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From: John Hubbard <jhubbard@nvidia.com>
To: Mike Rapoport <rppt@linux.ibm.com>, <john.hubbard@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
	Jan Kara <jack@suse.cz>, Tom Talpey <tom@talpey.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christian Benvenuti <benve@cisco.com>,
	Christoph Hellwig <hch@infradead.org>,
	Christopher Lameter <cl@linux.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dennis Dalessandro <dennis.dalessandro@intel.com>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Jerome Glisse <jglisse@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Michal Hocko <mhocko@kernel.org>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	Ralph Campbell <rcampbell@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions
Date: Tue, 4 Dec 2018 17:40:59 -0800
Message-ID: <a34aca95-7372-4fd2-b72a-004731fc10ed@nvidia.com> (raw)
In-Reply-To: <20181204075323.GI26700@rapoport-lnx>

On 12/3/18 11:53 PM, Mike Rapoport wrote:
> Hi John,
> 
> Thanks for having documentation as a part of the patch. Some kernel-doc
> nits below.
> 
> On Mon, Dec 03, 2018 at 04:17:19PM -0800, john.hubbard@gmail.com wrote:
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> Introduces put_user_page(), which simply calls put_page().
>> This provides a way to update all get_user_pages*() callers,
>> so that they call put_user_page(), instead of put_page().
>>
>> Also introduces put_user_pages(), and a few dirty/locked variations,
>> as a replacement for release_pages(), and also as a replacement
>> for open-coded loops that release multiple pages.
>> These may be used for subsequent performance improvements,
>> via batching of pages to be released.
>>
>> This is the first step of fixing the problem described in [1]. The steps
>> are:
>>
>> 1) (This patch): provide put_user_page*() routines, intended to be used
>>    for releasing pages that were pinned via get_user_pages*().
>>
>> 2) Convert all of the call sites for get_user_pages*(), to
>>    invoke put_user_page*(), instead of put_page(). This involves dozens of
>>    call sites, and will take some time.
>>
>> 3) After (2) is complete, use get_user_pages*() and put_user_page*() to
>>    implement tracking of these pages. This tracking will be separate from
>>    the existing struct page refcounting.
>>
>> 4) Use the tracking and identification of these pages, to implement
>>    special handling (especially in writeback paths) when the pages are
>>    backed by a filesystem. Again, [1] provides details as to why that is
>>    desirable.
>>
>> [1] https://lwn.net/Articles/753027/ : "The Trouble with get_user_pages()"
>>
>> Reviewed-by: Jan Kara <jack@suse.cz>
>>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Christopher Lameter <cl@linux.com>
>> Cc: Jason Gunthorpe <jgg@ziepe.ca>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Jan Kara <jack@suse.cz>
>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>> Cc: Jerome Glisse <jglisse@redhat.com>
>> Cc: Christoph Hellwig <hch@infradead.org>
>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>> ---
>>  include/linux/mm.h | 20 ++++++++++++
>>  mm/swap.c          | 80 ++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 100 insertions(+)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 5411de93a363..09fbb2c81aba 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -963,6 +963,26 @@ static inline void put_page(struct page *page)
>>  		__put_page(page);
>>  }
>>
>> +/*
>> + * put_user_page() - release a page that had previously been acquired via
>> + * a call to one of the get_user_pages*() functions.
> 
> Please add @page parameter description, otherwise kernel-doc is unhappy

Hi Mike,

Sorry I missed these kerneldoc points from your earlier review! I'll fix it
up now and it will show up in the next posting.

