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From:   Michel Lespinasse <walken@google.com>
Date:   Mon, 20 Apr 2020 17:51:47 -0700
Message-ID: <CANN689Eu72s1FTCfgXp8NZJ80jj9-pUNdj6gw4OKZPa1pR5+jg@mail.gmail.com>
Subject: Re: [PATCH v4 06/10] mmap locking API: convert nested write lock sites
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        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>
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On Mon, Apr 20, 2020 at 12:33 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Apr 14, 2020 at 05:43:49PM -0700, Michel Lespinasse wrote:
> > @@ -47,7 +48,7 @@ static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
> >        * when the new ->mm is used for the first time.
> >        */
> >       __switch_mm(&new->context.id);
> > -     down_write_nested(&new->mmap_sem, 1);
> > +     mmap_write_lock_nested(new, 1);
>
> This should have already been using SINGLE_DEPTH_NESTING.  1 is
> uninformative.

Sure, I can change that.
Note, all mmap_write_lock_nested call sites use single depth nesting,
so I'm not entirely sure if the argument should be passed to
mmap_write_lock_nested in the first place ?

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