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From:   Hans Holmberg <hans@owltronix.com>
Date:   Fri, 31 Aug 2018 12:02:25 +0200
Message-ID: <CANr-nt17oGKs9WtSQktQ0YTimFCV-4Afsmb7qw4Ynrj2QD6KpA@mail.gmail.com>
Subject: Re: [PATCH 4/7] lightnvm: pblk: move global caches to module init/exit
To:     Matias Bjorling <mb@lightnvm.io>
Cc:     linux-block@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Javier Gonzalez <javier@cnexlabs.com>,
        Hans Holmberg <hans.holmberg@cnexlabs.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Just sent a new patch ("lightnvm: pblk: stop recreating global
caches") which does reference counting.
On Wed, Aug 29, 2018 at 5:06 PM Hans Holmberg
<hans.ml.holmberg@owltronix.com> wrote:
>
> On Wed, Aug 29, 2018 at 3:29 PM Matias Bj=C3=B8rling <mb@lightnvm.io> wro=
te:
> >
> > On 08/29/2018 02:23 PM, Hans Holmberg wrote:
> > > From: Hans Holmberg <hans.holmberg@cnexlabs.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 insta=
nces.
> The global caches only need to exist when there is at least one pblk inst=
ance.
>
> Thanks,
> Hans
>
> >
> > > Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.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-ini=
t.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 entr=
ies in a write buffer");
> > >
> > >   static struct kmem_cache *pblk_ws_cache, *pblk_rec_cache, *pblk_g_r=
q_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 =3D 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 =3D 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 *p=
blk)
> > >       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 dev=
ice. */
> > >       ret =3D mempool_init_page_pool(&pblk->page_bio_pool, NVM_MAX_VL=
BA, 0);
> > >       if (ret)
> > > -             goto free_global_caches;
> > > +             goto free_pad_dist;
> > >
> > >       ret =3D 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 grace=
ful)
> > >   {
> > >       struct pblk *pblk =3D 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 grace=
ful)
> > >   #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 =3D bioset_init(&pblk_bio_set, BIO_POOL_SIZE, 0, 0);
> > >       if (ret)
> > >               return ret;
> > > +
> > >       ret =3D nvm_register_tgt_type(&tt_pblk);
> > >       if (ret)
> > > -             bioset_exit(&pblk_bio_set);
> > > +             goto fail_exit_bioset;
> > > +
> > > +     ret =3D 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);
> > >
> >