linux-kernel - Re: [PATCH] IB/mthca: Fix how mthca_map_user

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Date:   Fri, 26 Jan 2018 10:44:28 -0500
From:   Doug Ledford <dledford@...hat.com>
To:     Davidlohr Bueso <dave@...olabs.net>, Jason Gunthorpe <jgg@...pe.ca>
Cc:     roland@...estorage.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] IB/mthca: Fix how mthca_map_user_db() calls gup

On Thu, 2018-01-25 at 11:27 -0800, Davidlohr Bueso wrote:
> On Thu, 25 Jan 2018, Jason Gunthorpe wrote:
> 
> > > 
> > > Since the original post was referred to an ABBA deadlock, wouldn't we
> > > have to drop db_tab->mutex, then grab both in the proper order?
> > 
> > I had understood that was only a concern because Davidlohr was having
> > trouble proving the callchain didn't include mmap_sem already..
> > 
> > I can see the call chain all ends on verbs ops, and I know verbs ops
> > with ucontext's are never called under mmap_sem by the core code..
> 
> Right. Ok so this simplifies things and we can just use gup_fast().
> 
> Thanks,
> Davidlohr

Thanks, applied.

-- 
Doug Ledford <dledford@...hat.com>
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