mirror of
https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
![Kent Overstreet](/assets/img/avatar_default.png)
this code originally used the page allocator directly, but most code shouldn't do that - PAGE_SIZE varies with architecture, and slab is faster. 4k is also on the large side for typical usage, 512 bytes is a better choice for typical usage that might be somewhat sparse. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
297 lines
6.5 KiB
C
297 lines
6.5 KiB
C
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#include <linux/atomic.h>
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#include <linux/export.h>
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#include <linux/generic-radix-tree.h>
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#include <linux/gfp.h>
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#include <linux/kmemleak.h>
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#define GENRADIX_ARY (GENRADIX_NODE_SIZE / sizeof(struct genradix_node *))
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#define GENRADIX_ARY_SHIFT ilog2(GENRADIX_ARY)
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struct genradix_node {
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union {
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/* Interior node: */
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struct genradix_node *children[GENRADIX_ARY];
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/* Leaf: */
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u8 data[GENRADIX_NODE_SIZE];
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};
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};
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static inline int genradix_depth_shift(unsigned depth)
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{
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return GENRADIX_NODE_SHIFT + GENRADIX_ARY_SHIFT * depth;
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}
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/*
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* Returns size (of data, in bytes) that a tree of a given depth holds:
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*/
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static inline size_t genradix_depth_size(unsigned depth)
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{
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return 1UL << genradix_depth_shift(depth);
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}
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/* depth that's needed for a genradix that can address up to ULONG_MAX: */
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#define GENRADIX_MAX_DEPTH \
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DIV_ROUND_UP(BITS_PER_LONG - GENRADIX_NODE_SHIFT, GENRADIX_ARY_SHIFT)
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#define GENRADIX_DEPTH_MASK \
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((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
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static inline unsigned genradix_root_to_depth(struct genradix_root *r)
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{
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return (unsigned long) r & GENRADIX_DEPTH_MASK;
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}
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static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
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{
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return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
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}
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/*
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* Returns pointer to the specified byte @offset within @radix, or NULL if not
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* allocated
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*/
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void *__genradix_ptr(struct __genradix *radix, size_t offset)
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{
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struct genradix_root *r = READ_ONCE(radix->root);
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struct genradix_node *n = genradix_root_to_node(r);
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unsigned level = genradix_root_to_depth(r);
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if (ilog2(offset) >= genradix_depth_shift(level))
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return NULL;
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while (1) {
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if (!n)
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return NULL;
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if (!level)
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break;
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level--;
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n = n->children[offset >> genradix_depth_shift(level)];
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offset &= genradix_depth_size(level) - 1;
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}
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return &n->data[offset];
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}
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EXPORT_SYMBOL(__genradix_ptr);
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static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
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{
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return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
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}
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static inline void genradix_free_node(struct genradix_node *node)
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{
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kfree(node);
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}
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/*
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* Returns pointer to the specified byte @offset within @radix, allocating it if
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* necessary - newly allocated slots are always zeroed out:
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*/
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void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
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gfp_t gfp_mask)
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{
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struct genradix_root *v = READ_ONCE(radix->root);
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struct genradix_node *n, *new_node = NULL;
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unsigned level;
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/* Increase tree depth if necessary: */
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while (1) {
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struct genradix_root *r = v, *new_root;
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n = genradix_root_to_node(r);
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level = genradix_root_to_depth(r);
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if (n && ilog2(offset) < genradix_depth_shift(level))
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break;
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if (!new_node) {
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new_node = genradix_alloc_node(gfp_mask);
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if (!new_node)
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return NULL;
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}
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new_node->children[0] = n;
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new_root = ((struct genradix_root *)
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((unsigned long) new_node | (n ? level + 1 : 0)));
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if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
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v = new_root;
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new_node = NULL;
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}
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}
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while (level--) {
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struct genradix_node **p =
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&n->children[offset >> genradix_depth_shift(level)];
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offset &= genradix_depth_size(level) - 1;
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n = READ_ONCE(*p);
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if (!n) {
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if (!new_node) {
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new_node = genradix_alloc_node(gfp_mask);
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if (!new_node)
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return NULL;
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}
