linux-kernel - Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap

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Message-ID: <20200520124817.GG31189@ziepe.ca>
Date:   Wed, 20 May 2020 09:48:17 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Michel Lespinasse <walken@...gle.com>
Cc:     John Hubbard <jhubbard@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Liam Howlett <Liam.Howlett@...cle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>
Subject: Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock

On Tue, May 19, 2020 at 07:39:30PM -0700, Michel Lespinasse wrote:
> > > I think this assertion should be deleted from this driver.  It's there
> > > in case get_user_pages_fast() takes the mmap sem.  It would make sense to
> > > have this assertion in get_user_pages_fast() in case we take the fast path
> > > which doesn't acquire the mmap_sem.  Something like this:
> 
> I like this idea a lot - having might_lock assertions in
> get_user_pages_fast makes a log more sense than doing the same at the
> call sites.

+1 I've wanted to see more complete lockdep annotations in gup.c for a
while now.. There has been a number of bugs this would have caught

Jason