Linux-kselftest Archive on lore.kernel.org
 help / color / Atom feed
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: John Hubbard <jhubbard@nvidia.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Chinner" <david@fromorbit.com>,
	"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Michal Hocko" <mhocko@suse.com>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Matthew Wilcox" <willy@infradead.org>,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 04/12] mm: introduce page_ref_sub_return()
Date: Wed, 5 Feb 2020 14:23:43 +0300
Message-ID: <20200205112343.e2vpcylgrobfcxlo@box> (raw)
In-Reply-To: <20200204234117.2974687-5-jhubbard@nvidia.com>

On Tue, Feb 04, 2020 at 03:41:09PM -0800, John Hubbard wrote:
> An upcoming patch requires subtracting a large chunk of refcounts from
> a page, and checking what the resulting refcount is. This is a little
> different than the usual "check for zero refcount" that many of the
> page ref functions already do. However, it is similar to a few other
> routines that (like this one) are generally useful for things such as
> 1-based refcounting.
> 
> Add page_ref_sub_return(), that subtracts a chunk of refcounts
> atomically, and returns an atomic snapshot of the result.
> 
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  include/linux/page_ref.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
> index 14d14beb1f7f..a0e171265b79 100644
> --- a/include/linux/page_ref.h
> +++ b/include/linux/page_ref.h
> @@ -102,6 +102,15 @@ static inline void page_ref_sub(struct page *page, int nr)
>  		__page_ref_mod(page, -nr);
>  }
>  
> +static inline int page_ref_sub_return(struct page *page, int nr)
> +{
> +	int ret = atomic_sub_return(nr, &page->_refcount);
> +
> +	if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))

s/__tracepoint_page_ref_mod/__tracepoint_page_ref_mod_and_return/

> +		__page_ref_mod_and_return(page, -nr, ret);
> +	return ret;
> +}
> +
>  static inline void page_ref_inc(struct page *page)
>  {
>  	atomic_inc(&page->_refcount);
> -- 
> 2.25.0
> 

-- 
 Kirill A. Shutemov

  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04 23:41 [PATCH v4 00/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 01/12] mm: dump_page(): better diagnostics for compound pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 02/12] mm/gup: split get_user_pages_remote() into two routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 03/12] mm/gup: pass a flags arg to __gup_device_* functions John Hubbard
2020-02-04 23:41 ` [PATCH v4 04/12] mm: introduce page_ref_sub_return() John Hubbard
2020-02-05  9:23   ` Jan Kara
2020-02-05 11:23   ` Kirill A. Shutemov [this message]
2020-02-04 23:41 ` [PATCH v4 05/12] mm/gup: pass gup flags to two more routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 06/12] mm/gup: require FOLL_GET for get_user_pages_fast() John Hubbard
2020-02-04 23:41 ` [PATCH v4 07/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-05 11:35   ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 08/12] mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 09/12] mm: dump_page(): better diagnostics for huge pinned pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting John Hubbard
2020-02-05  9:37   ` Jan Kara
2020-02-05 23:13     ` John Hubbard
2020-02-05 11:43   ` Kirill A. Shutemov
2020-02-05 23:58     ` John Hubbard
2020-02-04 23:41 ` [PATCH v4 11/12] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2020-02-05 11:46   ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 12/12] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200205112343.e2vpcylgrobfcxlo@box \
    --to=kirill@shutemov.name \
    --cc=akpm@linux-foundation.org \
    --cc=corbet@lwn.net \
    --cc=dan.j.williams@intel.com \
    --cc=david@fromorbit.com \
    --cc=hch@infradead.org \
    --cc=ira.weiny@intel.com \
    --cc=jack@suse.cz \
    --cc=jgg@ziepe.ca \
    --cc=jglisse@redhat.com \
    --cc=jhubbard@nvidia.com \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=mhocko@suse.com \
    --cc=mike.kravetz@oracle.com \
    --cc=shuah@kernel.org \
    --cc=vbabka@suse.cz \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-kselftest Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-kselftest/0 linux-kselftest/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-kselftest linux-kselftest/ https://lore.kernel.org/linux-kselftest \
		linux-kselftest@vger.kernel.org
	public-inbox-index linux-kselftest

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kselftest


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git