Re: [PATCH] null_blk: Register as a LightNVM device

[Matias BjÃrling]

On 11/11/2015 11:11 PM, Jens Axboe wrote:
> On 11/11/2015 02:27 PM, Jens Axboe wrote:
> > On 11/11/2015 03:06 AM, Matias BjÃrling wrote:
> > > Add support for registering as a LightNVM device. This allows us to
> > > evaluate the performance of the LightNVM library.
> > >
> > > In /drivers/Makefile, LightNVM is moved above block device drivers
> > > to make sure that the LightNVM media managers have been initialized
> > > before drivers under /drivers/block are initialized.
> >
> > Generally looks ok. One question:
> >
> > > +static void *null_lnvm_create_dma_pool(struct request_queue *q, char
> > > *name)
> > > +{
> > > +    mempool_t *virtmem_pool;
> > > +
> > > +    ppa_cache = kmem_cache_create(name, PAGE_SIZE, 0, 0, NULL);
> > > +    if (!ppa_cache) {
> > > +        pr_err("null_nvm: Unable to create kmem cache\n");
> > > +        return NULL;
> > > +    }
> > > +
> > > +    virtmem_pool = mempool_create_slab_pool(64, ppa_cache);
> > > +    if (!virtmem_pool) {
> > > +        pr_err("null_nvm: Unable to create virtual memory pool\n");
> > > +        return NULL;
> > > +    }
> > > +
> > > +    return virtmem_pool;
> > > +}
> >
> > Why create a slab cache if it's pages? Why not just have the mempool
> > alloc/free alloc single pages?
>
> Ala attached. Also fixes a leak of not freeing the ppa_cache slab cache.
> Did you try and load/reload the module? I'm thinking it would have crashed.

Good idea. I'll apply it. Thanks
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