From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: v4l2: disable filesystem-dax mapping support 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@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reported-by: Jan Kara <jack@xxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Doug Ledford <dledford@xxxxxxxxxx> Cc: Hal Rosenstock <hal.rosenstock@xxxxxxxxx> Cc: Inki Dae <inki.dae@xxxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: Joonyoung Shim <jy0922.shim@xxxxxxxxxxx> Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Cc: Sean Hefty <sean.hefty@xxxxxxxxx> Cc: Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff -puN drivers/media/v4l2-core/videobuf-dma-sg.c~v4l2-disable-filesystem-dax-mapping-support drivers/media/v4l2-core/videobuf-dma-sg.c --- a/drivers/media/v4l2-core/videobuf-dma-sg.c~v4l2-disable-filesystem-dax-mapping-support +++ a/drivers/media/v4l2-core/videobuf-dma-sg.c @@ -185,12 +185,13 @@ static int videobuf_dma_init_user_locked dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n", data, size, dma->nr_pages); - err = get_user_pages(data & PAGE_MASK, dma->nr_pages, + err = get_user_pages_longterm(data & PAGE_MASK, dma->nr_pages, flags, dma->pages, NULL); if (err != dma->nr_pages) { dma->nr_pages = (err >= 0) ? err : 0; - dprintk(1, "get_user_pages: err=%d [%d]\n", err, dma->nr_pages); + dprintk(1, "get_user_pages_longterm: err=%d [%d]\n", err, + dma->nr_pages); return err < 0 ? err : -EINVAL; } return 0; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
