netdev - Re: [PATCH v5 07/24] IB/umem: use get_user_pages

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Date:   Mon, 18 Nov 2019 10:49:18 +0100
From:   Jan Kara <jack@...e.cz>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Chinner <david@...morbit.com>,
        David Airlie <airlied@...ux.ie>,
        "David S . Miller" <davem@...emloft.net>,
        Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>,
        Jason Gunthorpe <jgg@...pe.ca>, Jens Axboe <axboe@...nel.dk>,
        Jonathan Corbet <corbet@....net>,
        Jérôme Glisse <jglisse@...hat.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Paul Mackerras <paulus@...ba.org>,
        Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, bpf@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, kvm@...r.kernel.org,
        linux-block@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-media@...r.kernel.org, linux-rdma@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...lanox.com>
Subject: Re: [PATCH v5 07/24] IB/umem: use get_user_pages_fast() to pin DMA
 pages

On Thu 14-11-19 21:53:23, 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.
> 
> Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
>  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
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR