| From f4000fdf435b8301a11cf85237c561047f8c4c72 Mon Sep 17 00:00:00 2001 |
| From: John Hubbard <jhubbard@nvidia.com> |
| Date: Thu, 30 Jan 2020 22:12:43 -0800 |
| Subject: mm/gup: allow FOLL_FORCE for get_user_pages_fast() |
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| |
| From: John Hubbard <jhubbard@nvidia.com> |
| |
| commit f4000fdf435b8301a11cf85237c561047f8c4c72 upstream. |
| |
| 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> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| mm/gup.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/mm/gup.c |
| +++ b/mm/gup.c |
| @@ -2415,7 +2415,8 @@ 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; |