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Subject: Re: [PATCH v6 12/12] mmap locking API: convert mmap_sem comments
To:     Andrew Morton <akpm@linux-foundation.org>,
        Michel Lespinasse <walken@google.com>
Cc:     linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Matthew Wilcox <willy@infradead.org>,
        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>,
        John Hubbard <jhubbard@nvidia.com>
References: <20200520052908.204642-1-walken@google.com>
 <20200520052908.204642-13-walken@google.com>
 <e01060e9-6f00-7fa8-5da0-c9250c951d10@suse.cz>
 <CANN689GXWS9yHTw0aN-tAkd9tyA-vRn0GbJgC+Td=1r13KBZzA@mail.gmail.com>
 <20200521102516.01dbc9fcc539baba96224c3f@linux-foundation.org>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <9858cd98-b303-beb4-82f6-52f902f98772@suse.cz>
Date:   Fri, 22 May 2020 16:21:57 +0200
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On 5/21/20 7:25 PM, Andrew Morton wrote:
> On Thu, 21 May 2020 00:50:56 -0700 Michel Lespinasse <walken@google.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 :)