From: John Hubbard <jhubbard@nvidia.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
"Björn Töpel" <bjorn.topel@intel.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Dave Chinner" <david@fromorbit.com>,
"David Airlie" <airlied@linux.ie>,
"David S . Miller" <davem@davemloft.net>,
"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
"Jason Gunthorpe" <jgg@ziepe.ca>, "Jens Axboe" <axboe@kernel.dk>,
"Jonathan Corbet" <corbet@lwn.net>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
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"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>,
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LKML <linux-kernel@vger.kernel.org>,
"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH v11 04/25] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages
Date: Wed, 18 Dec 2019 16:32:28 -0800 [thread overview]
Message-ID: <ddd08105-f48a-dbe1-7de1-f2fa2c5772a9@nvidia.com> (raw)
In-Reply-To: <20191218160420.gyt4c45e6zsnxqv6@box>
On 12/18/19 8:04 AM, Kirill A. Shutemov wrote:
> On Mon, Dec 16, 2019 at 02:25:16PM -0800, John Hubbard wrote:
>> An upcoming patch changes and complicates the refcounting and
>> especially the "put page" aspects of it. In order to keep
>> everything clean, refactor the devmap page release routines:
>>
>> * Rename put_devmap_managed_page() to page_is_devmap_managed(),
>> and limit the functionality to "read only": return a bool,
>> with no side effects.
>>
>> * Add a new routine, put_devmap_managed_page(), to handle checking
>> what kind of page it is, and what kind of refcount handling it
>> requires.
>>
>> * Rename __put_devmap_managed_page() to free_devmap_managed_page(),
>> and limit the functionality to unconditionally freeing a devmap
>> page.
>
> What the reason to separate put_devmap_managed_page() from
> free_devmap_managed_page() if free_devmap_managed_page() has exacly one
> caller? Is it preparation for the next patches?
Yes. A later patch, #23, adds another caller: __unpin_devmap_managed_user_page().
...
>> @@ -971,7 +971,14 @@ static inline bool put_devmap_managed_page(struct page *page)
>> return false;
>> }
>>
>> +bool put_devmap_managed_page(struct page *page);
>> +
>> #else /* CONFIG_DEV_PAGEMAP_OPS */
>> +static inline bool page_is_devmap_managed(struct page *page)
>> +{
>> + return false;
>> +}
>> +
>> static inline bool put_devmap_managed_page(struct page *page)
>> {
>> return false;
>> @@ -1028,8 +1035,10 @@ static inline void put_page(struct page *page)
>> * need to inform the device driver through callback. See
>> * include/linux/memremap.h and HMM for details.
>> */
>> - if (put_devmap_managed_page(page))
>> + if (page_is_devmap_managed(page)) {
>> + put_devmap_managed_page(page);
>
> put_devmap_managed_page() has yet another page_is_devmap_managed() check
> inside. It looks strange.
>
Good point, it's an extra unnecessary check. So to clean it up, I'll note
that the "if" check is required here in put_page(), in order to stay out of
non-inlined function calls in the hot path (put_page()). So I'll do the
following:
* Leave the above code as it is here
* Simplify put_devmap_managed_page(), it was trying to do two separate things,
and those two things have different requirements. So change it to a void
function, with a WARN_ON_ONCE to assert that page_is_devmap_managed() is true,
* And change the other caller (release_pages()) to do that check.
...
>> @@ -1102,3 +1102,27 @@ void __init swap_setup(void)
>> * _really_ don't want to cluster much more
>> */
>> }
>> +
>> +#ifdef CONFIG_DEV_PAGEMAP_OPS
>> +bool put_devmap_managed_page(struct page *page)
>> +{
>> + bool is_devmap = page_is_devmap_managed(page);
>> +
>> + if (is_devmap) {
>
> Reversing the condition would save you an indentation level.
Yes. Done.