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if (!(n = cmpxchg_release(p, NULL, new_node)))
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swap(n, new_node);
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}
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}
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if (new_node)
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genradix_free_node(new_node);
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return &n->data[offset];
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}
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EXPORT_SYMBOL(__genradix_ptr_alloc);
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void *__genradix_iter_peek(struct genradix_iter *iter,
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struct __genradix *radix,
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size_t objs_per_page)
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{
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struct genradix_root *r;
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struct genradix_node *n;
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unsigned level, i;
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if (iter->offset == SIZE_MAX)
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return NULL;
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restart:
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r = READ_ONCE(radix->root);
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if (!r)
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return NULL;
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n = genradix_root_to_node(r);
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level = genradix_root_to_depth(r);
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if (ilog2(iter->offset) >= genradix_depth_shift(level))
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return NULL;
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while (level) {
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level--;
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i = (iter->offset >> genradix_depth_shift(level)) &
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(GENRADIX_ARY - 1);
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while (!n->children[i]) {
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size_t objs_per_ptr = genradix_depth_size(level);
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if (iter->offset + objs_per_ptr < iter->offset) {
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iter->offset = SIZE_MAX;
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iter->pos = SIZE_MAX;
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return NULL;
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}
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i++;
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iter->offset = round_down(iter->offset + objs_per_ptr,
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objs_per_ptr);
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iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) *
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objs_per_page;
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if (i == GENRADIX_ARY)
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goto restart;
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}
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n = n->children[i];
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}
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return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
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}
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EXPORT_SYMBOL(__genradix_iter_peek);
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void *__genradix_iter_peek_prev(struct genradix_iter *iter,
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struct __genradix *radix,
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size_t objs_per_page,
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size_t obj_size_plus_page_remainder)
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{
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struct genradix_root *r;
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struct genradix_node *n;
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unsigned level, i;
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if (iter->offset == SIZE_MAX)
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return NULL;
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restart:
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r = READ_ONCE(radix->root);
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if (!r)
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return NULL;
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n = genradix_root_to_node(r);
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level = genradix_root_to_depth(r);
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if (ilog2(iter->offset) >= genradix_depth_shift(level)) {
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iter->offset = genradix_depth_size(level);
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iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;
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iter->offset -= obj_size_plus_page_remainder;
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iter->pos--;
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}
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while (level) {
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level--;
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i = (iter->offset >> genradix_depth_shift(level)) &
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(GENRADIX_ARY - 1);
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while (!n->children[i]) {
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size_t objs_per_ptr = genradix_depth_size(level);
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iter->offset = round_down(iter->offset, objs_per_ptr);
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iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;
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if (!iter->offset)
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return NULL;
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iter->offset -= obj_size_plus_page_remainder;
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iter->pos--;
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if (!i)
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goto restart;
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--i;
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}
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n = n->children[i];
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}
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return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
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}
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EXPORT_SYMBOL(__genradix_iter_peek_prev);
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static void genradix_free_recurse(struct genradix_node *n, unsigned level)
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{
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if (level) {
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unsigned i;
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for (i = 0; i < GENRADIX_ARY; i++)
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if (n->children[i])
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genradix_free_recurse(n->children[i], level - 1);
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}
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genradix_free_node(n);
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}
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int __genradix_prealloc(struct __genradix *radix, size_t size,
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gfp_t gfp_mask)
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{
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size_t offset;
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for (offset = 0; offset < size; offset += GENRADIX_NODE_SIZE)
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if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
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return -ENOMEM;
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return 0;
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}
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EXPORT_SYMBOL(__genradix_prealloc);
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void __genradix_free(struct __genradix *radix)
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{
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struct genradix_root *r = xchg(&radix->root, NULL);
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genradix_free_recurse(genradix_root_to_node(r),
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genradix_root_to_depth(r));
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}
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EXPORT_SYMBOL(__genradix_free);
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