linux-kernel - Re: [PATCH v3 07/10] mmap locking API: add mmap_read_release() and mmap_read_unlock_non

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Date:   Mon, 6 Apr 2020 08:39:53 -0700
From:   Michel Lespinasse <walken@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        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>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Markus Elfring <Markus.Elfring@....de>
Subject: Re: [PATCH v3 07/10] mmap locking API: add mmap_read_release() and mmap_read_unlock_non_owner()

On Wed, Apr 1, 2020 at 6:46 AM Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Mar 27, 2020 at 03:50:59PM -0700, Michel Lespinasse wrote:
> > Add a couple APIs to allow splitting mmap_read_unlock() into two calls:
> > - mmap_read_release(), called by the task that had taken the mmap lock;
> > - mmap_read_unlock_non_owner(), called from a work queue.
> >
> > These apis are used by kernel/bpf/stackmap.c only.
>
> That code is an absolute abomination and should never have gotten
> merged.

I have to say, it's causing me some grief too :/

> That said; I would prefer a mmap_read_trylock_nonowner() over
> mmap_read_release() existing.

It only addresses part of the issue, but I suppose I could do that. Is
this something I could append to the end of this series, or do I need
to prepare a v4 for such changes ?