[PATCH v8 00/63] XArray v8

From: Matthew Wilcox
Date: Tue Mar 06 2018 - 14:48:26 EST

From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>

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 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 (63):
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
btrfs: Use filemap_range_has_page()
xfs: Rename xa_ elements to ail_
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/btrfs_inode.h | 6 +-
fs/btrfs/compression.c | 6 +-
fs/btrfs/extent_io.c | 26 +-
fs/btrfs/inode.c | 70 -
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 +-
fs/xfs/xfs_buf_item.c | 10 +-
fs/xfs/xfs_dquot.c | 4 +-
fs/xfs/xfs_dquot_item.c | 11 +-
fs/xfs/xfs_inode_item.c | 22 +-
fs/xfs/xfs_log.c | 6 +-
fs/xfs/xfs_log_recover.c | 80 +-
fs/xfs/xfs_trans.c | 18 +-
fs/xfs/xfs_trans_ail.c | 152 +--
fs/xfs/xfs_trans_buf.c | 4 +-
fs/xfs/xfs_trans_priv.h | 42 +-
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 ++++++++
99 files changed, 5200 insertions(+), 2543 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