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Message-ID: <907304d0599684b3caa6773197fd40e09191b48e.camel@linux.ibm.com>
Subject: Re: [PATCH v2 03/11] mm/gup: Applies counting method to monitor
 gup_pgd_range
From:   Leonardo Bras <leonardo@linux.ibm.com>
To:     John Hubbard <jhubbard@nvidia.com>, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, Linux-MM <linux-mm@kvack.org>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>,
        Thomas Gleixner <tglx@linutronix.de>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        YueHaibing <yuehaibing@huawei.com>,
        Keith Busch <keith.busch@intel.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
        Richard Fontana <rfontana@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Ganesh Goudar <ganeshgr@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Allison Randal <allison@lohutok.net>
Date:   Mon, 23 Sep 2019 18:01:54 -0300
In-Reply-To: <2e060677-eadf-c32e-d8c5-8e22c8ca118e@nvidia.com>
References: <20190920195047.7703-1-leonardo@linux.ibm.com>
         <20190920195047.7703-4-leonardo@linux.ibm.com>
         <2e060677-eadf-c32e-d8c5-8e22c8ca118e@nvidia.com>
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On Mon, 2019-09-23 at 13:27 -0700, John Hubbard wrote:
> I'd also like a second opinion from the "core" -mm maintainers, but it se=
ems like
> there is now too much code around the gup_pgd_range() call. Especially si=
nce there
> are two places where it's called--did you forget the other one in=20
> __get_user_pages_fast(), btw??
>=20
Oh, sorry, I missed this one. I will put it on v3.
(Also I will make sure to include linux-mm on v3.)

> Maybe the irq handling and atomic counting should be moved into start/fin=
ish
> calls, like this:
>=20
>      start_gup_fast_walk()
>      gup_pgd_range()
>      finish_gup_fast_walk()

There are cases where interrupt disable/enable is not done around the
lockless pagetable walk.
It may come from functions called above on stack, that's why I opted it
to be only the atomic operation.

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