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Date:   Mon, 4 Nov 2019 16:57:38 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     John Hubbard <jhubbard@nvidia.com>
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Subject: Re: [PATCH v2 07/18] infiniband: set FOLL_PIN, FOLL_LONGTERM via
 pin_longterm_pages*()
Message-ID: <20191104205738.GH30938@ziepe.ca>
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On Mon, Nov 04, 2019 at 12:48:13PM -0800, John Hubbard wrote:
> On 11/4/19 12:33 PM, Jason Gunthorpe wrote:
> ...
> >> diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
> >> index 24244a2f68cc..c5a78d3e674b 100644
> >> +++ b/drivers/infiniband/core/umem.c
> >> @@ -272,11 +272,10 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
> >>  
> >>  	while (npages) {
> >>  		down_read(&mm->mmap_sem);
> >> -		ret = get_user_pages(cur_base,
> >> +		ret = pin_longterm_pages(cur_base,
> >>  				     min_t(unsigned long, npages,
> >>  					   PAGE_SIZE / sizeof (struct page *)),
> >> -				     gup_flags | FOLL_LONGTERM,
> >> -				     page_list, NULL);
> >> +				     gup_flags, page_list, NULL);
> > 
> > FWIW, this one should be converted to fast as well, I think we finally
> > got rid of all the blockers for that?
> > 
> 
> I'm not aware of any blockers on the gup.c end, anyway. The only broken thing we
> have there is "gup remote + FOLL_LONGTERM". But we can do "gup fast + LONGTERM". 

I mean the use of the mmap_sem here is finally in a way where we can
just delete the mmap_sem and use _fast
 
ie, AFAIK there is no need for the mmap_sem to be held during
ib_umem_add_sg_table()

This should probably be a standalone patch however

Jason