Commit 104acc32 authored by John Hubbard's avatar John Hubbard Committed by Linus Torvalds
Browse files

mm/gup: introduce pin_user_pages_fast_only() 



This is the FOLL_PIN equivalent of __get_user_pages_fast(), except with a
more descriptive name, and gup_flags instead of a boolean "write" in the
argument list.

Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: "Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://lkml.kernel.org/r/20200519002124.2025955-4-jhubbard@nvidia.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 376a34ef

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -1827,6 +1827,8 @@ extern int mprotect_fixup(struct vm_area_struct *vma, 
 */

int __get_user_pages_fast(unsigned long start, int nr_pages, int write,

			  struct page **pages);

int pin_user_pages_fast_only(unsigned long start, int nr_pages,

			     unsigned int gup_flags, struct page **pages);

/*

 * per-process(per-mm_struct) statistics.

 */

mm/gup.c

+36 −0
Original line number Diff line number Diff line
@@ -2917,6 +2917,42 @@ int pin_user_pages_fast(unsigned long start, int nr_pages, 
}

EXPORT_SYMBOL_GPL(pin_user_pages_fast);



/*

 * This is the FOLL_PIN equivalent of __get_user_pages_fast(). Behavior is the

 * same, except that this one sets FOLL_PIN instead of FOLL_GET.

 *

 * The API rules are the same, too: no negative values may be returned.

 */

int pin_user_pages_fast_only(unsigned long start, int nr_pages,

			     unsigned int gup_flags, struct page **pages)

{

	int nr_pinned;



	/*

	 * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API

	 * rules require returning 0, rather than -errno:

	 */

	if (WARN_ON_ONCE(gup_flags & FOLL_GET))

		return 0;

	/*

	 * FOLL_FAST_ONLY is required in order to match the API description of

	 * this routine: no fall back to regular ("slow") GUP.

	 */

	gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY);

	nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,

						 pages);

	/*

	 * This routine is not allowed to return negative values. However,

	 * internal_get_user_pages_fast() *can* return -errno. Therefore,

	 * correct for that here:

	 */

	if (nr_pinned < 0)

		nr_pinned = 0;



	return nr_pinned;

}

EXPORT_SYMBOL_GPL(pin_user_pages_fast_only);



/**

 * pin_user_pages_remote() - pin pages of a remote process (task != current)

 *

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