• Dan Williams's avatar
    v4l2: disable filesystem-dax mapping support · b70131de
    Dan Williams authored
    V4L2 memory registrations are incompatible with filesystem-dax that
    needs the ability to revoke dma access to a mapping at will, or
    otherwise allow the kernel to wait for completion of DMA.  The
    filesystem-dax implementation breaks the traditional solution of
    truncate of active file backed mappings since there is no page-cache
    page we can orphan to sustain ongoing DMA.
    
    If v4l2 wants to support long lived DMA mappings it needs to arrange to
    hold a file lease or use some other mechanism so that the kernel can
    coordinate revoking DMA access when the filesystem needs to truncate
    mappings.
    
    Link: http://lkml.kernel.org/r/151068940499.7446.12846708245365671207.stgit@dwillia2-desk3.amr.corp.intel.com
    Fixes: 3565fce3 ("mm, x86: get_user_pages() for dax mappings")
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Reported-by: default avatarJan Kara <jack@suse.cz>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Doug Ledford <dledford@redhat.com>
    Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
    Cc: Inki Dae <inki.dae@samsung.com>
    Cc: Jason Gunthorpe <jgg@mellanox.com>
    Cc: Jeff Moyer <jmoyer@redhat.com>
    Cc: Joonyoung Shim <jy0922.shim@samsung.com>
    Cc: Kyungmin Park <kyungmin.park@samsung.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
    Cc: Sean Hefty <sean.hefty@intel.com>
    Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    b70131de
videobuf-dma-sg.c 16.4 KB