From: Matthew Wilcox <mawil...@microsoft.com> This patchset is, I believe, appropriate for merging for 4.17. It contains the XArray implementation, to eventually replace the radix tree, and converts the page cache to use it.
This conversion keeps the radix tree and XArray data structures in sync at all times. That allows us to convert the page cache one function at a time and should allow for easier bisection. Other than renaming some elements of the structures, the data structures are fundamentally unchanged; a radix tree walk and an XArray walk will touch the same number of cachelines. I have changes planned to the XArray data structure, but those will happen in future patches. Improvements the XArray has over the radix tree: - The radix tree provides operations like other trees do; 'insert' and 'delete'. But what most users really want is an automatically resizing array, and so it makes more sense to give users an API that is like an array -- 'load' and 'store'. We still have an 'insert' operation for users that really want that semantic. - The XArray considers locking as part of its API. This simplifies a lot of users who formerly had to manage their own locking just for the radix tree. It also improves code generation as we can now tell RCU that we're holding a lock and it doesn't need to generate as much fencing code. The other advantage is that tree nodes can be moved (not yet implemented). - GFP flags are now parameters to calls which may need to allocate memory. The radix tree forced users to decide what the allocation flags would be at creation time. It's much clearer to specify them at allocation time. - Memory is not preloaded; we don't tie up dozens of pages on the off chance that the slab allocator fails. Instead, we drop the lock, allocate a new node and retry the operation. We have to convert all the radix tree, IDA and IDR preload users before we can realise this benefit, but I have not yet found a user which cannot be converted. - The XArray provides a cmpxchg operation. The radix tree forces users to roll their own (and at least four have). - Iterators take a 'max' parameter. That simplifies many users and will reduce the amount of iteration done. - Iteration can proceed backwards. We only have one user for this, but since it's called as part of the pagefault readahead algorithm, that seemed worth mentioning. - RCU-protected pointers are not exposed as part of the API. There are some fun bugs where the page cache forgets to use rcu_dereference() in the current codebase. - Value entries gain an extra bit compared to radix tree exceptional entries. That gives us the extra bit we need to put huge page swap entries in the page cache. - Some iterators now take a 'filter' argument instead of having separate iterators for tagged/untagged iterations. The page cache is improved by this: - Shorter, easier to read code - More efficient iterations - Reduction in size of struct address_space - Fewer walks from the top of the data structure; the XArray API encourages staying at the leaf node and conducting operations there. Changes since v8: - Rebased on next-20180313 - David Sterba merged the btrfs filemap_range_has_page patch into the btrfs tree (thanks!) - Darrick Wong merged the xfs patch renaming xa_* to ail_* (thanks!) - Textual conflict with Dave Chinner's removal of a call to memset in fs/inode.c - Textual conflict in lib/Makefile with Dave Young making dump_stack.o confitionally compiled. Changes since v7: - Added acks from Jeff Layton (thanks!) - Renamed the address_space ->pages to ->i_pages - Used GFP_ZONEMASK instead of the more obtuse shifting by 4 (Jeff Layton) - Realised that page_cache_range_empty() and filemap_range_has_page() were essentially the same function, so redid that pair of patches - A few checkpatch fixes - Added an SPDX tag to a missed file - Rebased on next-20180306 - memfd moved out of shmem - nds32 needed its flush_dcache_mmap_lock fixed - mac80211_hwsim had added a use of IDA_INIT - Improved some documentation and commit messages - Split the rearrangement of struct address_space into its own patch (Kirill) - address_space documentation improvements had somehow worked their way into an unrelated patch; move them into the rearrangement patch. - Removed chunks of radix tree functionality that are not used any more. Matthew Wilcox (61): mac80211_hwsim: Use DEFINE_IDA radix tree: Use GFP_ZONEMASK bits of gfp_t for flags arm64: Turn flush_dcache_mmap_lock into a no-op unicore32: Turn flush_dcache_mmap_lock into a no-op Export __set_page_dirty fscache: Use appropriate radix tree accessors xarray: Add the xa_lock to the radix_tree_root page cache: Use xa_lock xarray: Replace exceptional entries xarray: Change definition of sibling entries xarray: Add definition of struct xarray xarray: Define struct xa_node xarray: Add documentation xarray: Add xa_load xarray: Add xa_get_tag, xa_set_tag and xa_clear_tag xarray: