Changes since v1 [1]: * Cleanup local 'vmas' argument (Christoph) * Replace inline IS_ENABLED(CONFIG_FS_DAX) in C code with ifdef versions of get_user_pages_longterm() for the FS_DAX on/off cases (Christoph) * Add a new patch for the get_vaddr_frames() case, this impacts users like V4L2, and the Exynos driver. * Collect Christoph's reviewed-by for the rdma change [1]: https://lwn.net/Articles/738323/ --- Andrew, Here is a new get_user_pages api for cases where a driver intends to keep an elevated page count indefinitely. This is distinct from usages like iov_iter_get_pages where the elevated page counts are transient. The iov_iter_get_pages cases immediately turn around and submit the pages to a device driver which will put_page when the i/o operation completes (under kernel control). In the longterm case userspace is responsible for dropping the page reference at some undefined point in the future. This is untenable for filesystem-dax case where the filesystem is in control of the lifetime of the block / page and needs reasonable limits on how long it can wait for pages in a mapping to become idle. Fixing filesystems to actually wait for dax pages to be idle before blocks from a truncate/hole-punch operation are repurposed is saved for a later patch series. Also, allowing longterm registration of dax mappings is a future patch series that introduces a "map with lease" semantic where the kernel can revoke a lease and force userspace to drop its page references. I have also tagged these for -stable to purposely break cases that might assume that longterm memory registrations for filesystem-dax mappings were supported by the kernel. The behavior regression this policy change implies is one of the reasons we maintain the "dax enabled. Warning: EXPERIMENTAL, use at your own risk" notification when mounting a filesystem in dax mode. It is worth noting the device-dax interface does not suffer the same constraints since it does not support file space management operations like hole-punch. --- Dan Williams (4): mm: introduce get_user_pages_longterm mm: fail get_vaddr_frames() for filesystem-dax mappings [media] v4l2: disable filesystem-dax mapping support IB/core: disable memory registration of fileystem-dax vmas drivers/infiniband/core/umem.c | 2 - drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +- include/linux/fs.h | 14 ++++++ include/linux/mm.h | 13 ++++++ mm/frame_vector.c | 4 ++ mm/gup.c | 64 +++++++++++++++++++++++++++++ 6 files changed, 99 insertions(+), 3 deletions(-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
