[patch 055/128] mm/gup: introduce pin_user_pages_unlocked

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From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: 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.

Link: http://lkml.kernel.org/r/20200518012157.1178336-2-jhubbard@xxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Walls <awalls@xxxxxxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 include/linux/mm.h |    2 ++
 mm/gup.c           |   17 +++++++++++++++++
 2 files changed, 19 insertions(+)

--- a/include/linux/mm.h~mm-gup-introduce-pin_user_pages_unlocked
+++ a/include/linux/mm.h
@@ -1713,6 +1713,8 @@ long get_user_pages_locked(unsigned long
 		    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);
--- a/mm/gup.c~mm-gup-introduce-pin_user_pages_unlocked
+++ a/mm/gup.c
@@ -2960,3 +2960,20 @@ long pin_user_pages(unsigned long start,
 				     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);
_



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