The patch titled
Subject: v4l2: disable filesystem-dax mapping support
has been added to the -mm tree. Its filename is
v4l2-disable-filesystem-dax-mapping-support.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/v4l2-disable-filesystem-dax-mapping-support.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/v4l2-disable-filesystem-dax-mapping-support.patch
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------------------------------------------------------
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>
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 <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
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;
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages.patch
mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages-v3.patch
mm-switch-to-define-pmd_write-instead-of-__have_arch_pmd_write.patch
mm-replace-pud_write-with-pud_access_permitted-in-fault-gup-paths.patch
mm-replace-pud_write-with-pud_access_permitted-in-fault-gup-paths-v3.patch
mm-replace-pmd_write-with-pmd_access_permitted-in-fault-gup-paths.patch
mm-replace-pte_write-with-pte_access_permitted-in-fault-gup-paths.patch
mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch
device-dax-implement-split-to-catch-invalid-munmap-attempts.patch
mm-introduce-get_user_pages_longterm.patch
mm-fail-get_vaddr_frames-for-filesystem-dax-mappings.patch
v4l2-disable-filesystem-dax-mapping-support.patch
ib-core-disable-memory-registration-of-fileystem-dax-vmas.patch