LinuxLists.cc - [PATCH 1/1] IB/umem: use get_user_pages

2019-11-09 02:05:31

Subject: [PATCH 1/1] IB/umem: use get_user_pages_fast() to pin DMA pages

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 <[email protected]>
Cc: Ira Weiny <[email protected]>
Signed-off-by: John Hubbard <[email protected]>
---
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

2019-11-11 03:22:56

by Ira Weiny

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Subject: Re: [PATCH 1/1] IB/umem: use get_user_pages_fast() to pin DMA pages

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 <[email protected]>
> Cc: Ira Weiny <[email protected]>

Reviewed-by: Ira Weiny <[email protected]>

> Signed-off-by: John Hubbard <[email protected]>
> ---
> 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
>

2019-11-11 21:48:39

by John Hubbard

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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 <[email protected]>
>> Cc: Ira Weiny <[email protected]>
>
> Reviewed-by: Ira Weiny <[email protected]>
>

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 <[email protected]>
>> ---
>> 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
>>
>

2019-11-12 20:34:43

by Jason Gunthorpe

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