From: John Hubbard <jhubbard@nvidia.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Dave Chinner" <david@fromorbit.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Jérôme Glisse" <jglisse@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-rdma@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote()
Date: Mon, 12 Aug 2019 17:07:32 -0700 [thread overview]
Message-ID: <38d2ff2f-4a69-e8bd-8f7c-41f1dbd80fae@nvidia.com> (raw)
In-Reply-To: <20190812234950.GA6455@iweiny-DESK2.sc.intel.com>
On 8/12/19 4:49 PM, Ira Weiny wrote:
> On Sun, Aug 11, 2019 at 06:50:44PM -0700, john.hubbard@gmail.com wrote:
>> From: John Hubbard <jhubbard@nvidia.com>
...
>> diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
>> index 53085896d718..fdff034a8a30 100644
>> --- a/drivers/infiniband/core/umem_odp.c
>> +++ b/drivers/infiniband/core/umem_odp.c
>> @@ -534,7 +534,7 @@ static int ib_umem_odp_map_dma_single_page(
>> }
>>
>> out:
>> - put_user_page(page);
>> + vaddr_unpin_pages(&page, 1, &umem_odp->umem.vaddr_pin);
>>
>> if (remove_existing_mapping) {
>> ib_umem_notifier_start_account(umem_odp);
>> @@ -635,9 +635,10 @@ int ib_umem_odp_map_dma_pages(struct ib_umem_odp *umem_odp, u64 user_virt,
>> * complex (and doesn't gain us much performance in most use
>> * cases).
>> */
>> - npages = get_user_pages_remote(owning_process, owning_mm,
>> + npages = vaddr_pin_pages_remote(owning_process, owning_mm,
>> user_virt, gup_num_pages,
>> - flags, local_page_list, NULL, NULL);
>> + flags, local_page_list, NULL, NULL,
>> + &umem_odp->umem.vaddr_pin);
>
> Thinking about this part of the patch... is this pin really necessary? This
> code is not doing a long term pin. The page just needs a reference while we
> map it into the devices page tables. Once that is done we should get notifiers
> if anything changes and we can adjust. right?
>
OK, now it's a little interesting: the FOLL_PIN is necessary, but maybe not
FOLL_LONGTERM. Illustrating once again that it's actually necessary to allow
these flags to vary independently.
And that leads to another API refinement idea: let's set FOLL_PIN within the
vaddr_pin_pages*() wrappers, and set FOLL_LONGTER in the *callers* of those
wrappers, yes?
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-08-13 0:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-12 1:50 [RFC PATCH 0/2] mm/gup: introduce vaddr_pin_pages_remote(), FOLL_PIN john.hubbard
2019-08-12 1:50 ` [RFC PATCH 1/2] mm/gup: introduce FOLL_PIN flag for get_user_pages() john.hubbard
2019-08-12 1:50 ` [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote() john.hubbard
2019-08-12 22:03 ` Ira Weiny
2019-08-12 22:21 ` John Hubbard
2019-08-12 23:49 ` Ira Weiny
2019-08-13 0:07 ` John Hubbard [this message]
2019-08-13 21:08 ` Ira Weiny
2019-08-14 0:51 ` John Hubbard
2019-08-14 0:56 ` John Hubbard
2019-08-14 23:50 ` Ira Weiny
2019-08-15 0:02 ` John Hubbard
2019-08-15 3:01 ` John Hubbard
2019-08-15 13:26 ` Jan Kara
2019-08-15 13:35 ` Jan Kara
2019-08-15 14:51 ` Jason Gunthorpe
2019-08-15 17:32 ` Ira Weiny
2019-08-15 17:41 ` John Hubbard
2019-08-16 2:14 ` John Hubbard
2019-08-16 15:41 ` Jan Kara
2019-08-16 18:33 ` Ira Weiny
2019-08-16 18:50 ` John Hubbard
2019-08-16 21:59 ` Ira Weiny
2019-08-16 22:36 ` John Hubbard
2019-08-16 8:47 ` Vlastimil Babka
2019-08-16 15:44 ` Jan Kara
2019-08-16 15:52 ` Jerome Glisse
2019-08-16 16:13 ` Jan Kara
2019-08-16 16:31 ` Jason Gunthorpe
2019-08-16 16:54 ` Jerome Glisse
2019-08-16 17:04 ` Jason Gunthorpe
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