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Date:   Tue, 19 May 2020 06:10:09 -0700
From:   Michel Lespinasse <walken@google.com>
To:     Laurent Dufour <ldufour@linux.ibm.com>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Liam Howlett <Liam.Howlett@oracle.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Daniel Jordan <daniel.m.jordan@oracle.com>
Subject: Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock
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On Mon, May 18, 2020 at 03:45:22PM +0200, Laurent Dufour wrote:
> Le 24/04/2020 ? 03:39, Michel Lespinasse a ?crit?:
> > Rename the mmap_sem field to mmap_lock. Any new uses of this lock
> > should now go through the new mmap locking api. The mmap_lock is
> > still implemented as a rwsem, though this could change in the future.
> > 
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > index dc9ef302f517..701f3995f621 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > @@ -661,7 +661,7 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
> >   	struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr;
> >   	int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
> > -	might_lock_read(&current->mm->mmap_sem);
> > +	might_lock_read(&current->mm->mmap_lock);
> 
> Why not a mm_might_lock_read() new API to hide the mmap_lock, and add it to
> the previous patch?

I'm not sure why this is needed - we may rework the lock to be
something else than rwsem, but might_lock_read should still apply to
it and make sense ? I'm not sure what the extra API would bring...

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.