When page is pinned it cannot be moved and its physical address stays the same until pages is unpinned. This is useful functionality to allows userland to implementation DMA access. For example, it is used by vfio in vfio_pin_pages(). However, this functionality breaks memory hotplug/hotremove assumptions that pages in ZONE_MOVABLE can always be migrated. This patch series fixes this issue by forcing new allocations during page pinning to omit ZONE_MOVABLE, and also to migrate any existing pages from ZONE_MOVABLE during pinning. It uses the same scheme logic that is currently used by CMA, and extends the functionality for all allocations. For more information read the discussion [1] about this problem. [1] https://lore.kernel.org/lkml/CA+CK2bBffHBxjmb9jmSKacm0fJMinyt3Nhk8Nx6iudcQSj80_w@xxxxxxxxxxxxxx/ Pavel Tatashin (6): mm/gup: perform check_dax_vmas only when FS_DAX is enabled mm/gup: don't pin migrated cma pages in movable zone mm/gup: make __gup_longterm_locked common mm cma: rename PF_MEMALLOC_NOCMA to PF_MEMALLOC_NOMOVABLE mm: honor PF_MEMALLOC_NOMOVABLE for all allocations mm/gup: migrate pinned pages out of movable zone include/linux/migrate.h | 1 + include/linux/sched.h | 2 +- include/linux/sched/mm.h | 21 +++------ include/trace/events/migrate.h | 3 +- mm/gup.c | 82 +++++++++++++--------------------- mm/hugetlb.c | 4 +- mm/page_alloc.c | 26 ++++++----- 7 files changed, 58 insertions(+), 81 deletions(-) -- 2.25.1
