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Reimplement IDR and IDA using the radix tree

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The IDR is very similar to the radix tree.  It has some functionality that
the radix tree did not have (alloc next free, cyclic allocation, a
callback-based for_each, destroy tree), which is readily implementable on
top of the radix tree.  A few small changes were needed in order to use a
tag to represent nodes with free space below them.  More extensive
changes were needed to support storing NULL as a valid entry in an IDR.
Plain radix trees still interpret NULL as a not-present entry.

The IDA is reimplemented as a client of the newly enhanced radix tree.  As
in the current implementation, it uses a bitmap at the last level of the
tree.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2016-12-20 10:27:56 -05:00
parent 0ac398ef39
commit 0a835c4f09
13 changed files with 993 additions and 1124 deletions
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49
include/linux/radix-tree.h
View file

@ -105,7 +105,10 @@ struct radix_tree_node {
unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};
/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
/* The top bits of gfp_mask are used to store the root tags and the IDR flag */
#define ROOT_IS_IDR ((__force gfp_t)(1 << __GFP_BITS_SHIFT))
#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT + 1)
struct radix_tree_root {
gfp_t gfp_mask;
struct radix_tree_node __rcu *rnode;
@ -358,10 +361,14 @@ int radix_tree_split(struct radix_tree_root *, unsigned long index,
unsigned new_order);
int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);
void **idr_get_free(struct radix_tree_root *, struct radix_tree_iter *,
gfp_t, int end);
#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */
#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */
#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */
enum {
RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */
RADIX_TREE_ITER_CONTIG = 0x20, /* stop at first hole */
};
/**
* radix_tree_iter_init - initialize radix tree iterator
@ -402,6 +409,40 @@ radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
void **radix_tree_next_chunk(const struct radix_tree_root *,
struct radix_tree_iter *iter, unsigned flags);
/**
* radix_tree_iter_lookup - look up an index in the radix tree
* @root: radix tree root
* @iter: iterator state
* @index: key to look up
*
* If @index is present in the radix tree, this function returns the slot
* containing it and updates @iter to describe the entry. If @index is not
* present, it returns NULL.
*/
static inline void **radix_tree_iter_lookup(const struct radix_tree_root *root,
struct radix_tree_iter *iter, unsigned long index)
{
radix_tree_iter_init(iter, index);
return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
}
/**
* radix_tree_iter_find - find a present entry
* @root: radix tree root
* @iter: iterator state
* @index: start location
*
* This function returns the slot containing the entry with the lowest index
* which is at least @index. If @index is larger than any present entry, this
* function returns NULL. The @iter is updated to describe the entry found.
*/
static inline void **radix_tree_iter_find(const struct radix_tree_root *root,
struct radix_tree_iter *iter, unsigned long index)
{
radix_tree_iter_init(iter, index);
return radix_tree_next_chunk(root, iter, 0);
}
/**
* radix_tree_iter_retry - retry this chunk of the iteration
* @iter: iterator state