From e7638488434415aa478e78435cac8f0365737638 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 16 May 2018 11:46:08 -0700 Subject: mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS In preparation for fixing dax-dma-vs-unmap issues, filesystems need to be able to rely on the fact that they will get wakeups on dev_pagemap page-idle events. Introduce MEMORY_DEVICE_FS_DAX and generic_dax_page_free() as common indicator / infrastructure for dax filesytems to require. With this change there are no users of the MEMORY_DEVICE_HOST designation, so remove it. The HMM sub-system extended dev_pagemap to arrange a callback when a dev_pagemap managed page is freed. Since a dev_pagemap page is free / idle when its reference count is 1 it requires an additional branch to check the page-type at put_page() time. Given put_page() is a hot-path we do not want to incur that check if HMM is not in use, so a static branch is used to avoid that overhead when not necessary. Now, the FS_DAX implementation wants to reuse this mechanism for receiving dev_pagemap ->page_free() callbacks. Rework the HMM-specific static-key into a generic mechanism that either HMM or FS_DAX code paths can enable. For ARCH=um builds, and any other arch that lacks ZONE_DEVICE support, care must be taken to compile out the DEV_PAGEMAP_OPS infrastructure. However, we still need to support FS_DAX in the FS_DAX_LIMITED case implemented by the s390/dcssblk driver. Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: Michal Hocko Reported-by: kbuild test robot Reported-by: Thomas Meyer Reported-by: Dave Jiang Cc: "Jérôme Glisse" Reviewed-by: Jan Kara Reviewed-by: Christoph Hellwig Signed-off-by: Dan Williams --- mm/Kconfig | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index d5004d82a1d6..bf9d6366bced 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -692,6 +692,9 @@ config ARCH_HAS_HMM config MIGRATE_VMA_HELPER bool +config DEV_PAGEMAP_OPS + bool + config HMM bool select MIGRATE_VMA_HELPER @@ -712,6 +715,7 @@ config DEVICE_PRIVATE bool "Unaddressable device memory (GPU memory, ...)" depends on ARCH_HAS_HMM select HMM + select DEV_PAGEMAP_OPS help Allows creation of struct pages to represent unaddressable device @@ -722,6 +726,7 @@ config DEVICE_PUBLIC bool "Addressable device memory (like GPU memory)" depends on ARCH_HAS_HMM select HMM + select DEV_PAGEMAP_OPS help Allows creation of struct pages to represent addressable device -- cgit v1.2.3-55-g7522