir = NULL;
q->sched_debugfs_dir = NULL;
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))
@ -836,17 +835,16 @@ int blk_register_queue(struct gendisk *disk)
goto unlock;
}
if (queue_is_mq(q))
__blk_mq_register_dev(dev, q);
mutex_lock(&q->sysfs_lock);
mutex_lock(&q->debugfs_mutex);
q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent),
blk_debugfs_root);
mutex_unlock(&q->debugfs_mutex);
if (queue_is_mq(q)) {
__blk_mq_register_dev(dev, q);
if (queue_is_mq(q))
blk_mq_debugfs_register(q);
}
mutex_lock(&q->sysfs_lock);
mutex_unlock(&q->debugfs_mutex);
ret = disk_register_independent_access_ranges(disk, NULL);
if (ret)

8
include/linux/blkdev.h
View File

@ -482,7 +482,6 @@ struct request_queue {
#endif /* CONFIG_BLK_DEV_ZONED */
int node;
struct mutex debugfs_mutex;
#ifdef CONFIG_BLK_DEV_IO_TRACE
struct blk_trace __rcu *blk_trace;
#endif
@ -526,11 +525,12 @@ struct request_queue {
struct bio_set bio_split;
struct dentry *debugfs_dir;
#ifdef CONFIG_BLK_DEBUG_FS
struct dentry *sched_debugfs_dir;
struct dentry *rqos_debugfs_dir;
#endif
/*
* Serializes all debugfs metadata operations using the above dentries.
*/
struct mutex debugfs_mutex;
bool mq_sysfs_init_done;

3
kernel/trace/blktrace.c
View File

@ -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