From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> 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. Since version 10, I've fixed a few bugs. - There were some places in f2fs where the spinlock was being taken in a not-irq-safe manner. I spotted it by review, but lockdep would have noticed if anybody had tested this patchset on f2fs. - Fixed the bug that Mike Kravetz found where we could end up in an infinite loop when doing a tagged iteration. - Added UBSAN to the userspace testing framework and fixed some problems that it caught (shifting a negative number, shifting by BITS_PER_LONG). - Fixed an unlikely bug in shmem_partial_swap_usage() where I'd forgotten to call xas_retry() in an RCU-protected iteration. - Added a patch to fix dax_load_hole; it wasn't returning errors properly. Things that aren't bug fixes: - dax_layout_busy_page() got removed, so I dropped the adaptation of that function. - Made __test_set_page_writeback more efficient by only walking the tree once instead of up to three times (once per tag). - Redid the shmem_wait_for_pins / shmem_tag_pins patches so they share an xa_state between them. Cuts down stack usage a bit. - Removed more radix tree functionality that's not being used - radix_tree_for_each_contig - radix_tree_update_node_t - radix_tree_clear_tags This is against next-20180413. If you're going to review anything, please review anything in patches 16 and higher; they're the ones mostly missing review, and most likely where the bugs are going to be. Matthew Wilcox (63): 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_wait_for_pins to XArray memfd: Convert shmem_tag_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: Fix use of zero page dax: dax_insert_mapping_entry always succeeds dax: Rename some functions dax: Hash on XArray instead of mapping dax: Convert dax_insert_pfn_mkwrite to XArray dax: Convert __dax_invalidate_entry to XArray dax: Convert dax writeback to XArray dax: Convert page fault handlers to XArray dax: Return fault code from dax_load_hole page cache: Finish XArray conversion radix tree: Remove unused functions radix tree: Remove radix_tree_update_node_t radix tree: Remove radix_tree_clear_tags .clang-format | 1 - Documentation/core-api/index.rst | 1 + Documentation/core-api/xarray.rst | 361 ++++ MAINTAINERS | 12 + arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +- arch/powerpc/include/asm/nohash/64/pgtable.h | 4 +- drivers/gpu/drm/i915/i915_gem.c | 17 +- drivers/staging/lustre/lustre/llite/glimpse.c | 12 +- .../staging/lustre/lustre/mdc/mdc_request.c | 16 +- fs/btrfs/compression.c | 6 +- fs/btrfs/extent_io.c | 12 +- fs/buffer.c | 14 +- fs/dax.c | 725 +++---- fs/ext4/inode.c | 2 +- fs/f2fs/data.c | 5 +- fs/f2fs/dir.c | 2 +- fs/f2fs/inline.c | 4 +- fs/f2fs/node.c | 9 +- fs/fs-writeback.c | 25 +- fs/gfs2/aops.c | 2 +- fs/inode.c | 2 +- fs/nfs/blocklayout/blocklayout.c | 2 +- fs/nilfs2/btnode.c | 37 +- fs/nilfs2/page.c | 72 +- fs/proc/task_mmu.c | 2 +- include/linux/fs.h | 63 +- include/linux/pagemap.h | 10 +- include/linux/pagevec.h | 8 +- include/linux/radix-tree.h | 133 +- include/linux/swap.h | 22 +- include/linux/swapops.h | 19 +- include/linux/xarray.h | 1010 ++++++++++ lib/Makefile | 2 +- lib/idr.c | 67 +- lib/radix-tree.c | 571 +----- lib/xarray.c | 1681 +++++++++++++++++ mm/filemap.c | 723 +++---- mm/huge_memory.c | 17 +- mm/khugepaged.c | 177 +- mm/madvise.c | 2 +- mm/memcontrol.c | 2 +- mm/migrate.c | 41 +- mm/mincore.c | 2 +- mm/page-writeback.c | 72 +- mm/readahead.c | 10 +- mm/shmem.c | 301 ++- mm/swap.c | 6 +- mm/swap_state.c | 119 +- mm/truncate.c | 27 +- mm/vmscan.c | 2 +- mm/workingset.c | 71 +- tools/include/linux/spinlock.h | 13 +- tools/testing/radix-tree/.gitignore | 2 + tools/testing/radix-tree/Makefile | 15 +- tools/testing/radix-tree/benchmark.c | 91 - tools/testing/radix-tree/idr-test.c | 6 +- tools/testing/radix-tree/linux/bug.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/main.c | 12 +- tools/testing/radix-tree/multiorder.c | 272 +-- tools/testing/radix-tree/regression1.c | 68 +- tools/testing/radix-tree/regression3.c | 22 - tools/testing/radix-tree/tag_check.c | 32 +- tools/testing/radix-tree/test.c | 53 +- tools/testing/radix-tree/test.h | 6 + tools/testing/radix-tree/xarray-test.c | 594 ++++++ 70 files changed, 5032 insertions(+), 2684 deletions(-) create mode 100644 Documentation/core-api/xarray.rst 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 -- 2.17.0
