On Fri, Feb 23, 2018 at 12:55 AM, Haozhong Zhang
> On 02/22/18 23:17 -0800, Dan Williams wrote:
>> Changes since v1 :
>> * Fix the detection of device-dax file instances in vma_is_fsdax().
>> (Haozhong, Gerd)
>> * Fix compile breakage in the FS_DAX=n and DEV_DAX=y case. (0day robot)
>> : https://lists.01.org/pipermail/linux-nvdimm/2018-February/014046.html
>> The vfio interface, like RDMA, wants to setup long term (indefinite)
>> pins of the pages backing an address range so that a guest or userspace
>> driver can perform DMA to the with physical address. Given that this
>> pinning may lead to filesystem operations deadlocking in the
>> filesystem-dax case, the pinning request needs to be rejected.
>> The longer term fix for vfio, RDMA, and any other long term pin user, is
>> to provide a 'pin with lease' mechanism. Similar to the leases that are
>> hold for pNFS RDMA layouts, this userspace lease gives the kernel a way
>> to notify userspace that the block layout of the file is changing and
>> the kernel is revoking access to pinned pages.
>> Dan Williams (5):
>> dax: fix vma_is_fsdax() helper
>> dax: fix dax_mapping() definition in the FS_DAX=n + DEV_DAX=y case
>> dax: fix S_DAX definition
>> dax: short circuit vma_is_fsdax() in the CONFIG_FS_DAX=n case
>> vfio: disable filesystem-dax page pinning
>> drivers/vfio/vfio_iommu_type1.c | 18 +++++++++++++++---
>> include/linux/dax.h | 9 ++++++---
>> include/linux/fs.h | 6 ++++--
>> 3 files changed, 25 insertions(+), 8 deletions(-)
> Tested on QEMU with fs-dax and device-dax as vNVDIMM backends
> respectively with vfio passthrough. The fs-dax case fails QEMU as
> expected, and the device-dax case works normally now.
> Tested-by: Haozhong Zhang <haozhong.zh...@intel.com>
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