• John Hubbard's avatar
    mm/gup: allow FOLL_FORCE for get_user_pages_fast() · f4000fdf
    John Hubbard authored
    Commit 817be129 ("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: 817be129
    
     ("mm: validate get_user_pages_fast flags")
    Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
    Reviewed-by: default avatarLeon Romanovsky <leonro@mellanox.com>
    Reviewed-by: default avatarJan 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: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    f4000fdf
gup.c 66.7 KB