* [PATCH v2 0/2] IB/umem: use get_user_pages_fast() to pin DMA pages
@ 2019-12-04 21:36 John Hubbard
2019-12-04 21:36 ` [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
2019-12-04 21:36 ` [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
0 siblings, 2 replies; 6+ messages in thread
From: John Hubbard @ 2019-12-04 21:36 UTC (permalink / raw)
To: Andrew Morton, Jason Gunthorpe, Leon Romanovsky, Christoph Hellwig
Cc: Ira Weiny, linux-rdma, linux-mm, LKML, John Hubbard
Hi,
The reason I'm posting this is to request a review for patch 1. Once
everything seems OK, these two patches are going to be part of a larger
set (again, destined for linux-mm) that introduces FOLL_PIN and renames
some get_user_pages() cases to pin_user_pages(). I'm doing this a little
before -rc1, because it's a small and easy thing to get out of the way
early.
These are ultimately destined to go in via linux-mm (as opposed to
linux-rdma), in order to change some names in just one kernel release
cycle.
The first version of this patchset only had the IB/umem changes
(patch 2), and I also lacked a runtime Infiniband test, so
Leon Romanovsky reported a failure [1]. Patch 1 fixes that failure.
Since v1, I have (finally!) set up a basic two-node Infiniband system,
and as a result, I've reproduced the failure that Leon saw, via a
trivial run of "ib_write_bw", and confirmed that it's fixed in this
new patchset. Sorry it took me so long to do that; I am going to vaguely
blame "OFED" for the delay. :)
Entertaining IB side note: Jason: sure enough, as you mentioned, the
OFED installation did in fact hopelessly mangle my system. Once I went
back to a clean distro installation without all those OFED goodies,
everything Just Worked on the first try. Much simpler to understand,
too. ha.
This applies to today's linux.git: commit aedc0650f913 ("Merge tag
'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm").
[1] https://lore.kernel.org/r/20191124100724.GH136476@unreal
John Hubbard (2):
mm/gup: allow FOLL_FORCE for get_user_pages_fast()
IB/umem: use get_user_pages_fast() to pin DMA pages
drivers/infiniband/core/umem.c | 17 ++++++-----------
mm/gup.c | 3 ++-
2 files changed, 8 insertions(+), 12 deletions(-)
--
2.24.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast()
2019-12-04 21:36 [PATCH v2 0/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
@ 2019-12-04 21:36 ` John Hubbard
2019-12-09 18:25 ` Leon Romanovsky
2019-12-04 21:36 ` [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
1 sibling, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-12-04 21:36 UTC (permalink / raw)
To: Andrew Morton, Jason Gunthorpe, Leon Romanovsky, Christoph Hellwig
Cc: Ira Weiny, linux-rdma, linux-mm, LKML, John Hubbard, Christoph Hellwig
Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast().
This, combined with the fact that get_user_pages_fast() falls back to
"slow gup", which *does* accept FOLL_FORCE, leads to an odd situation:
if you need FOLL_FORCE, you cannot call get_user_pages_fast().
There does not appear to be any reason for filtering out FOLL_FORCE.
There is nothing in the _fast() implementation that requires that we
avoid writing to the pages. So it appears to have been an oversight.
Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
mm/gup.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c
index 7646bf993b25..5244b8090440 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2415,7 +2415,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned long addr, len, end;
int nr = 0, ret = 0;
- if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
+ if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
+ FOLL_FORCE)))
return -EINVAL;
start = untagged_addr(start) & PAGE_MASK;
--
2.24.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast()
2019-12-04 21:36 ` [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
@ 2019-12-09 18:25 ` Leon Romanovsky
2019-12-09 19:54 ` John Hubbard
0 siblings, 1 reply; 6+ messages in thread
From: Leon Romanovsky @ 2019-12-09 18:25 UTC (permalink / raw)
To: John Hubbard
Cc: Andrew Morton, Jason Gunthorpe, Christoph Hellwig, Ira Weiny,
linux-rdma, linux-mm, LKML, Christoph Hellwig
On Wed, Dec 04, 2019 at 01:36:02PM -0800, John Hubbard wrote:
> Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
> only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast().
> This, combined with the fact that get_user_pages_fast() falls back to
> "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation:
> if you need FOLL_FORCE, you cannot call get_user_pages_fast().
>
> There does not appear to be any reason for filtering out FOLL_FORCE.
> There is nothing in the _fast() implementation that requires that we
> avoid writing to the pages. So it appears to have been an oversight.
>
> Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
>
> Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> mm/gup.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
Thanks,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast()
2019-12-09 18:25 ` Leon Romanovsky
@ 2019-12-09 19:54 ` John Hubbard
0 siblings, 0 replies; 6+ messages in thread
From: John Hubbard @ 2019-12-09 19:54 UTC (permalink / raw)
To: Leon Romanovsky
Cc: Andrew Morton, Jason Gunthorpe, Christoph Hellwig, Ira Weiny,
linux-rdma, linux-mm, LKML, Christoph Hellwig
On 12/9/19 10:25 AM, Leon Romanovsky wrote:
> On Wed, Dec 04, 2019 at 01:36:02PM -0800, John Hubbard wrote:
>> Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
>> only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast().
>> This, combined with the fact that get_user_pages_fast() falls back to
>> "slow gup", which *does* accept FOLL_FORCE, leads to an odd situation:
>> if you need FOLL_FORCE, you cannot call get_user_pages_fast().
>>
>> There does not appear to be any reason for filtering out FOLL_FORCE.
>> There is nothing in the _fast() implementation that requires that we
>> avoid writing to the pages. So it appears to have been an oversight.
>>
>> Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().
>>
>> Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
>> Cc: Christoph Hellwig <hch@lst.de>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>> ---
>> mm/gup.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>
> Thanks,
> Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
>
Hi Leon, thanks for the reviews, great timing! I'll add the tags to
the commits, which I'm just about to post as part of the larger
"pin user pages" patchset.
thanks,
--
John Hubbard
NVIDIA
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages
2019-12-04 21:36 [PATCH v2 0/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-04 21:36 ` [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
@ 2019-12-04 21:36 ` John Hubbard
2019-12-09 18:25 ` Leon Romanovsky
1 sibling, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-12-04 21:36 UTC (permalink / raw)
To: Andrew Morton, Jason Gunthorpe, Leon Romanovsky, Christoph Hellwig
Cc: Ira Weiny, linux-rdma, linux-mm, LKML, John Hubbard,
Christoph Hellwig, Jan Kara, Jason Gunthorpe
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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.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 7a3b99597ead..214e87aa609d 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -266,16 +266,13 @@ 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;
@@ -283,8 +280,6 @@ 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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages
2019-12-04 21:36 ` [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
@ 2019-12-09 18:25 ` Leon Romanovsky
0 siblings, 0 replies; 6+ messages in thread
From: Leon Romanovsky @ 2019-12-09 18:25 UTC (permalink / raw)
To: John Hubbard
Cc: Andrew Morton, Jason Gunthorpe, Christoph Hellwig, Ira Weiny,
linux-rdma, linux-mm, LKML, Christoph Hellwig, Jan Kara,
Jason Gunthorpe
On Wed, Dec 04, 2019 at 01:36:03PM -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.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
> drivers/infiniband/core/umem.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
>
Thanks,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-12-04 21:36 [PATCH v2 0/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-04 21:36 ` [PATCH v2 1/2] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
2019-12-09 18:25 ` Leon Romanovsky
2019-12-09 19:54 ` John Hubbard
2019-12-04 21:36 ` [PATCH v2 2/2] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-09 18:25 ` Leon Romanovsky
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