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    Subject[PATCH v2 28/47] bcache: dynamically allocate the md-bcache shrinker
    Date
    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..c176c7fc77d9 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_unregister(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 -ENOMEM;
    + }
    +
    + 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
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