[18/54] mm/gup: introduce pin_user_pages_locked()

Commit Message

Andrew Morton June 8, 2020, 4:41 a.m. UTC

From: John Hubbard <[e-mail]>
Subject: mm/gup: introduce pin_user_pages_locked()

Patch series "mm/gup: introduce pin_user_pages_locked(), use it in frame_vector.c", v2.

This adds yet one more pin_user_pages*() variant, and uses that to convert
mm/frame_vector.c.

With this, along with maybe 20 or 30 other recent patches in various
trees, we are close to having the relevant gup call sites converted--with
the notable exception of the bio/block layer.


This patch (of 2):

Introduce pin_user_pages_locked(), which is nearly identical to
get_user_pages_locked() except that it sets FOLL_PIN and rejects FOLL_GET.

As with other pairs of get_user_pages*() and pin_user_pages() API calls,
it's prudent to assert that FOLL_PIN is *not* set in the get_user_pages*()
call, so add that as part of this.

[[e-mail]: v2]
  Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: John Hubbard <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Acked-by: Pankaj Gupta <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Jérôme Glisse <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Cc: Souptick Joarder <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/mm.h |    2 ++
 mm/gup.c           |   36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

Patch

--- a/include/linux/mm.h~mm-gup-introduce-pin_user_pages_locked
+++ a/include/linux/mm.h
@@ -1706,6 +1706,8 @@  long pin_user_pages(unsigned long start,
 		    struct vm_area_struct **vmas);
 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
 		    unsigned int gup_flags, struct page **pages, int *locked);
+long pin_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,
--- a/mm/gup.c~mm-gup-introduce-pin_user_pages_locked
+++ a/mm/gup.c
@@ -2035,6 +2035,12 @@  long get_user_pages_locked(unsigned long
 	 */
 	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
 		return -EINVAL;
+	/*
+	 * FOLL_PIN must only be set internally by the pin_user_pages*() APIs,
+	 * never directly by the caller, so enforce that:
+	 */
+	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
+		return -EINVAL;
 
 	return __get_user_pages_locked(current, current->mm, start, nr_pages,
 				       pages, NULL, locked,
@@ -3058,3 +3064,33 @@  long pin_user_pages_unlocked(unsigned lo
 	return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
 }
 EXPORT_SYMBOL(pin_user_pages_unlocked);
+
+/*
+ * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
+ * Behavior is the same, except that this one sets FOLL_PIN and rejects
+ * FOLL_GET.
+ */
+long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
+			   unsigned int gup_flags, struct page **pages,
+			   int *locked)
+{
+	/*
+	 * FIXME: Current FOLL_LONGTERM behavior is incompatible with
+	 * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
+	 * vmas.  As there are no users of this flag in this call we simply
+	 * disallow this option for now.
+	 */
+	if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
+		return -EINVAL;
+
+	/* 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_locked(current, current->mm, start, nr_pages,
+				       pages, NULL, locked,
+				       gup_flags | FOLL_TOUCH);
+}
+EXPORT_SYMBOL(pin_user_pages_locked);
+