> 
>> + *
>> + * Pages that were pinned via get_user_pages*() must be released via
>> + * either put_user_page(), or one of the put_user_pages*() routines
>> + * below. This is so that eventually, pages that are pinned via
>> + * get_user_pages*() can be separately tracked and uniquely handled. In
>> + * particular, interactions with RDMA and filesystems need special
>> + * handling.
>> + */
>> +static inline void put_user_page(struct page *page)
>> +{
>> +	put_page(page);
>> +}
>> +
>> +void put_user_pages_dirty(struct page **pages, unsigned long npages);
>> +void put_user_pages_dirty_lock(struct page **pages, unsigned long npages);
>> +void put_user_pages(struct page **pages, unsigned long npages);
>> +
>>  #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
>>  #define SECTION_IN_PAGE_FLAGS
>>  #endif
>> diff --git a/mm/swap.c b/mm/swap.c
>> index aa483719922e..bb8c32595e5f 100644
>> --- a/mm/swap.c
>> +++ b/mm/swap.c
>> @@ -133,6 +133,86 @@ void put_pages_list(struct list_head *pages)
>>  }
>>  EXPORT_SYMBOL(put_pages_list);
>>
>> +typedef int (*set_dirty_func)(struct page *page);
>> +
>> +static void __put_user_pages_dirty(struct page **pages,
>> +				   unsigned long npages,
>> +				   set_dirty_func sdf)
>> +{
>> +	unsigned long index;
>> +
>> +	for (index = 0; index < npages; index++) {
>> +		struct page *page = compound_head(pages[index]);
>> +
>> +		if (!PageDirty(page))
>> +			sdf(page);
>> +
>> +		put_user_page(page);
>> +	}
>> +}
>> +
>> +/*
>> + * put_user_pages_dirty() - for each page in the @pages array, make
>> + * that page (or its head page, if a compound page) dirty, if it was
>> + * previously listed as clean. Then, release the page using
>> + * put_user_page().
>> + *
>> + * Please see the put_user_page() documentation for details.
>> + *
>> + * set_page_dirty(), which does not lock the page, is used here.
>> + * Therefore, it is the caller's responsibility to ensure that this is
>> + * safe. If not, then put_user_pages_dirty_lock() should be called instead.
>> + *
>> + * @pages:  array of pages to be marked dirty and released.
>> + * @npages: number of pages in the @pages array.
> 
> Please put the parameters description next to the brief function
> description, as described in [1]
> 
> [1] https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation
> 

OK. 

> 
>> + *
>> + */
>> +void put_user_pages_dirty(struct page **pages, unsigned long npages)
>> +{
>> +	__put_user_pages_dirty(pages, npages, set_page_dirty);
>> +}
>> +EXPORT_SYMBOL(put_user_pages_dirty);
>> +
>> +/*
>> + * put_user_pages_dirty_lock() - for each page in the @pages array, make
>> + * that page (or its head page, if a compound page) dirty, if it was
>> + * previously listed as clean. Then, release the page using
>> + * put_user_page().
>> + *
>> + * Please see the put_user_page() documentation for details.
>> + *
>> + * This is just like put_user_pages_dirty(), except that it invokes
>> + * set_page_dirty_lock(), instead of set_page_dirty().
>> + *
>> + * @pages:  array of pages to be marked dirty and released.
>> + * @npages: number of pages in the @pages array.
> 
> Ditto

OK.

> 
>> + *
>> + */
>> +void put_user_pages_dirty_lock(struct page **pages, unsigned long npages)
>> +{
>> +	__put_user_pages_dirty(pages, npages, set_page_dirty_lock);
>> +}
>> +EXPORT_SYMBOL(put_user_pages_dirty_lock);
>> +
>> +/*
>> + * put_user_pages() - for each page in the @pages array, release the page
>> + * using put_user_page().
>> + *
>> + * Please see the put_user_page() documentation for details.
>> + *
>> + * @pages:  array of pages to be marked dirty and released.
>> + * @npages: number of pages in the @pages array.
>> + *
> 
> And here as well :)

OK.


