From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "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>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
"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>,
"John Hubbard" <jhubbard@nvidia.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCH v6 03/12] mm: introduce page_ref_sub_return()
Date: Mon, 10 Feb 2020 16:15:27 -0800 [thread overview]
Message-ID: <20200211001536.1027652-4-jhubbard@nvidia.com> (raw)
In-Reply-To: <20200211001536.1027652-1-jhubbard@nvidia.com>
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.
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
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..d27701199a4d 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_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
next prev parent reply other threads:[~2020-02-11 0:15 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 0:15 [PATCH v6 00/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-11 0:15 ` [PATCH v6 01/12] mm/gup: split get_user_pages_remote() into two routines John Hubbard
2020-02-11 0:15 ` [PATCH v6 02/12] mm/gup: pass a flags arg to __gup_device_* functions John Hubbard
2020-02-11 0:15 ` John Hubbard [this message]
2020-02-11 0:15 ` [PATCH v6 04/12] mm/gup: pass gup flags to two more routines John Hubbard
2020-02-11 0:15 ` [PATCH v6 05/12] mm/gup: require FOLL_GET for get_user_pages_fast() John Hubbard
2020-02-11 0:15 ` [PATCH v6 06/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-04-24 18:18 ` [regression] " Alex Williamson
2020-04-24 19:20 ` John Hubbard
2020-04-24 20:15 ` Alex Williamson
2020-04-24 22:58 ` John Hubbard
2020-04-28 16:54 ` [regression?] " Alex Williamson
2020-04-28 17:49 ` Jason Gunthorpe
2020-04-28 19:07 ` Alex Williamson
2020-04-28 19:22 ` Jason Gunthorpe
2020-04-28 20:12 ` Alex Williamson
2020-04-29 0:29 ` Jason Gunthorpe
2020-04-29 19:56 ` Alex Williamson
2020-04-29 23:03 ` Jason Gunthorpe
2020-02-11 0:15 ` [PATCH v6 07/12] mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages John Hubbard
2020-02-11 0:15 ` [PATCH v6 08/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting John Hubbard
2020-02-12 9:17 ` Jan Kara
2020-02-11 0:15 ` [PATCH v6 09/12] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2020-02-11 0:15 ` [PATCH v6 10/12] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2020-02-11 0:15 ` [PATCH v6 11/12] mm: Improve dump_page() for compound pages John Hubbard
2020-02-11 0:15 ` [PATCH v6 12/12] mm: dump_page(): additional diagnostics for huge pinned pages John Hubbard
2020-02-11 13:21 ` Kirill A. Shutemov
2020-02-12 2:10 ` John Hubbard
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