Patch "v4l2: disable filesystem-dax mapping support" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    v4l2: disable filesystem-dax mapping support

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     v4l2-disable-filesystem-dax-mapping-support.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Feb 26 20:55:53 CET 2018
From: Dan Williams <dan.j.williams@intel.com>
Date: Fri, 23 Feb 2018 14:05:54 -0800
Subject: v4l2: disable filesystem-dax mapping support
To: gregkh@linuxfoundation.org
Cc: Jan Kara <jack@suse.cz>, Joonyoung Shim <jy0922.shim@samsung.com>, linux-kernel@vger.kernel.org, Seung-Woo Kim <sw0312.kim@samsung.com>, Doug Ledford <dledford@redhat.com>, stable@vger.kernel.org, Christoph Hellwig <hch@lst.de>, Inki Dae <inki.dae@samsung.com>, Jeff Moyer <jmoyer@redhat.com>, Jason Gunthorpe <jgg@mellanox.com>, Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>, Ross Zwisler <ross.zwisler@linux.intel.com>, Kyungmin Park <kyungmin.park@samsung.com>, Sean Hefty <sean.hefty@intel.com>, Mauro Carvalho Chehab <mchehab@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Hal Rosenstock <hal.rosenstock@gmail.com>, Vlastimil Babka <vbabka@suse.cz>
Message-ID: <151942355435.21775.3892492011172127062.stgit@dwillia2-desk3.amr.corp.intel.com>

From: Dan Williams <dan.j.williams@intel.com>

commit b70131de648c2b997d22f4653934438013f407a1 upstream.

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: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/media/v4l2-core/videobuf-dma-sg.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- 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
 	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 stable-queue which might be from dan.j.williams@intel.com are

queue-4.9/mm-fix-devm_memremap_pages-collision-handling.patch
queue-4.9/ib-core-disable-memory-registration-of-filesystem-dax-vmas.patch
queue-4.9/mm-avoid-spurious-bad-pmd-warning-messages.patch
queue-4.9/mm-introduce-get_user_pages_longterm.patch
queue-4.9/mm-fail-get_vaddr_frames-for-filesystem-dax-mappings.patch
queue-4.9/fs-dax.c-fix-inefficiency-in-dax_writeback_mapping_range.patch
queue-4.9/device-dax-implement-split-to-catch-invalid-munmap-attempts.patch
queue-4.9/v4l2-disable-filesystem-dax-mapping-support.patch
queue-4.9/libnvdimm-dax-fix-1gb-aligned-namespaces-vs-physical-misalignment.patch
queue-4.9/x86-entry-64-clear-extra-registers-beyond-syscall-arguments-to-reduce-speculation-attack-surface.patch
queue-4.9/libnvdimm-fix-integer-overflow-static-analysis-warning.patch