linux-kernel - Re: [PATCH v6 12/12] mmap locking API: convert mmap

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Date:   Fri, 22 May 2020 16:21:57 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Michel Lespinasse <walken@...gle.com>
Cc:     linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        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>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v6 12/12] mmap locking API: convert mmap_sem comments

On 5/21/20 7:25 PM, Andrew Morton wrote:
> On Thu, 21 May 2020 00:50:56 -0700 Michel Lespinasse <walken@...gle.com> wrote:
> 
>> > >   * Must be called holding task's alloc_lock to protect task's mems_allowed
>> > > - * and mempolicy.  May also be called holding the mmap_semaphore for write.
>> > > + * and mempolicy.  May also be called holding the mmap_lockaphore for write.
>> > >   */
>> > >  static int mpol_set_nodemask(struct mempolicy *pol,
>> > >                    const nodemask_t *nodes, struct nodemask_scratch *nsc)
>> >
>> > :)
>> 
>> Haha, good catch !
> 
> aww, you're all so cruel.  The world would be a better place if Linux
> had lockaphores!

Heh, in fact it does have them, but they are called "btrfs extent buffer locks",
see (or perhaps rather not) fs/btrfs/locking.c :)