Add xa_store xarray: Add xa_cmpxchg and xa_insert xarray: Add xa_for_each xarray: Add xa_extract xarray: Add xa_destroy xarray: Add xas_next and xas_prev xarray: Add xas_create_range xarray: Add MAINTAINERS entry page cache: Rearrange address_space page cache: Convert hole search to XArray page cache: Add and replace pages using the XArray page cache: Convert page deletion to XArray page cache: Convert page cache lookups to XArray page cache: Convert delete_batch to XArray page cache: Remove stray radix comment page cache: Convert filemap_range_has_page to XArray mm: Convert page-writeback to XArray mm: Convert workingset to XArray mm: Convert truncate to XArray mm: Convert add_to_swap_cache to XArray mm: Convert delete_from_swap_cache to XArray mm: Convert __do_page_cache_readahead to XArray mm: Convert page migration to XArray mm: Convert huge_memory to XArray mm: Convert collapse_shmem to XArray mm: Convert khugepaged_scan_shmem to XArray pagevec: Use xa_tag_t shmem: Convert replace to XArray shmem: Convert shmem_confirm_swap to XArray shmem: Convert find_swap_entry to XArray shmem: Convert shmem_add_to_page_cache to XArray shmem: Convert shmem_alloc_hugepage to XArray shmem: Convert shmem_free_swap to XArray shmem: Convert shmem_partial_swap_usage to XArray memfd: Convert shmem_tag_pins to XArray memfd: Convert shmem_wait_for_pins to XArray shmem: Comment fixups btrfs: Convert page cache to XArray fs: Convert buffer to XArray fs: Convert writeback to XArray nilfs2: Convert to XArray f2fs: Convert to XArray lustre: Convert to XArray dax: Convert to XArray page cache: Finish XArray conversion radix tree: Remove unused functions Documentation/cgroup-v1/memory.txt | 2 +- Documentation/core-api/index.rst | 1 + Documentation/core-api/xarray.rst | 361 +++++ Documentation/vm/page_migration | 14 +- MAINTAINERS | 12 + arch/arm/include/asm/cacheflush.h | 6 +- arch/arm64/include/asm/cacheflush.h | 6 +- arch/nds32/include/asm/cacheflush.h | 4 +- arch/nios2/include/asm/cacheflush.h | 6 +- arch/parisc/include/asm/cacheflush.h | 6 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +- arch/powerpc/include/asm/nohash/64/pgtable.h | 4 +- arch/unicore32/include/asm/cacheflush.h | 6 +- drivers/gpu/drm/i915/i915_gem.c | 17 +- drivers/net/wireless/mac80211_hwsim.c | 2 +- drivers/staging/lustre/lustre/llite/glimpse.c | 12 +- drivers/staging/lustre/lustre/mdc/mdc_request.c | 16 +- fs/afs/write.c | 9 +- fs/btrfs/compression.c | 6 +- fs/btrfs/extent_io.c | 26 +- fs/buffer.c | 28 +- fs/cifs/file.c | 9 +- fs/dax.c | 460 +++---- fs/ext4/inode.c | 2 +- fs/f2fs/data.c | 9 +- fs/f2fs/dir.c | 5 +- fs/f2fs/gc.c | 2 +- fs/f2fs/inline.c | 6 +- fs/f2fs/node.c | 10 +- fs/fs-writeback.c | 39 +- fs/fscache/cookie.c | 2 +- fs/fscache/object.c | 2 +- fs/gfs2/aops.c | 2 +- fs/inode.c | 11 +- fs/nfs/blocklayout/blocklayout.c | 2 +- fs/nilfs2/btnode.c | 41 +- fs/nilfs2/page.c | 78 +- fs/proc/task_mmu.c | 2 +- fs/xfs/xfs_aops.c | 15 +- include/linux/backing-dev.h | 14 +- include/linux/fs.h | 67 +- include/linux/idr.h | 22 +- include/linux/mm.h | 3 +- include/linux/pagemap.h | 14 +- include/linux/pagevec.h | 8 +- include/linux/radix-tree.h | 112 +- include/linux/swap.h | 22 +- include/linux/swapops.h | 19 +- include/linux/xarray.h | 1015 ++++++++++++++ kernel/pid.c | 2 +- lib/Makefile | 2 +- lib/idr.c | 65 +- lib/radix-tree.c | 524 ++----- lib/xarray.c | 1667 +++++++++++++++++++++++ mm/filemap.c | 757 ++++------ mm/huge_memory.c | 21 +- mm/khugepaged.c | 182 +-- mm/madvise.c | 2 +- mm/memcontrol.c | 6 +- mm/memfd.c | 102 +- mm/migrate.c | 41 +- mm/mincore.c | 2 +- mm/page-writeback.c | 78 +- mm/readahead.c | 10 +- mm/rmap.c | 4 +- mm/shmem.c | 214 ++- mm/swap.c | 6 +- mm/swap_state.c | 124 +- mm/truncate.c | 45 +- mm/vmscan.c | 14 +- mm/workingset.c | 89 +- tools/include/linux/spinlock.h | 14 +- tools/testing/radix-tree/.gitignore | 2 + tools/testing/radix-tree/Makefile | 15 +- tools/testing/radix-tree/idr-test.c | 6 +- tools/testing/radix-tree/linux/bug.h | 1 + tools/testing/radix-tree/linux/gfp.h | 1 + tools/testing/radix-tree/linux/kconfig.h | 1 + tools/testing/radix-tree/linux/kernel.h | 5 + tools/testing/radix-tree/linux/lockdep.h | 11 + tools/testing/radix-tree/linux/rcupdate.h | 2 + tools/testing/radix-tree/linux/xarray.h | 3 + tools/testing/radix-tree/multiorder.c | 83 +- tools/testing/radix-tree/regression1.c | 68 +- tools/testing/radix-tree/test.c | 53 +- tools/testing/radix-tree/test.h | 6 + tools/testing/radix-tree/xarray-test.c | 549 ++++++++ 87 files changed, 5020 insertions(+), 2298 deletions(-) create mode 100644 Documentation/core-api/xarray.rst create mode 100644 include/linux/xarray.h create mode 100644 lib/xarray.c create mode 100644 tools/testing/radix-tree/linux/kconfig.h create mode 100644 tools/testing/radix-tree/linux/lockdep.h create mode 100644 tools/testing/radix-tree/linux/xarray.h create mode 100644 tools/testing/radix-tree/xarray-test.c -- 2.16.1