From: Dan Williams <dan.j.williams@intel.com>
To: akpm@linux-foundation.org
Cc: Jan Kara <jack@suse.cz>,
linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, linux-mm@kvack.org,
Mauro Carvalho Chehab <mchehab@kernel.org>,
hch@lst.de, linux-media@vger.kernel.org
Subject: [PATCH v3 3/4] [media] v4l2: disable filesystem-dax mapping support
Date: Wed, 29 Nov 2017 10:05:46 -0800 [thread overview]
Message-ID: <151197874598.26211.6120423884702550000.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
In-Reply-To: <151197872943.26211.6551382719053304996.stgit@dwillia2-desk3.amr.corp.intel.com>
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.
Reported-by: Jan Kara <jack@suse.cz>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Cc: <stable@vger.kernel.org>
Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
index 0b5c43f7e020..f412429cf5ba 100644
--- a/drivers/media/v4l2-core/videobuf-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
@@ -185,12 +185,13 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma,
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;
--
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next prev parent reply other threads:[~2017-11-29 18:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 18:05 [PATCH v3 0/4] introduce get_user_pages_longterm() Dan Williams
2017-11-29 18:05 ` [PATCH v3 1/4] mm: introduce get_user_pages_longterm Dan Williams
2017-11-30 9:53 ` Michal Hocko
2017-11-30 16:39 ` Dan Williams
2017-11-30 17:42 ` Michal Hocko
2017-11-30 18:03 ` Dan Williams
2017-11-30 18:17 ` Michal Hocko
2017-11-30 18:32 ` Dan Williams
2017-11-30 19:01 ` Jason Gunthorpe
2017-12-01 10:12 ` Michal Hocko
2017-12-01 16:02 ` Jason Gunthorpe
2017-12-01 16:29 ` Dan Williams
2017-12-01 16:31 ` Jason Gunthorpe
2017-12-04 9:31 ` Michal Hocko
2017-12-04 17:01 ` Dan Williams
2017-11-29 18:05 ` [PATCH v3 2/4] mm: fail get_vaddr_frames() for filesystem-dax mappings Dan Williams
2017-11-29 18:05 ` Dan Williams [this message]
2017-11-29 18:05 ` [PATCH v3 4/4] IB/core: disable memory registration of fileystem-dax vmas Dan Williams
2017-11-29 18:36 ` Jason Gunthorpe
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