linux-kernel - Re: [PATCH 1/1] IB/umem: use get_user_pages

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Date:   Mon, 11 Nov 2019 13:44:07 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Ira Weiny <ira.weiny@...el.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>, <linux-rdma@...r.kernel.org>,
        <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] IB/umem: use get_user_pages_fast() to pin DMA pages

On 11/10/19 7:21 PM, Ira Weiny wrote:
> On Fri, Nov 08, 2019 at 06:04:34PM -0800, John Hubbard wrote:
>> And get rid of the mmap_sem calls, as part of that. Note
>> that get_user_pages_fast() will, if necessary, fall back to
>> __gup_longterm_unlocked(), which takes the mmap_sem as needed.
>>
>> Cc: Jason Gunthorpe <jgg@...pe.ca>
>> Cc: Ira Weiny <ira.weiny@...el.com>
> 
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> 

Thanks for the review, Ira! This will show up shortly, in the v3
series of "mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM".


thanks,
-- 
John Hubbard
NVIDIA

>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
>> ---
>>  drivers/infiniband/core/umem.c | 17 ++++++-----------
>>  1 file changed, 6 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
>> index 24244a2f68cc..3d664a2539eb 100644
>> --- a/drivers/infiniband/core/umem.c
>> +++ b/drivers/infiniband/core/umem.c
>> @@ -271,16 +271,13 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
>>  	sg = umem->sg_head.sgl;
>>  
>>  	while (npages) {
>> -		down_read(&mm->mmap_sem);
>> -		ret = get_user_pages(cur_base,
>> -				     min_t(unsigned long, npages,
>> -					   PAGE_SIZE / sizeof (struct page *)),
>> -				     gup_flags | FOLL_LONGTERM,
>> -				     page_list, NULL);
>> -		if (ret < 0) {
>> -			up_read(&mm->mmap_sem);
>> +		ret = get_user_pages_fast(cur_base,
>> +					  min_t(unsigned long, npages,
>> +						PAGE_SIZE /
>> +						sizeof(struct page *)),
>> +					  gup_flags | FOLL_LONGTERM, page_list);
>> +		if (ret < 0)
>>  			goto umem_release;
>> -		}
>>  
>>  		cur_base += ret * PAGE_SIZE;
>>  		npages   -= ret;
>> @@ -288,8 +285,6 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
>>  		sg = ib_umem_add_sg_table(sg, page_list, ret,
>>  			dma_get_max_seg_size(context->device->dma_device),
>>  			&umem->sg_nents);
>> -
>> -		up_read(&mm->mmap_sem);
>>  	}
>>  
>>  	sg_mark_end(sg);
>> -- 
>> 2.24.0
>>
>