linux-kernel - Re: [PATCH 2/3] pagewalk: separate function pointers from iterator data

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Message-ID: <20190829065959.GA11628@lst.de>
Date:   Thu, 29 Aug 2019 08:59:59 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jason Gunthorpe <jgg@...lanox.com>
Cc:     Christoph Hellwig <hch@....de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Hellström <thomas@...pmail.org>,
        Jerome Glisse <jglisse@...hat.com>,
        Steven Price <steven.price@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Hellstrom <thellstrom@...are.com>
Subject: Re: [PATCH 2/3] pagewalk: separate function pointers from iterator
 data

On Wed, Aug 28, 2019 at 03:05:19PM +0000, Jason Gunthorpe wrote:
> > @@ -1217,7 +1222,8 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
> >  						0, NULL, mm, 0, -1UL);
> >  			mmu_notifier_invalidate_range_start(&range);
> >  		}
> > -		walk_page_range(0, mm->highest_vm_end, &clear_refs_walk);
> > +		walk_page_range(mm, 0, mm->highest_vm_end, &clear_refs_walk_ops,
> > +				&cp);
> 
> Is the difference between TASK_SIZE and 'highest_vm_end' deliberate,
> or should we add a 'walk_all_pages'() mini helper for this? I see most
> of the users are using one or the other variant.

I have no idea to be honest.  A walk_all_pages-like helper doesn't
seem like a bad idea, but the priority seems lower than cleaning up
all the callers using walk_page_range on a vma..