thanks,
-- 
John Hubbard
NVIDIA
 

  reply index

Thread overview: 213+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-04  0:17 [PATCH 0/2] put_user_page*(): start converting the call sites john.hubbard
2018-12-04  0:17 ` [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions john.hubbard
2018-12-04  7:53   ` Mike Rapoport
2018-12-05  1:40     ` John Hubbard [this message]
2018-12-04 20:28   ` Dan Williams
2018-12-04 21:56     ` John Hubbard
2018-12-04 23:03       ` Dan Williams
2018-12-05  0:36         ` Jerome Glisse
2018-12-05  0:40           ` Dan Williams
2018-12-05  0:59             ` John Hubbard
2018-12-05  0:58         ` John Hubbard
2018-12-05  1:00           ` Dan Williams
2018-12-05  1:15           ` Matthew Wilcox
2018-12-05  1:44             ` Jerome Glisse
2018-12-05  1:57               ` John Hubbard
2018-12-07  2:45                 ` John Hubbard
2018-12-07 19:16                   ` Jerome Glisse
2018-12-07 19:26                     ` Dan Williams
2018-12-07 19:40                       ` Jerome Glisse
2018-12-08  0:52                     ` John Hubbard
2018-12-08  2:24                       ` Jerome Glisse
2018-12-10 10:28                         ` Jan Kara
2018-12-12 15:03                           ` Jerome Glisse
2018-12-12 16:27                             ` Dan Williams
2018-12-12 17:02                               ` Jerome Glisse
2018-12-12 17:49                                 ` Dan Williams
2018-12-12 19:07                                   ` John Hubbard
2018-12-12 21:30                               ` Jerome Glisse
2018-12-12 21:40                                 ` Dan Williams
2018-12-12 21:53                                   ` Jerome Glisse
2018-12-12 22:11                                     ` Matthew Wilcox
2018-12-12 22:16                                       ` Jerome Glisse
2018-12-12 23:37                                     ` Jason Gunthorpe
2018-12-12 23:46                                       ` John Hubbard
2018-12-12 23:54                                       ` Dan Williams
2018-12-13  0:01                                       ` Jerome Glisse
2018-12-13  0:18                                         ` Dan Williams
2018-12-13  0:44                                           ` Jerome Glisse
2018-12-13  3:26                                             ` Jason Gunthorpe
2018-12-13  3:20                                         ` Jason Gunthorpe
2018-12-13 12:43                                           ` Jerome Glisse
2018-12-13 13:40                                             ` Tom Talpey
2018-12-13 14:18                                               ` Jerome Glisse
2018-12-13 14:51                                                 ` Tom Talpey
2018-12-13 15:18                                                   ` Jerome Glisse
2018-12-13 18:12                                                     ` Tom Talpey
2018-12-13 19:18                                                       ` Jerome Glisse
2018-12-14 10:41                                             ` Jan Kara
2018-12-14 15:25                                               ` Jerome Glisse
2018-12-12 21:56                                 ` John Hubbard
2018-12-12 22:04                                   ` Jerome Glisse
2018-12-12 22:11                                     ` John Hubbard
2018-12-12 22:14                                       ` Jerome Glisse
2018-12-12 22:17                                         ` John Hubbard
2018-12-12 21:46                             ` Dave Chinner
2018-12-12 21:59                               ` Jerome Glisse
2018-12-13  0:51                                 ` Dave Chinner
2018-12-13  2:02                                   ` Jerome Glisse
2018-12-13 15:56                                     ` Christopher Lameter
2018-12-13 16:02                                       ` Jerome Glisse
2018-12-14  6:00                                     ` Dave Chinner
2018-12-14 15:13                                       ` Jerome Glisse
2018-12-14  3:52                                   ` John Hubbard
2018-12-14  5:21                                     ` Dan Williams
2018-12-14  6:11                                       ` John Hubbard
2018-12-14 15:20                                         ` Jerome Glisse
2018-12-14 19:38                                         ` Dan Williams
2018-12-14 19:48                                           ` Matthew Wilcox
2018-12-14 19:53                                             ` Dave Hansen
2018-12-14 20:03                                               ` Matthew Wilcox
2018-12-14 20:17                                                 ` Dan Williams
2018-12-14 20:29                                                   ` Matthew Wilcox
2018-12-15  0:41                                                 ` John Hubbard
2018-12-17  8:56                                           ` Jan Kara
2018-12-17 18:28                                             ` Dan Williams
2018-12-14 15:43                               ` Jan Kara
2018-12-16 21:58                                 ` Dave Chinner
2018-12-17 18:11                                   ` Jerome Glisse
2018-12-17 18:34                                     ` Matthew Wilcox
2018-12-17 19:48                                       ` Jerome Glisse
2018-12-17 19:51                                         ` Matthew Wilcox
2018-12-17 19:54                                           ` Jerome Glisse
2018-12-17 19:59                                             ` Matthew Wilcox
2018-12-17 20:55                                               ` Jerome Glisse
2018-12-17 21:03                                                 ` Matthew Wilcox
2018-12-17 21:15                                                   ` Jerome Glisse
2018-12-18  1:09                                       ` Dave Chinner
