To simplify the initial implementation device private pages were restricted to only being used for private anonymous. This avoided having to deal with issues related to shared and/or file-backed pagesi early on. This series lifts that restriction by allowing ZONE_DEVICE private pages to exist in the pagecache. As the CPU cannot directly access these pages special care needs to be taken when looking them up in the page-cache. This series solves the problem by always migrating such pages back from device memory when looking them up in the pagecache. This is similar to how device private pages work for anonymous memory, where a CPU fault on the device memory will always trigger a migration back to CPU system memory. Initially this series only allows for read-only migration - this is because the call to migrate pages back will always reload the data from backing storage. It then introduces a callback that drivers may implement to actually copy any modified data back as required. Drivers are expected to call set_page_dirty() when copying data back to ensure it hits the backing store. This series is an early draft implementation - in particular error handling is not dealt with and I'm not sure that the management of PTE write bits is entirely correct. Much more testing of all the various filesystem corner cases is also required. The aim of this series is to get early feedback on the overall concept of putting device private pages in the pagecache before fleshing out the implementation further. Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> Alistair Popple (6): mm/migrate_device.c: Don't read dirty bit of non-present PTEs mm/migrate: Support file-backed pages with migrate_vma mm: Allow device private pages to exist in page cache mm: Implement writeback for share device private pages selftests/hmm: Add file-backed migration tests nouveau: Add SVM support for migrating file-backed pages to the GPU drivers/gpu/drm/nouveau/nouveau_dmem.c | 24 ++- include/linux/memremap.h | 2 +- include/linux/migrate.h | 6 +- lib/test_hmm.c | 27 ++- mm/filemap.c | 41 ++++- mm/memory.c | 9 +- mm/memremap.c | 1 +- mm/migrate.c | 42 ++-- mm/migrate_device.c | 114 +++++++++++- mm/rmap.c | 2 +- tools/testing/selftests/mm/hmm-tests.c | 252 +++++++++++++++++++++++++- 11 files changed, 489 insertions(+), 31 deletions(-) base-commit: 0ad2507d5d93f39619fc42372c347d6006b64319 -- git-series 0.9.1
