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Date:   Wed, 29 Aug 2018 17:06:18 +0200
From:   Hans Holmberg <hans.ml.holmberg@...tronix.com>
To:     Matias Bjorling <mb@...htnvm.io>
Cc:     linux-block@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Javier Gonzalez <javier@...xlabs.com>,
        Hans Holmberg <hans.holmberg@...xlabs.com>
Subject: Re: [PATCH 4/7] lightnvm: pblk: move global caches to module init/exit

On Wed, Aug 29, 2018 at 3:29 PM Matias Bjørling <mb@...htnvm.io> wrote:
>
> On 08/29/2018 02:23 PM, Hans Holmberg wrote:
> > From: Hans Holmberg <hans.holmberg@...xlabs.com>
> >
> > Pblk's global caches should not be initialized every time
> > a pblk instance is created, so move the creation and destruction
> > of the caches to module init/exit.
> >
> > Also remove the global pblk lock as it is no longer needed after
> > the move.
> >
>
> The original goal was to not allocate memory for the caches unless a
> pblk instance was initialized. This instead uses up memory without pblk
> being used, which I don't think is a good idea.

You're right, i'll rework the patch with reference counting of pblk instances.
The global caches only need to exist when there is at least one pblk instance.

Thanks,
Hans

>
> > Signed-off-by: Hans Holmberg <hans.holmberg@...xlabs.com>
> > ---
> >   drivers/lightnvm/pblk-init.c | 42 ++++++++++++++++++++----------------------
> >   1 file changed, 20 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> > index 76a4a271b9cf..0be64220b5d8 100644
> > --- a/drivers/lightnvm/pblk-init.c
> > +++ b/drivers/lightnvm/pblk-init.c
> > @@ -27,7 +27,6 @@ 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 bio_set pblk_bio_set;
> >
> >   static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
> > @@ -306,21 +305,17 @@ static int pblk_set_addrf(struct pblk *pblk)
> >       return 0;
> >   }
> >
> > -static int pblk_init_global_caches(struct pblk *pblk)
> > +static int pblk_init_global_caches(void)
> >   {
> > -     down_write(&pblk_lock);
> >       pblk_ws_cache = kmem_cache_create("pblk_blk_ws",
> >                               sizeof(struct pblk_line_ws), 0, 0, NULL);
> > -     if (!pblk_ws_cache) {
> > -             up_write(&pblk_lock);
> > +     if (!pblk_ws_cache)
> >               return -ENOMEM;
> > -     }
> >
> >       pblk_rec_cache = 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;
> >       }
> >
> > @@ -329,7 +324,6 @@ static int pblk_init_global_caches(struct pblk *pblk)
> >       if (!pblk_g_rq_cache) {
> >               kmem_cache_destroy(pblk_ws_cache);
> >               kmem_cache_destroy(pblk_rec_cache);
> > -             up_write(&pblk_lock);
> >               return -ENOMEM;
> >       }
> >
> > @@ -339,15 +333,13 @@ static int pblk_init_global_caches(struct pblk *pblk)
> >               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);
> >
> >       return 0;
> >   }
> >
> > -static void pblk_free_global_caches(struct pblk *pblk)
> > +static void pblk_free_global_caches(void)
> >   {
> >       kmem_cache_destroy(pblk_ws_cache);
> >       kmem_cache_destroy(pblk_rec_cache);
> > @@ -381,13 +373,10 @@ static int pblk_core_init(struct pblk *pblk)
> >       if (!pblk->pad_dist)
> >               return -ENOMEM;
> >
> > -     if (pblk_init_global_caches(pblk))
> > -             goto fail_free_pad_dist;
> > -
> >       /* Internal bios can be at most the sectors signaled by the device. */
> >       ret = mempool_init_page_pool(&pblk->page_bio_pool, NVM_MAX_VLBA, 0);
> >       if (ret)
> > -             goto free_global_caches;
> > +             goto free_pad_dist;
> >
> >       ret = mempool_init_slab_pool(&pblk->gen_ws_pool, PBLK_GEN_WS_POOL_SIZE,
> >                                    pblk_ws_cache);
> > @@ -455,9 +444,7 @@ static int pblk_core_init(struct pblk *pblk)
> >       mempool_exit(&pblk->gen_ws_pool);
> >   free_page_bio_pool:
> >       mempool_exit(&pblk->page_bio_pool);
> > -free_global_caches:
> > -     pblk_free_global_caches(pblk);
> > -fail_free_pad_dist:
> > +free_pad_dist:
> >       kfree(pblk->pad_dist);
> >       return -ENOMEM;
> >   }
> > @@ -480,7 +467,6 @@ 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);
> >       kfree(pblk->pad_dist);
> >   }
> >
> > @@ -1067,7 +1053,6 @@ 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);
> >
> > @@ -1076,7 +1061,6 @@ static void pblk_exit(void *private, bool graceful)
> >   #endif
> >
> >       pblk_free(pblk);
> > -     up_write(&pblk_lock);
> >   }
> >
> >   static sector_t pblk_capacity(void *private)
> > @@ -1237,9 +1221,22 @@ static int __init pblk_module_init(void)
> >       ret = bioset_init(&pblk_bio_set, BIO_POOL_SIZE, 0, 0);
> >       if (ret)
> >               return ret;
> > +
> >       ret = nvm_register_tgt_type(&tt_pblk);
> >       if (ret)
> > -             bioset_exit(&pblk_bio_set);
> > +             goto fail_exit_bioset;
> > +
> > +     ret = pblk_init_global_caches();
> > +     if (ret)
> > +             goto fail_unregister_tgt_type;
> > +
> > +     return 0;
> > +
> > +fail_unregister_tgt_type:
> > +     nvm_unregister_tgt_type(&tt_pblk);
> > +fail_exit_bioset:
> > +     bioset_exit(&pblk_bio_set);
> > +
> >       return ret;
> >   }
> >
> > @@ -1247,6 +1244,7 @@ static void pblk_module_exit(void)
> >   {
> >       bioset_exit(&pblk_bio_set);
> >       nvm_unregister_tgt_type(&tt_pblk);
> > +     pblk_free_global_caches();
> >   }
> >
> >   module_init(pblk_module_init);
> >
>

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