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SubjectRe: [PATCH v3 29/49] md/raid5: dynamically allocate the md-raid5 shrinker
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On 2023/7/27 16:04, Qi Zheng wrote:
> 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 | 25 ++++++++++++++-----------
> drivers/md/raid5.h | 2 +-
> 2 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 85b3004594e0..fbb4e6f5ff43 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -7414,7 +7414,7 @@ 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);
> @@ -7462,7 +7462,7 @@ 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)) {
> @@ -7483,7 +7483,7 @@ 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 */
> @@ -7718,18 +7718,21 @@ 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) {

Here should set ret to -ENOMEM, will fix.

> + 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;

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