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Date: Tue, 4 Sep 2018 12:54:09 +0200
From: Matias Bjørling <mb@...htnvm.io>
To: hans.ml.holmberg@...tronix.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
javier@...xlabs.com, hans.holmberg@...xlabs.com
Subject: Re: [PATCH V2] lightnvm: pblk: stop recreating global caches
On 09/04/2018 12:38 PM, Hans Holmberg wrote:
> From: Hans Holmberg <hans.holmberg@...xlabs.com>
>
> Pblk should not create a set of global caches every time
> a pblk instance is created. The global caches should be
> made available only when there is one or more pblk instances.
>
> This patch bundles the global caches together with a kref
> keeping track of whether the caches should be available or not.
>
> Also, turn the global pblk lock into a mutex that explicitly
> protects the caches (as this was the only purpose of the lock).
>
> Signed-off-by: Hans Holmberg <hans.holmberg@...xlabs.com>
> ---
>
> Changes in V2:
> * Turned the pblk global lock into a mutex protecting the
> caches struct.
> * Renamed the global caches to pblk_caches
> * Refactored pblk_get_global_caches to handle only refcounting
> and locking.
>
> drivers/lightnvm/pblk-init.c | 132 ++++++++++++++++++++++++++++---------------
> 1 file changed, 86 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> index 9aebdee8e4c9..fb66bc84d5ca 100644
> --- a/drivers/lightnvm/pblk-init.c
> +++ b/drivers/lightnvm/pblk-init.c
> @@ -26,9 +26,24 @@ static unsigned int write_buffer_size;
> module_param(write_buffer_size, uint, 0644);
> MODULE_PARM_DESC(write_buffer_size, "number of entries in a write buffer");
>
> -static struct kmem_cache *pblk_ws_cache, *pblk_rec_cache, *pblk_g_rq_cache,
> - *pblk_w_rq_cache;
> -static DECLARE_RWSEM(pblk_lock);
> +struct pblk_global_caches {
> + struct kmem_cache *ws;
> + struct kmem_cache *rec;
> + struct kmem_cache *g_rq;
> + struct kmem_cache *w_rq;
> +
> + struct kref kref;
> +
> + struct mutex mutex; /* Ensures consistency between
> + * caches and kref
> + */
> +};
> +
> +static struct pblk_global_caches pblk_caches = {
> + .mutex = __MUTEX_INITIALIZER(pblk_caches.mutex),
> + .kref = KREF_INIT(0),
> +};
> +
> struct bio_set pblk_bio_set;
>
> static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
> @@ -307,53 +322,80 @@ static int pblk_set_addrf(struct pblk *pblk)
> return 0;
> }
>
> -static int pblk_init_global_caches(struct pblk *pblk)
> +static int pblk_create_global_caches(void)
> {
> - down_write(&pblk_lock);
> - pblk_ws_cache = kmem_cache_create("pblk_blk_ws",
> +
> + pblk_caches.ws = kmem_cache_create("pblk_blk_ws",
> sizeof(struct pblk_line_ws), 0, 0, NULL);
> - if (!pblk_ws_cache) {
> - up_write(&pblk_lock);
> + if (!pblk_caches.ws)
> return -ENOMEM;
> - }
>
> - pblk_rec_cache = kmem_cache_create("pblk_rec",
> + pblk_caches.rec = kmem_cache_create("pblk_rec",
> sizeof(struct pblk_rec_ctx), 0, 0, NULL);
> - if (!pblk_rec_cache) {
> - kmem_cache_destroy(pblk_ws_cache);
> - up_write(&pblk_lock);
> - return -ENOMEM;
> - }
> + if (!pblk_caches.rec)
> + goto fail_destroy_ws;
>
> - pblk_g_rq_cache = kmem_cache_create("pblk_g_rq", pblk_g_rq_size,
> + pblk_caches.g_rq = kmem_cache_create("pblk_g_rq", pblk_g_rq_size,
> 0, 0, NULL);
> - if (!pblk_g_rq_cache) {
> - kmem_cache_destroy(pblk_ws_cache);
> - kmem_cache_destroy(pblk_rec_cache);
> - up_write(&pblk_lock);
> - return -ENOMEM;
> - }
> + if (!pblk_caches.g_rq)
> + goto fail_destroy_rec;
>
> - pblk_w_rq_cache = kmem_cache_create("pblk_w_rq", pblk_w_rq_size,
> + pblk_caches.w_rq = kmem_cache_create("pblk_w_rq", pblk_w_rq_size,
> 0, 0, NULL);
> - if (!pblk_w_rq_cache) {
> - kmem_cache_destroy(pblk_ws_cache);
> - kmem_cache_destroy(pblk_rec_cache);