2018-12-18  6:12                                       ` Darrick J. Wong
2018-12-18  9:30                                       ` Jan Kara
2018-12-18 23:29                                         ` John Hubbard
2018-12-19  2:07                                           ` Jerome Glisse
2018-12-19 11:08                                             ` Jan Kara
2018-12-20 10:54                                               ` John Hubbard
2018-12-20 16:50                                                 ` Jerome Glisse
2018-12-20 16:57                                                   ` Dan Williams
2018-12-20 16:49                                               ` Jerome Glisse
2019-01-03  1:55                                               ` Jerome Glisse
2019-01-03  3:27                                                 ` John Hubbard
2019-01-03 14:57                                                   ` Jerome Glisse
2019-01-03  9:26                                                 ` Jan Kara
2019-01-03 14:44                                                   ` Jerome Glisse
2019-01-11  2:59                                                     ` John Hubbard
2019-01-11  2:59                                                       ` John Hubbard
2019-01-11 16:51                                                       ` Jerome Glisse
2019-01-11 16:51                                                         ` Jerome Glisse
2019-01-12  1:04                                                         ` John Hubbard
2019-01-12  1:04                                                           ` John Hubbard
2019-01-12  2:02                                                           ` Jerome Glisse
2019-01-12  2:02                                                             ` Jerome Glisse
2019-01-12  2:38                                                             ` John Hubbard
2019-01-12  2:38                                                               ` John Hubbard
2019-01-12  2:46                                                               ` Jerome Glisse
2019-01-12  2:46                                                                 ` Jerome Glisse
2019-01-12  3:06                                                                 ` John Hubbard
2019-01-12  3:06                                                                   ` John Hubbard
2019-01-12  3:25                                                                   ` Jerome Glisse
2019-01-12  3:25                                                                     ` Jerome Glisse
2019-01-12 20:46                                                                     ` John Hubbard
2019-01-12 20:46                                                                       ` John Hubbard
2019-01-14 14:54                                                                   ` Jan Kara
2019-01-14 14:54                                                                     ` Jan Kara
2019-01-14 17:21                                                                     ` Jerome Glisse
2019-01-14 17:21                                                                       ` Jerome Glisse
2019-01-14 19:09                                                                       ` John Hubbard
2019-01-14 19:09                                                                         ` John Hubbard
2019-01-15  8:34                                                                         ` Jan Kara
2019-01-15  8:34                                                                           ` Jan Kara
2019-01-15 21:39                                                                           ` John Hubbard
2019-01-15 21:39                                                                             ` John Hubbard
2019-01-15  8:07                                                                       ` Jan Kara
2019-01-15  8:07                                                                         ` Jan Kara
2019-01-15 17:15                                                                         ` Jerome Glisse
2019-01-15 17:15                                                                           ` Jerome Glisse
2019-01-15 21:56                                                                           ` John Hubbard
2019-01-15 21:56                                                                             ` John Hubbard
2019-01-15 22:12                                                                             ` Jerome Glisse
2019-01-15 22:12                                                                               ` Jerome Glisse
2019-01-16  0:44                                                                               ` John Hubbard
2019-01-16  0:44                                                                                 ` John Hubbard
2019-01-16  1:56                                                                                 ` Jerome Glisse
2019-01-16  1:56                                                                                   ` Jerome Glisse
2019-01-16  2:01                                                                                   ` Dan Williams
2019-01-16  2:01                                                                                     ` Dan Williams
2019-01-16  2:23                                                                                     ` Jerome Glisse
2019-01-16  2:23                                                                                       ` Jerome Glisse
2019-01-16  4:34                                                                                       ` Dave Chinner
2019-01-16  4:34                                                                                         ` Dave Chinner
