On 04/11/2017 10:28 AM, Artur Paszkiewicz wrote:
> On 04/10/2017 09:09 PM, Shaohua Li wrote:
>>> +static void *ppl_io_pool_alloc(gfp_t gfp_mask, void *pool_data)
>>> +{
>>> + struct kmem_cache *kc = pool_data;
>>> + struct ppl_io_unit *io;
>>> +
>>> + io = kmem_cache_alloc(kc, gfp_mask);
>>> + if (!io)
>>> + return NULL;
>>> +
>>> + io->header_page = alloc_page(gfp_mask);
>>> + if (!io->header_page) {
>>> + kmem_cache_free(kc, io);
>>> + return NULL;
>>> + }
>>> +
>>> + return io;
>>
>> Maybe directly use GFP_NOWAIT here, we don't use other gfp
>
> Do you mean ignore the gfp_mask parameter? I don't think we should do
> that. It is provided by the mempool implementation. We only use
> GFP_NOWAIT for explicit allocations, but GFP_KERNEL is used for
> allocating initial items in mempool_create().
>
>>> +}
>>> +
>>> +static void ppl_io_pool_free(void *element, void *pool_data)
>>> +{
>>> + struct kmem_cache *kc = pool_data;
>>> + struct ppl_io_unit *io = element;
>>> +
>>> + __free_page(io->header_page);
>>> + kmem_cache_free(kc, io);
>>> +}
>>> +
>>> static struct ppl_io_unit *ppl_new_iounit(struct ppl_log *log,
>>> struct stripe_head *sh)
>>> {
>>> @@ -202,18 +228,19 @@ static struct ppl_io_unit *ppl_new_iounit(struct ppl_log *log,
>>> struct ppl_io_unit *io;
>>> struct ppl_header *pplhdr;
>>>
>>> - io = mempool_alloc(ppl_conf->io_pool, GFP_ATOMIC);
>>> + io = mempool_alloc(ppl_conf->io_pool, GFP_NOWAIT);
>>> if (!io)
>>> return NULL;
>>>
>>> - memset(io, 0, sizeof(*io));
>>> io->log = log;
>>> + io->entries_count = 0;
>>> + io->pp_size = 0;
>>> + io->submitted = false;
>>
>> I'd suggest moving the memset to ppl_io_pool_alloc. Don't think we need to
>> optimize to avoid setting header_page. And doing memset is less error prone,
>> for example adding new fields.
>
> OK, I'll change this and resend.
Well, on second thought, actually I can't move the memset to
ppl_io_pool_alloc. Mempool can use the preallocated elements, which are
then returned back to the pool after calling mempool_free() and can be
reused later. So a ppl_io_unit must be initialized after retrieving it
from mempool_alloc(). I can leave the memset in ppl_new_iounit() but
io->header_page pointer will have to be temporarily copied before
zeroing the iounit and then set back. Is this ok?
Thanks,
Artur
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