Re: [PATCH rdma-rc 3/3] IB/core: Fix ODP with IB_ACCESS_HUGETLB handling

From: Yishai Hadas <yishaih@dev.mellanox.co.il>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Leon Romanovsky <leon@kernel.org>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@mellanox.com>,
	Leon Romanovsky <leonro@mellanox.com>,
	RDMA mailing list <linux-rdma@vger.kernel.org>,
	Artemy Kovalyov <artemyko@mellanox.com>,
	Aviad Yehezkel <aviadye@mellanox.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Yishai Hadas <yishaih@mellanox.com>,
	linux-kernel@vger.kernel.org, linux-next@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH rdma-rc 3/3] IB/core: Fix ODP with IB_ACCESS_HUGETLB handling
Date: Wed, 8 Jan 2020 17:24:19 +0200	[thread overview]
Message-ID: <ff4da6a1-609a-546c-e56c-e3ac529d4496@dev.mellanox.co.il> (raw)
In-Reply-To: <alpine.DEB.2.21.2001081352560.23971@ramsan.of.borg>

On 1/8/2020 2:56 PM, Geert Uytterhoeven wrote:
>      Hi Leon,
> 
> On Thu, 19 Dec 2019, Leon Romanovsky wrote:
>> From: Yishai Hadas <yishaih@mellanox.com>
>>
>> As VMAs for a given range might not be available as part of the
>> registration phase in ODP, IB_ACCESS_HUGETLB/page_shift must be checked
>> as part of the page fault flow.
>>
>> If the application didn't mmap the backed memory with huge pages or
>> released part of that hugepage area, an error will be set as part of the
>> page fault flow once be detected.
>>
>> Fixes: 0008b84ea9af ("IB/umem: Add support to huge ODP")
>> Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
>> Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
>> Reviewed-by: Aviad Yehezkel <aviadye@mellanox.com>
>> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> 
> Thanks for your patch!
> 
>> --- a/drivers/infiniband/core/umem_odp.c
>> +++ b/drivers/infiniband/core/umem_odp.c
>> @@ -241,22 +241,10 @@ struct ib_umem_odp *ib_umem_odp_get(struct 
>> ib_udata *udata, unsigned long addr,
>>     umem_odp->umem.owning_mm = mm = current->mm;
>>     umem_odp->notifier.ops = ops;
>>
>> -    umem_odp->page_shift = PAGE_SHIFT;
>> -    if (access & IB_ACCESS_HUGETLB) {
>> -        struct vm_area_struct *vma;
>> -        struct hstate *h;
>> -
>> -        down_read(&mm->mmap_sem);
>> -        vma = find_vma(mm, ib_umem_start(umem_odp));
>> -        if (!vma || !is_vm_hugetlb_page(vma)) {
>> -            up_read(&mm->mmap_sem);
>> -            ret = -EINVAL;
>> -            goto err_free;
>> -        }
>> -        h = hstate_vma(vma);
>> -        umem_odp->page_shift = huge_page_shift(h);
>> -        up_read(&mm->mmap_sem);
>> -    }
>> +    if (access & IB_ACCESS_HUGETLB)
>> +        umem_odp->page_shift = HPAGE_SHIFT;
>> +    else
>> +        umem_odp->page_shift = PAGE_SHIFT;
>>
>>     umem_odp->tgid = get_task_pid(current->group_leader, PIDTYPE_PID);
>>     ret = ib_init_umem_odp(umem_odp, ops);
> 
> noreply@ellerman.id.au reports for linux-next/m68k-allmodconfig/m68k:
> 
>      drivers/infiniband/core/umem_odp.c:245:26: error: 'HPAGE_SHIFT' 
> undeclared (first use in this function); did you mean 'PAGE_SHIFT'?
> 
> Should this depend on some HUGETLBFS option?
> 

Thanks for pointing on,
We would expect to use #ifdef CONFIG_HUGETLB_PAGE as done in below 
kernel code [1] that also used HPAGE_SHIFT.

I'll send some patch to 'for-next' to handle it.

[1] 
https://elixir.bootlin.com/linux/v5.3-rc7/source/drivers/misc/sgi-gru/grufault.c#L183