This function reserves a slot in the XArray for users which need
to acquire multiple locks before storing their entry in the tree and
so cannot use a plain xa_store().
Signed-off-by: Matthew Wilcox <willy@infradead.org>
This hopefully temporary function is useful for users who have not yet
been converted to multi-index entries.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
This iterator iterates over each entry that is stored in the index or
indices specified by the xa_state. This is intended for use for a
conditional store of a multiindex entry, or to allow entries which are
about to be removed from the xarray to be disposed of properly.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
The xas_next and xas_prev functions move the xas index by one position,
and adjust the rest of the iterator state to match it. This is more
efficient than calling xas_set() as it keeps the iterator at the leaves
of the tree instead of walking the iterator from the root each time.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
This function frees all the internal memory allocated to the xarray
and reinitialises it to be empty.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
The xa_extract function combines the functionality of
radix_tree_gang_lookup() and radix_tree_gang_lookup_tagged().
It extracts entries matching the specified filter into a normal array.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
The xa_for_each iterator allows the user to efficiently walk a range
of the array, executing the loop body once for each entry in that
range that matches the filter. This commit also includes xa_find()
and xa_find_after() which are helper functions for xa_for_each() but
may also be useful in their own right.
In the xas family of functions, we have xas_for_each(), xas_find(),
xas_next_entry(), xas_for_each_tagged(), xas_find_tagged(),
xas_next_tagged() and xas_pause().
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Like cmpxchg(), xa_cmpxchg will only store to the index if the current
entry matches the old entry. It returns the current entry, which is
usually more useful than the errno returned by radix_tree_insert().
For the users who really only want the errno, the xa_insert() wrapper
provides a more convenient calling convention.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
xa_store() differs from radix_tree_insert() in that it will overwrite an
existing element in the array rather than returning an error. This is
the behaviour which most users want, and those that want more complex
behaviour generally want to use the xas family of routines anyway.
For memory allocation, xa_store() will first attempt to request memory
from the slab allocator; if memory is not immediately available, it will
drop the xa_lock and allocate memory, keeping a pointer in the xa_state.
It does not use the per-CPU cache, although those will continue to exist
until all radix tree users are converted to the xarray.
This patch also includes xa_erase() and __xa_erase() for a streamlined
way to store NULL. Since there is no need to allocate memory in order
to store a NULL in the XArray, we do not need to trouble the user with
deciding what memory allocation flags to use.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
XArray marks are like the radix tree tags, only slightly more strongly
typed. They are renamed in order to distinguish them from tagged
pointers. This commit adds the basic get/set/clear operations.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
The xa_load function brings with it a lot of infrastructure; xa_empty(),
xa_is_err(), and large chunks of the XArray advanced API that are used
to implement xa_load.
As the test-suite demonstrates, it is possible to use the XArray functions
on a radix tree. The radix tree functions depend on the GFP flags being
stored in the root of the tree, so it's not possible to use the radix
tree functions on an XArray.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
This is a direct replacement for struct radix_tree_node. A couple of
struct members have changed name, so convert those. Use a #define so
that radix tree users continue to work without change.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
This is a direct replacement for struct radix_tree_root. Some of the
struct members have changed name; convert those, and use a #define so
that radix_tree users continue to work without change.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Instead of storing a pointer to the slot containing the canonical entry,
store the offset of the slot. Produces slightly more efficient code
(~300 bytes) and simplifies the implementation.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries. This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry). It is also a change in emphasis; exceptional entries are
intimidating and different. As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
This results in no change in structure size on 64-bit machines as it
fits in the padding between the gfp_t and the void *. 32-bit machines
will grow the structure from 8 to 12 bytes. Almost all radix trees are
protected with (at least) a spinlock, so as they are converted from
radix trees to xarrays, the data structures will shrink again.
Initialising the spinlock requires a name for the benefit of lockdep, so
RADIX_TREE_INIT() now needs to know the name of the radix tree it's
initialising, and so do IDR_INIT() and IDA_INIT().
Also add the xa_lock() and xa_unlock() family of wrappers to make it
easier to use the lock. If we could rely on -fplan9-extensions in the
compiler, we could avoid all of this syntactic sugar, but that wasn't
added until gcc 4.6.
Link: http://lkml.kernel.org/r/20180313132639.17387-8-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
