+ mm-gup-allow-foll_force-for-get_user_pages_fast.patch added to -mm tree

+ mm-gup-allow-foll_force-for-get_user_pages_fast.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/gup: allow FOLL_FORCE for get_user_pages_fast()
has been added to the -mm tree.  Its filename is
     mm-gup-allow-foll_force-for-get_user_pages_fast.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-gup-allow-foll_force-for-get_user_pages_fast.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-allow-foll_force-for-get_user_pages_fast.patch

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------------------------------------------------------
From: John Hubbard <jhubbard@nvidia.com>
Subject: mm/gup: allow FOLL_FORCE for get_user_pages_fast()

Commit 817be129e6f2 ("mm: validate get_user_pages_fast flags") allowed
only FOLL_WRITE and FOLL_LONGTERM to be passed to get_user_pages_fast(). 
This, combined with the fact that get_user_pages_fast() falls back to
"slow gup", which *does* accept FOLL_FORCE, leads to an odd situation: if
you need FOLL_FORCE, you cannot call get_user_pages_fast().

There does not appear to be any reason for filtering out FOLL_FORCE. 
There is nothing in the _fast() implementation that requires that we avoid
writing to the pages.  So it appears to have been an oversight.

Fix by allowing FOLL_FORCE to be set for get_user_pages_fast().

Link: http://lkml.kernel.org/r/20200107224558.2362728-9-jhubbard@nvidia.com
Fixes: 817be129e6f2 ("mm: validate get_user_pages_fast flags")
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Björn Töpel <bjorn.topel@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/gup.c~mm-gup-allow-foll_force-for-get_user_pages_fast
+++ a/mm/gup.c
@@ -2411,7 +2411,8 @@ int get_user_pages_fast(unsigned long st
 	unsigned long addr, len, end;
 	int nr = 0, ret = 0;
 
-	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM)))
+	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
+				       FOLL_FORCE)))
 		return -EINVAL;
 
 	start = untagged_addr(start) & PAGE_MASK;
_

Patches currently in -mm which might be from jhubbard@nvidia.com are

mm-gup-factor-out-duplicate-code-from-four-routines.patch
mm-gup-move-try_get_compound_head-to-top-fix-minor-issues.patch
mm-devmap-refactor-1-based-refcounting-for-zone_device-pages.patch
goldish_pipe-rename-local-pin_user_pages-routine.patch
mm-fix-get_user_pages_remotes-handling-of-foll_longterm.patch
vfio-fix-foll_longterm-use-simplify-get_user_pages_remote-call.patch
mm-gup-allow-foll_force-for-get_user_pages_fast.patch
ib-umem-use-get_user_pages_fast-to-pin-dma-pages.patch
media-v4l2-core-set-pages-dirty-upon-releasing-dma-buffers.patch
mm-gup-introduce-pin_user_pages-and-foll_pin.patch
goldish_pipe-convert-to-pin_user_pages-and-put_user_page.patch
ib-corehwumem-set-foll_pin-via-pin_user_pages-fix-up-odp.patch
mm-process_vm_access-set-foll_pin-via-pin_user_pages_remote.patch
drm-via-set-foll_pin-via-pin_user_pages_fast.patch
fs-io_uring-set-foll_pin-via-pin_user_pages.patch
net-xdp-set-foll_pin-via-pin_user_pages.patch
media-v4l2-core-pin_user_pages-foll_pin-and-put_user_page-conversion.patch
vfio-mm-pin_user_pages-foll_pin-and-put_user_page-conversion.patch
powerpc-book3s64-convert-to-pin_user_pages-and-put_user_page.patch
mm-gup_benchmark-use-proper-foll_write-flags-instead-of-hard-coding-1.patch
mm-tree-wide-rename-put_user_page-to-unpin_user_page.patch