[PATCH v4 29/48] bcache: dynamically allocate the md-bcache shrinker

Qi Zheng
2023-08-07T11:36:14Z

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the md-bcache 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 cache_set.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
drivers/md/bcache/bcache.h | 2 +-
drivers/md/bcache/btree.c | 27 ++++++++++++++++-----------
drivers/md/bcache/sysfs.c | 3 ++-
3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 5a79bb3c272f..c622bc50f81b 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -541,7 +541,7 @@ struct cache_set {
struct bio_set bio_split;

/* For the btree cache */
- struct shrinker shrink;
+ struct shrinker *shrink;

/* For the btree cache and anything allocation related */
struct mutex bucket_lock;
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index fd121a61f17c..ae5cbb55861f 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -667,7 +667,7 @@ static int mca_reap(struct btree *b, unsigned int min_order, bool flush)
static unsigned long bch_mca_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+ struct cache_set *c = shrink->private_data;
struct btree *b, *t;
unsigned long i, nr = sc->nr_to_scan;
unsigned long freed = 0;
@@ -734,7 +734,7 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
static unsigned long bch_mca_count(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+ struct cache_set *c = shrink->private_data;

if (c->shrinker_disabled)
return 0;
@@ -752,8 +752,8 @@ void bch_btree_cache_free(struct cache_set *c)

closure_init_stack(&cl);

- if (c->shrink.list.next)
- unregister_shrinker(&c->shrink);
+ if (c->shrink)
+ shrinker_free(c->shrink);

mutex_lock(&c->bucket_lock);

@@ -828,14 +828,19 @@ int bch_btree_cache_alloc(struct cache_set *c)
c->verify_data = NULL;
#endif

- c->shrink.count_objects = bch_mca_count;
- c->shrink.scan_objects = bch_mca_scan;
- c->shrink.seeks = 4;
- c->shrink.batch = c->btree_pages * 2;
+ c->shrink = shrinker_alloc(0, "md-bcache:%pU", c->set_uuid);
+ if (!c->shrink) {
+ pr_warn("bcache: %s: could not allocate shrinker\n", __func__);
+ return 0;
+ }
+
+ c->shrink->count_objects = bch_mca_count;
+ c->shrink->scan_objects = bch_mca_scan;
+ c->shrink->seeks = 4;
+ c->shrink->batch = c->btree_pages * 2;
+ c->shrink->private_data = c;

- if (register_shrinker(&c->shrink, "md-bcache:%pU", c->set_uuid))
- pr_warn("bcache: %s: could not register shrinker\n",
- __func__);
+ shrinker_register(c->shrink);

return 0;
}
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 0e2c1880f60b..45d8af755de6 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -866,7 +866,8 @@ STORE(__bch_cache_set)

sc.gfp_mask = GFP_KERNEL;
sc.nr_to_scan = strtoul_or_return(buf);
- c->shrink.scan_objects(&c->shrink, &sc);
+ if (c->shrink)
+ c->shrink->scan_objects(c->shrink, &sc);
}

sysfs_strtoul_clamp(congested_read_threshold_us,
--
2.30.2