2019-01-16 14:50                                                                                         ` Jerome Glisse
2019-01-16 14:50                                                                                           ` Jerome Glisse
2019-01-16 22:51                                                                                           ` Dave Chinner
2019-01-16 22:51                                                                                             ` Dave Chinner
2019-01-16 11:38                                                                         ` Jan Kara
2019-01-16 11:38                                                                           ` Jan Kara
2019-01-16 13:08                                                                           ` Jerome Glisse
2019-01-16 13:08                                                                             ` Jerome Glisse
2019-01-17  5:42                                                                             ` John Hubbard
2019-01-17  5:42                                                                               ` John Hubbard
2019-01-17 15:21                                                                               ` Jerome Glisse
2019-01-17 15:21                                                                                 ` Jerome Glisse
2019-01-18  0:16                                                                                 ` Dave Chinner
2019-01-18  1:59                                                                                   ` Jerome Glisse
2019-01-17  9:30                                                                             ` Jan Kara
2019-01-17  9:30                                                                               ` Jan Kara
2019-01-17 15:17                                                                               ` Jerome Glisse
2019-01-17 15:17                                                                                 ` Jerome Glisse
2019-01-22 15:24                                                                                 ` Jan Kara
2019-01-22 16:46                                                                                   ` Jerome Glisse
2019-01-23 18:02                                                                                     ` Jan Kara
2019-01-23 19:04                                                                                       ` Jerome Glisse
2019-01-29  0:22                                                                                         ` John Hubbard
2019-01-29  1:23                                                                                           ` Jerome Glisse
2019-01-29  6:41                                                                                             ` John Hubbard
2019-01-29 10:12                                                                                               ` Jan Kara
2019-01-30  2:21                                                                                                 ` John Hubbard
2019-01-17  5:25                                                                         ` John Hubbard
2019-01-17  5:25                                                                           ` John Hubbard
2019-01-17  9:04                                                                           ` Jan Kara
2019-01-17  9:04                                                                             ` Jan Kara
2019-01-12  3:14                                                               ` Jerome Glisse
2019-01-12  3:14                                                                 ` Jerome Glisse
2018-12-18 10:33                                   ` Jan Kara
2018-12-18 23:42                                     ` Dave Chinner
2018-12-19  3:03                                       ` Jason Gunthorpe
2018-12-19  5:26                                         ` Dan Williams
2018-12-19 11:19                                           ` Jan Kara
2018-12-19 10:28                                         ` Dave Chinner
2018-12-19 11:35                                           ` Jan Kara
2018-12-19 16:56                                             ` Jason Gunthorpe
2018-12-19 22:33                                             ` Dave Chinner
2018-12-20  9:07                                               ` Jan Kara
2018-12-20 16:54                                               ` Jerome Glisse
2018-12-19 13:24                                       ` Jan Kara
2018-12-08  5:18                       ` Matthew Wilcox
2018-12-12 19:13                         ` John Hubbard
2018-12-08  7:16                       ` Dan Williams
2018-12-08 16:33                         ` Jerome Glisse
2018-12-08 16:48                           ` Christoph Hellwig
2018-12-08 17:47                             ` Jerome Glisse
2018-12-08 18:26                               ` Christoph Hellwig
2018-12-08 18:45                                 ` Jerome Glisse
2018-12-08 18:09                             ` Dan Williams
2018-12-08 18:12                               ` Christoph Hellwig
2018-12-11  6:18                               ` Dave Chinner
2018-12-05  5:52             ` Dan Williams
2018-12-05 11:16       ` Jan Kara
2018-12-04  0:17 ` [PATCH 2/2] infiniband/mm: convert put_page() to put_user_page*() john.hubbard
2018-12-04 17:10 ` [PATCH 0/2] put_user_page*(): start converting the call sites David Laight
2018-12-05  1:05   ` John Hubbard
2018-12-05 14:08     ` David Laight
2018-12-28  8:37       ` Pavel Machek
2019-02-08  7:56 [PATCH 0/2] mm: put_user_page() call site conversion first john.hubbard
2019-02-08  7:56 ` [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions john.hubbard
2019-02-08 10:32   ` Mike Rapoport
2019-02-08 20:44     ` John Hubbard

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