Re: [PATCH 5/8] mm/gup: add FOLL_UNLOCK

[Mike Rapoport <rppt@kernel.org>]

On Fri, Jan 20, 2023 at 09:45:02AM -0400, Jason Gunthorpe wrote:
> On Thu, Jan 19, 2023 at 01:18:08PM +0200, Mike Rapoport wrote:
> > On Tue, Jan 17, 2023 at 11:58:36AM -0400, Jason Gunthorpe wrote:
> > > Setting FOLL_UNLOCK allows GUP to lock/unlock the mmap lock on its own. It
> > > is a more explicit replacement for locked != NULL. This clears the way for
> > > passing in locked = 1, without intending that the lock can be unlocked.
> > > 
> > > Set the flag in all cases where it is used, eg locked is present in the
> > > external interface or locked is used internally with locked = 0.
> > > 
> > > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> > > ---
> > >  include/linux/mm.h |  1 +
> > >  mm/gup.c           | 31 +++++++++++++++++++------------
> > >  2 files changed, 20 insertions(+), 12 deletions(-)
> > > 
> > > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > > index f3f196e4d66d6f..7496a5c8acede1 100644
> > > --- a/include/linux/mm.h
> > > +++ b/include/linux/mm.h
> > > @@ -3089,6 +3089,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
> > >  #define FOLL_FAST_ONLY	0x80000	/* gup_fast: prevent fall-back to slow gup */
> > >  #define FOLL_PCI_P2PDMA	0x100000 /* allow returning PCI P2PDMA pages */
> > >  #define FOLL_INTERRUPTIBLE  0x200000 /* allow interrupts from generic signals */
> > > +#define FOLL_UNLOCK	0x400000 /* allow unlocking the mmap lock */
> > 
> > Please add a comment that this is an internal flag.
> 
> #define FOLL_UNLOCK	0x400000 /* allow unlocking the mmap lock (internal only) */
> 
> OK?

Yep.

> Jason

-- 
Sincerely yours,
Mike.