linux-kernel - [PATCH 1/2] mm/gup: introduce pin_user_pages

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Date:   Sun, 17 May 2020 18:21:56 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Andy Walls <awalls@...metrocast.net>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-media@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, John Hubbard <jhubbard@...dia.com>
Subject: [PATCH 1/2] mm/gup: introduce pin_user_pages_unlocked

Introduce pin_user_pages_unlocked(), which is nearly identical to the
get_user_pages_unlocked() that it wraps, except that it sets FOLL_PIN
and rejects FOLL_GET.

Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
 include/linux/mm.h |  2 ++
 mm/gup.c           | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5a323422d783..a5594ac9ebe3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1702,6 +1702,8 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
 		    unsigned int gup_flags, struct page **pages, int *locked);
 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
 		    struct page **pages, unsigned int gup_flags);
+long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
+		    struct page **pages, unsigned int gup_flags);
 
 int get_user_pages_fast(unsigned long start, int nr_pages,
 			unsigned int gup_flags, struct page **pages);
diff --git a/mm/gup.c b/mm/gup.c
index 87a6a59fe667..50cd9323efff 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2939,3 +2939,20 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
 				     pages, vmas, gup_flags);
 }
 EXPORT_SYMBOL(pin_user_pages);
+
+/*
+ * pin_user_pages_unlocked() is the FOLL_PIN variant of
+ * get_user_pages_unlocked(). Behavior is the same, except that this one sets
+ * FOLL_PIN and rejects FOLL_GET.
+ */
+long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
+			     struct page **pages, unsigned int gup_flags)
+{
+	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
+	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
+		return -EINVAL;
+
+	gup_flags |= FOLL_PIN;
+	return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
+}
+EXPORT_SYMBOL(pin_user_pages_unlocked);

base-commit: b9bbe6ed63b2b9f2c9ee5cbd0f2c946a2723f4ce
prerequisite-patch-id: 0496235d2f0b29f75b9835e63a6923ddad6d0260
prerequisite-patch-id: 2711b9393a74cd0e1fcf48befea3618f7bb1ca9e
prerequisite-patch-id: 95e2521748b3058710fb2a161b2c76389644665b
prerequisite-patch-id: eeae300399f69db2cd61535b40c1f1ee1929195a
prerequisite-patch-id: 9ed26cdb071ab084a204c85a08986806d6bae877
-- 
2.26.2