Changes since v2 [1]:
* Fix yet more compile breakage in the FS_DAX=n and DEV_DAX=y case. (0day robot)
[1]: https://lists.01.org/pipermail/linux-nvdimm/2018-February/014046.html
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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.
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Dan Williams (6): dax: fix vma_is_fsdax() helper dax: fix dax_mapping() definition in the FS_DAX=n + DEV_DAX=y case xfs, dax: introduce IS_FSDAX() 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 +++++++++++++++--- fs/xfs/xfs_file.c | 14 +++++++------- fs/xfs/xfs_ioctl.c | 4 ++-- fs/xfs/xfs_iomap.c | 6 +++--- fs/xfs/xfs_reflink.c | 2 +- include/linux/dax.h | 9 ++++++--- include/linux/fs.h | 8 ++++++-- 7 files changed, 40 insertions(+), 21 deletions(-)