Re: [PATCH 1/6] mm: khugepaged: fix radix tree node leak in shmem collapse error path

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jan Kara <jack@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 1/6] mm: khugepaged: fix radix tree node leak in shmem collapse error path
Date: Mon, 14 Nov 2016 22:40:54 +0300	[thread overview]
Message-ID: <20161114194054.GA12829@node.shutemov.name> (raw)
In-Reply-To: <20161114164822.GB5141@cmpxchg.org>

On Mon, Nov 14, 2016 at 11:48:22AM -0500, Johannes Weiner wrote:
> On Mon, Nov 14, 2016 at 10:52:50AM -0500, Johannes Weiner wrote:
> > On Mon, Nov 14, 2016 at 05:29:02PM +0300, Kirill A. Shutemov wrote:
> > > @@ -1400,7 +1400,9 @@ static void collapse_shmem(struct mm_struct *mm,
> > >  					PAGE_SIZE, 0);
> > >  
> > >  		spin_lock_irq(&mapping->tree_lock);
> > > -
> > > +		slot = radix_tree_lookup_slot(&mapping->page_tree, index);
> > > +		VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
> > > +					&mapping->tree_lock), page);
> > >  		VM_BUG_ON_PAGE(page_mapped(page), page);
> > 
> > That looks good to me. The slot may get relocated, but the content
> > shouldn't change with the page locked.
> > 
> > Are you going to send a full patch with changelog and sign-off? If so,
> > please add:
> > 
> > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> 
> Just to clarify, this is in addition to my radix_tree_iter_next()
> change. The iterator still needs to be reloaded because the number of
> valid slots that come after the current one can change as well.

Could you just amend all these fixups into your patch?

-- 
 Kirill A. Shutemov