I'll also git-reply with an updated patch so you can see what it looks like.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-12-19 0:35 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-16 22:25 [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN John Hubbard
2019-12-16 22:25 ` [PATCH v11 01/25] mm/gup: factor out duplicate code from four routines John Hubbard
2019-12-18 15:52 ` Kirill A. Shutemov
2019-12-18 22:15 ` John Hubbard
2019-12-18 22:45 ` Kirill A. Shutemov
2019-12-16 22:25 ` [PATCH v11 02/25] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-12-16 22:25 ` [PATCH v11 03/25] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-12-16 22:25 ` [PATCH v11 04/25] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages John Hubbard
2019-12-18 16:04 ` Kirill A. Shutemov
2019-12-19 0:32 ` John Hubbard [this message]
2019-12-19 0:40 ` [PATCH v12] " John Hubbard
2019-12-19 5:27 ` [PATCH v11 04/25] " Dan Williams
2019-12-19 5:48 ` John Hubbard
2019-12-19 6:52 ` Dan Williams
2019-12-19 7:33 ` John Hubbard
2019-12-16 22:25 ` [PATCH v11 05/25] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-12-16 22:25 ` [PATCH v11 06/25] mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM John Hubbard
2019-12-18 16:19 ` Kirill A. Shutemov
2019-12-18 22:15 ` John Hubbard
2019-12-16 22:25 ` [PATCH v11 07/25] vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call John Hubbard
2019-12-16 22:25 ` [PATCH v11 08/25] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
2019-12-16 22:25 ` [PATCH v11 09/25] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-16 22:25 ` [PATCH v11 10/25] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-12-16 22:25 ` [PATCH v11 11/25] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-16 22:25 ` [PATCH v11 12/25] IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-12-16 22:25 ` [PATCH v11 13/25] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-12-16 22:25 ` [PATCH v11 14/25] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-12-16 22:25 ` [PATCH v11 15/25] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-12-16 22:25 ` [PATCH v11 16/25] net/xdp: " John Hubbard
2019-12-16 22:25 ` [PATCH v11 17/25] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-12-16 22:25 ` [PATCH v11 18/25] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-12-16 22:25 ` [PATCH v11 19/25] vfio, mm: " John Hubbard
2019-12-16 22:25 ` [PATCH v11 20/25] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-16 22:25 ` [PATCH v11 21/25] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-12-16 22:25 ` [PATCH v11 22/25] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard
2019-12-16 22:25 ` [PATCH v11 23/25] mm/gup: track FOLL_PIN pages John Hubbard
2019-12-17 14:19 ` [PATCH v12 " John Hubbard
2019-12-16 22:25 ` [PATCH v11 24/25] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-12-16 22:25 ` [PATCH v11 25/25] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-12-17 7:39 ` [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN Jan Kara
2019-12-19 13:26 ` Leon Romanovsky
2019-12-19 20:30 ` John Hubbard
2019-12-19 21:07 ` Jason Gunthorpe
2019-12-19 21:13 ` John Hubbard
2019-12-20 13:34 ` Jason Gunthorpe
2019-12-21 0:32 ` Dan Williams
2019-12-23 18:24 ` Jason Gunthorpe
2019-12-19 22:58 ` John Hubbard
2019-12-20 18:48 ` Leon Romanovsky
2019-12-20 23:13 ` John Hubbard
2019-12-20 18:29 ` Leon Romanovsky
2019-12-20 23:54 ` John Hubbard
2019-12-21 10:08 ` Leon Romanovsky
2019-12-21 23:59 ` John Hubbard
2019-12-22 13:23 ` Leon Romanovsky
2019-12-25 2:03 ` John Hubbard
2019-12-25 5:26 ` Leon Romanovsky
2019-12-27 21:56 ` John Hubbard
2019-12-29 4:33 ` John Hubbard
2020-01-06 9:01 ` Jan Kara
2020-01-07 1:26 ` John Hubbard
2019-12-20 9:21 ` Jan Kara
2019-12-21 0:02 ` John Hubbard
2019-12-21 0:33 ` Dan Williams
2019-12-21 0:41 ` John Hubbard
2019-12-21 0:51 ` Dan Williams
2019-12-21 0:53 ` John Hubbard
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