linux-ext4 - Re: [RFC PATCH v2 15/19] mm/gup: Introduce vaddr_pin

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Date:   Mon, 12 Aug 2019 14:01:17 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Theodore Ts'o <tytso@....edu>, Michal Hocko <mhocko@...e.com>,
        Dave Chinner <david@...morbit.com>, linux-xfs@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-ext4@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v2 15/19] mm/gup: Introduce vaddr_pin_pages()

On Sun, Aug 11, 2019 at 04:07:23PM -0700, John Hubbard wrote:
> On 8/9/19 3:58 PM, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > The addition of FOLL_LONGTERM has taken on additional meaning for CMA
> > pages.
> > 
> > In addition subsystems such as RDMA require new information to be passed
> > to the GUP interface to track file owning information.  As such a simple
> > FOLL_LONGTERM flag is no longer sufficient for these users to pin pages.
> > 
> > Introduce a new GUP like call which takes the newly introduced vaddr_pin
> > information.  Failure to pass the vaddr_pin object back to a vaddr_put*
> > call will result in a failure if pins were created on files during the
> > pin operation.
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > 
> 
> I'm creating a new call site conversion series, to replace the 
> "put_user_pages(): miscellaneous call sites" series. This uses
> vaddr_pin_pages*() where appropriate. So it's based on your series here.
> 
> btw, while doing that, I noticed one more typo while re-reading some of the comments. 
> Thought you probably want to collect them all for the next spin. Below...
> 
> > ---
> > Changes from list:
> > 	Change to vaddr_put_pages_dirty_lock
> > 	Change to vaddr_unpin_pages_dirty_lock
> > 
> >  include/linux/mm.h |  5 ++++
> >  mm/gup.c           | 59 ++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 64 insertions(+)
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 657c947bda49..90c5802866df 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1603,6 +1603,11 @@ int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc);
> >  int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
> >  			struct task_struct *task, bool bypass_rlim);
> >  
> > +long vaddr_pin_pages(unsigned long addr, unsigned long nr_pages,
> > +		     unsigned int gup_flags, struct page **pages,
> > +		     struct vaddr_pin *vaddr_pin);
> > +void vaddr_unpin_pages_dirty_lock(struct page **pages, unsigned long nr_pages,
> > +				  struct vaddr_pin *vaddr_pin, bool make_dirty);
> >  bool mapping_inode_has_layout(struct vaddr_pin *vaddr_pin, struct page *page);
> >  
> >  /* Container for pinned pfns / pages */
> > diff --git a/mm/gup.c b/mm/gup.c
> > index eeaa0ddd08a6..6d23f70d7847 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -2536,3 +2536,62 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(get_user_pages_fast);
> > +
> > +/**
> > + * vaddr_pin_pages pin pages by virtual address and return the pages to the
> > + * user.
> > + *
> > + * @addr, start address
> > + * @nr_pages, number of pages to pin
> > + * @gup_flags, flags to use for the pin
> > + * @pages, array of pages returned
> > + * @vaddr_pin, initalized meta information this pin is to be associated
> 
> Typo:
>                   initialized

Thanks fixed.
Ira

> 
> 
> thanks,
> -- 
> John Hubbard
> NVIDIA