2023-07-27 08:22:49

by Qi Zheng

Subject: [PATCH v3 27/49] dm: dynamically allocate the dm-bufio shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the dm-bufio 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 dm_bufio_client.

Signed-off-by: Qi Zheng <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
---
drivers/md/dm-bufio.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index bc309e41d074..5a9124b83d53 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -963,7 +963,7 @@ struct dm_bufio_client {

sector_t start;

- struct shrinker shrinker;
+ struct shrinker *shrinker;
struct work_struct shrink_work;
atomic_long_t need_shrink;

@@ -2368,7 +2368,7 @@ static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink
{
struct dm_bufio_client *c;

- c = container_of(shrink, struct dm_bufio_client, shrinker);
+ c = shrink->private_data;
atomic_long_add(sc->nr_to_scan, &c->need_shrink);
queue_work(dm_bufio_wq, &c->shrink_work);

@@ -2377,7 +2377,7 @@ static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink

static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
- struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
+ struct dm_bufio_client *c = shrink->private_data;
unsigned long count = cache_total(&c->cache);
unsigned long retain_target = get_retain_buffers(c);
unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
@@ -2490,15 +2490,19 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
INIT_WORK(&c->shrink_work, shrink_work);
atomic_long_set(&c->need_shrink, 0);

- c->shrinker.count_objects = dm_bufio_shrink_count;
- c->shrinker.scan_objects = dm_bufio_shrink_scan;
- c->shrinker.seeks = 1;
- c->shrinker.batch = 0;
- r = register_shrinker(&c->shrinker, "dm-bufio:(%u:%u)",
- MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
- if (r)
+ c->shrinker = shrinker_alloc(0, "dm-bufio:(%u:%u)",
+ MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
+ if (!c->shrinker)
goto bad;

+ c->shrinker->count_objects = dm_bufio_shrink_count;
+ c->shrinker->scan_objects = dm_bufio_shrink_scan;
+ c->shrinker->seeks = 1;
+ c->shrinker->batch = 0;
+ c->shrinker->private_data = c;
+
+ shrinker_register(c->shrinker);
+
mutex_lock(&dm_bufio_clients_lock);
dm_bufio_client_count++;
list_add(&c->client_list, &dm_bufio_all_clients);
@@ -2537,7 +2541,7 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)

drop_buffers(c);

- unregister_shrinker(&c->shrinker);
+ shrinker_free(c->shrinker);
flush_work(&c->shrink_work);

mutex_lock(&dm_bufio_clients_lock);
--
2.30.2

2023-07-27 09:32:20

by Qi Zheng

Subject: Re: [PATCH v3 27/49] dm: dynamically allocate the dm-bufio shrinker

On 2023/7/27 16:04, Qi Zheng wrote:
> In preparation for implementing lockless slab shrink, use new APIs to
> dynamically allocate the dm-bufio 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 dm_bufio_client.
>
> Signed-off-by: Qi Zheng <[email protected]>
> Reviewed-by: Muchun Song <[email protected]>
> ---
> drivers/md/dm-bufio.c | 26 +++++++++++++++-----------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
> index bc309e41d074..5a9124b83d53 100644
> --- a/drivers/md/dm-bufio.c
> +++ b/drivers/md/dm-bufio.c
> @@ -963,7 +963,7 @@ struct dm_bufio_client {
>
> sector_t start;
>
> - struct shrinker shrinker;
> + struct shrinker *shrinker;
> struct work_struct shrink_work;
> atomic_long_t need_shrink;
>
> @@ -2368,7 +2368,7 @@ static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink
> {
> struct dm_bufio_client *c;
>
> - c = container_of(shrink, struct dm_bufio_client, shrinker);
> + c = shrink->private_data;
> atomic_long_add(sc->nr_to_scan, &c->need_shrink);
> queue_work(dm_bufio_wq, &c->shrink_work);
>
> @@ -2377,7 +2377,7 @@ static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink
>
> static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
> {
> - struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
> + struct dm_bufio_client *c = shrink->private_data;
> unsigned long count = cache_total(&c->cache);
> unsigned long retain_target = get_retain_buffers(c);
> unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
> @@ -2490,15 +2490,19 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
> INIT_WORK(&c->shrink_work, shrink_work);
> atomic_long_set(&c->need_shrink, 0);
>
> - c->shrinker.count_objects = dm_bufio_shrink_count;
> - c->shrinker.scan_objects = dm_bufio_shrink_scan;
> - c->shrinker.seeks = 1;
> - c->shrinker.batch = 0;
> - r = register_shrinker(&c->shrinker, "dm-bufio:(%u:%u)",
> - MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
> - if (r)
> + c->shrinker = shrinker_alloc(0, "dm-bufio:(%u:%u)",
> + MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
> + if (!c->shrinker)

Here should set r to -ENOMEM, will fix.

> goto bad;
>
> + c->shrinker->count_objects = dm_bufio_shrink_count;
> + c->shrinker->scan_objects = dm_bufio_shrink_scan;
> + c->shrinker->seeks = 1;
> + c->shrinker->batch = 0;
> + c->shrinker->private_data = c;
> +
> + shrinker_register(c->shrinker);
> +
> mutex_lock(&dm_bufio_clients_lock);
> dm_bufio_client_count++;
> list_add(&c->client_list, &dm_bufio_all_clients);
> @@ -2537,7 +2541,7 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
>
> drop_buffers(c);
>
> - unregister_shrinker(&c->shrinker);
> + shrinker_free(c->shrinker);
> flush_work(&c->shrink_work);
>
> mutex_lock(&dm_bufio_clients_lock);