linux-kernel - Re: [PATCH rdma-rc 3/3] IB/core: Fix ODP with IB_ACCESS

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Date:   Wed, 8 Jan 2020 17:24:19 +0200
From:   Yishai Hadas <yishaih@....mellanox.co.il>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Artemy Kovalyov <artemyko@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Yishai Hadas <yishaih@...lanox.com>,
        linux-kernel@...r.kernel.org, linux-next@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH rdma-rc 3/3] IB/core: Fix ODP with IB_ACCESS_HUGETLB
 handling

On 1/8/2020 2:56 PM, Geert Uytterhoeven wrote:
>      Hi Leon,
> 
> On Thu, 19 Dec 2019, Leon Romanovsky wrote:
>> From: Yishai Hadas <yishaih@...lanox.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@...lanox.com>
>> Reviewed-by: Artemy Kovalyov <artemyko@...lanox.com>
>> Reviewed-by: Aviad Yehezkel <aviadye@...lanox.com>
>> Signed-off-by: Leon Romanovsky <leonro@...lanox.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@...erman.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