> - kmem_cache_destroy(pblk_g_rq_cache);
> - up_write(&pblk_lock);
> - return -ENOMEM;
> - }
> - up_write(&pblk_lock);
> + if (!pblk_caches.w_rq)
> + goto fail_destroy_g_rq;
>
> return 0;
> +
> +fail_destroy_g_rq:
> + kmem_cache_destroy(pblk_caches.g_rq);
> +fail_destroy_rec:
> + kmem_cache_destroy(pblk_caches.rec);
> +fail_destroy_ws:
> + kmem_cache_destroy(pblk_caches.ws);
> +
> + return -ENOMEM;
> +}
> +
> +static int pblk_get_global_caches(void)
> +{
> + int ret;
> +
> + mutex_lock(&pblk_caches.mutex);
> +
> + if (kref_read(&pblk_caches.kref) > 0) {
> + kref_get(&pblk_caches.kref);
> + mutex_unlock(&pblk_caches.mutex);
> + return 0;
> + }
> +
> + ret = pblk_create_global_caches();
> +
> + if (!ret)
> + kref_get(&pblk_caches.kref);
> +
> + mutex_unlock(&pblk_caches.mutex);
> +
> + return ret;
> +}
> +
> +static void pblk_destroy_global_caches(struct kref *ref)
> +{
> + struct pblk_global_caches *c;
> +
> + c = container_of(ref, struct pblk_global_caches, kref);
> +
> + kmem_cache_destroy(c->ws);
> + kmem_cache_destroy(c->rec);
> + kmem_cache_destroy(c->g_rq);
> + kmem_cache_destroy(c->w_rq);
> }
>
> -static void pblk_free_global_caches(struct pblk *pblk)
> +static void pblk_put_global_caches(void)
> {
> - kmem_cache_destroy(pblk_ws_cache);
> - kmem_cache_destroy(pblk_rec_cache);
> - kmem_cache_destroy(pblk_g_rq_cache);
> - kmem_cache_destroy(pblk_w_rq_cache);
> + mutex_lock(&pblk_caches.mutex);
> + kref_put(&pblk_caches.kref, pblk_destroy_global_caches);
> + mutex_unlock(&pblk_caches.mutex);
> }
>
> static int pblk_core_init(struct pblk *pblk)
> @@ -382,7 +424,7 @@ static int pblk_core_init(struct pblk *pblk)
> if (!pblk->pad_dist)
> return -ENOMEM;
>
> - if (pblk_init_global_caches(pblk))
> + if (pblk_get_global_caches())
> goto fail_free_pad_dist;
>
> /* Internal bios can be at most the sectors signaled by the device. */
> @@ -391,27 +433,27 @@ static int pblk_core_init(struct pblk *pblk)
> goto free_global_caches;
>
> ret = mempool_init_slab_pool(&pblk->gen_ws_pool, PBLK_GEN_WS_POOL_SIZE,
> - pblk_ws_cache);
> + pblk_caches.ws);
> if (ret)
> goto free_page_bio_pool;
>
> ret = mempool_init_slab_pool(&pblk->rec_pool, geo->all_luns,
> - pblk_rec_cache);
> + pblk_caches.rec);
> if (ret)
> goto free_gen_ws_pool;
>
> ret = mempool_init_slab_pool(&pblk->r_rq_pool, geo->all_luns,
> - pblk_g_rq_cache);
> + pblk_caches.g_rq);
> if (ret)
> goto free_rec_pool;
>
> ret = mempool_init_slab_pool(&pblk->e_rq_pool, geo->all_luns,
> - pblk_g_rq_cache);
> + pblk_caches.g_rq);
> if (ret)
> goto free_r_rq_pool;
>
> ret = mempool_init_slab_pool(&pblk->w_rq_pool, geo->all_luns,
> - pblk_w_rq_cache);
> + pblk_caches.w_rq);
> if (ret)
> goto free_e_rq_pool;
>
> @@ -457,7 +499,7 @@ static int pblk_core_init(struct pblk *pblk)
> free_page_bio_pool:
> mempool_exit(&pblk->page_bio_pool);
> free_global_caches:
> - pblk_free_global_caches(pblk);
> + pblk_put_global_caches();
> fail_free_pad_dist:
> kfree(pblk->pad_dist);
> return -ENOMEM;
> @@ -481,7 +523,7 @@ static void pblk_core_free(struct pblk *pblk)
> mempool_exit(&pblk->e_rq_pool);
> mempool_exit(&pblk->w_rq_pool);
>
> - pblk_free_global_caches(pblk);
> + pblk_put_global_caches();
> kfree(pblk->pad_dist);
> }
>
> @@ -1074,7 +1116,6 @@ static void pblk_exit(void *private, bool graceful)
> {
> struct pblk *pblk = private;
>
> - down_write(&pblk_lock);
> pblk_gc_exit(pblk, graceful);
> pblk_tear_down(pblk, graceful);
>
> @@ -1083,7 +1124,6 @@ static void pblk_exit(void *private, bool graceful)
> #endif
>
> pblk_free(pblk);
> - up_write(&pblk_lock);
> }
>
> static sector_t pblk_capacity(void *private)
>
Thanks. Applied for 4.20.
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