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.

[jhubbard@nvidia.com: v2]
Link: http://lkml.kernel.org/r/20200531234131.770697-2-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Link: http://lkml.kernel.org/r/20200531234131.770697-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20200527223243.884385-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20200527223243.884385-2-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 22010c4..9d60421 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1706,6 +1706,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
                    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,

diff --git a/mm/gup.c b/mm/gup.c
index 9d1bf3e..5ce0a99 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2035,6 +2035,12 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
         */
        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 +3064,32 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
        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);