[PATCH v4 28/48] md/raid5: dynamically allocate the md-raid5 shrinker

Qi Zheng
2023-08-07T11:36:36Z

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the md-raid5 shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct r5conf.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
---
drivers/md/raid5.c | 26 +++++++++++++++-----------
drivers/md/raid5.h | 2 +-
2 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 32a87193bad7..e284c2f7dbe4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7401,7 +7401,7 @@ static void free_conf(struct r5conf *conf)

log_exit(conf);

- unregister_shrinker(&conf->shrinker);
+ shrinker_free(conf->shrinker);
free_thread_groups(conf);
shrink_stripes(conf);
raid5_free_percpu(conf);
@@ -7449,7 +7449,7 @@ static int raid5_alloc_percpu(struct r5conf *conf)
static unsigned long raid5_cache_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+ struct r5conf *conf = shrink->private_data;
unsigned long ret = SHRINK_STOP;

if (mutex_trylock(&conf->cache_size_mutex)) {
@@ -7470,7 +7470,7 @@ static unsigned long raid5_cache_scan(struct shrinker *shrink,
static unsigned long raid5_cache_count(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+ struct r5conf *conf = shrink->private_data;

if (conf->max_nr_stripes < conf->min_nr_stripes)
/* unlikely, but not impossible */
@@ -7705,18 +7705,22 @@ static struct r5conf *setup_conf(struct mddev *mddev)
* it reduces the queue depth and so can hurt throughput.
* So set it rather large, scaled by number of devices.
*/
- conf->shrinker.seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
- conf->shrinker.scan_objects = raid5_cache_scan;
- conf->shrinker.count_objects = raid5_cache_count;
- conf->shrinker.batch = 128;
- conf->shrinker.flags = 0;
- ret = register_shrinker(&conf->shrinker, "md-raid5:%s", mdname(mddev));
- if (ret) {
- pr_warn("md/raid:%s: couldn't register shrinker.\n",
+ conf->shrinker = shrinker_alloc(0, "md-raid5:%s", mdname(mddev));
+ if (!conf->shrinker) {
+ ret = -ENOMEM;
+ pr_warn("md/raid:%s: couldn't allocate shrinker.\n",
mdname(mddev));
goto abort;
}

+ conf->shrinker->seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
+ conf->shrinker->scan_objects = raid5_cache_scan;
+ conf->shrinker->count_objects = raid5_cache_count;
+ conf->shrinker->batch = 128;
+ conf->shrinker->private_data = conf;
+
+ shrinker_register(conf->shrinker);
+
sprintf(pers_name, "raid%d", mddev->new_level);
rcu_assign_pointer(conf->thread,
md_register_thread(raid5d, mddev, pers_name));
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 97a795979a35..22bea20eccbd 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -670,7 +670,7 @@ struct r5conf {
wait_queue_head_t wait_for_stripe;
wait_queue_head_t wait_for_overlap;
unsigned long cache_state;
- struct shrinker shrinker;
+ struct shrinker *shrinker;
int pool_size; /* number of disks in stripeheads in pool */
spinlock_t device_lock;
struct disk_info *disks;
--
2.30.2