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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 v4 06/12] mm/gup: require FOLL_GET for get_user_pages_fast()
Date: Tue, 4 Feb 2020 15:41:11 -0800
Message-ID: <20200204234117.2974687-7-jhubbard@nvidia.com> (raw)
In-Reply-To: <20200204234117.2974687-1-jhubbard@nvidia.com>

Internal to mm/gup.c, require that get_user_pages_fast()
and __get_user_pages_fast() identify themselves, by setting
FOLL_GET. This is required in order to be able to make decisions
based on "FOLL_PIN, or FOLL_GET, or both or neither are set", in
upcoming patches.

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index e5f75e886663..c8affbea2019 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2390,6 +2390,14 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	unsigned long len, end;
 	unsigned long flags;
 	int nr = 0;
+	/*
+	 * Internally (within mm/gup.c), gup fast variants must set FOLL_GET,
+	 * because gup fast is always a "pin with a +1 page refcount" request.
+	 */
+	unsigned int gup_flags = FOLL_GET;
+
+	if (write)
+		gup_flags |= FOLL_WRITE;
 
 	start = untagged_addr(start) & PAGE_MASK;
 	len = (unsigned long) nr_pages << PAGE_SHIFT;
@@ -2415,7 +2423,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) &&
 	    gup_fast_permitted(start, end)) {
 		local_irq_save(flags);
-		gup_pgd_range(start, end, write ? FOLL_WRITE : 0, pages, &nr);
+		gup_pgd_range(start, end, gup_flags, pages, &nr);
 		local_irq_restore(flags);
 	}
 
@@ -2454,7 +2462,7 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
 	int nr = 0, ret = 0;
 
 	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
-				       FOLL_FORCE | FOLL_PIN)))
+				       FOLL_FORCE | FOLL_PIN | FOLL_GET)))
 		return -EINVAL;
 
 	start = untagged_addr(start) & PAGE_MASK;
@@ -2521,6 +2529,13 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
 	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
 		return -EINVAL;
 
+	/*
+	 * The caller may or may not have explicitly set FOLL_GET; either way is
+	 * OK. However, internally (within mm/gup.c), gup fast variants must set
+	 * FOLL_GET, because gup fast is always a "pin with a +1 page refcount"
+	 * request.
+	 */
+	gup_flags |= FOLL_GET;
 	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast);
-- 
2.25.0


  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
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 ` John Hubbard [this message]
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

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