#include <linux/atomic.h>
#include <linux/export.h>
#include <linux/generic-radix-tree.h>
#include <linux/gfp.h>
#include <linux/kmemleak.h>

/*
 * Returns pointer to the specified byte @offset within @radix, or NULL if not
 * allocated
 */
void *__genradix_ptr(struct __genradix *radix, size_t offset)
{
        return __genradix_ptr_inlined(radix, offset);
}
EXPORT_SYMBOL(__genradix_ptr);

/*
 * Returns pointer to the specified byte @offset within @radix, allocating it if
 * necessary - newly allocated slots are always zeroed out:
 */
void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
                           struct genradix_node **preallocated,
                           gfp_t gfp_mask)
{
        struct genradix_root *v = READ_ONCE(radix->root);
        struct genradix_node *n, *new_node = NULL;
        unsigned level;

        if (preallocated)
                swap(new_node, *preallocated);

        /* Increase tree depth if necessary: */
        while (1) {
                struct genradix_root *r = v, *new_root;

                n       = genradix_root_to_node(r);
                level   = genradix_root_to_depth(r);

                if (n && ilog2(offset) < genradix_depth_shift(level))
                        break;

                if (!new_node) {
                        new_node = genradix_alloc_node(gfp_mask);
                        if (!new_node)
                                return NULL;
                }

                new_node->children[0] = n;
                new_root = ((struct genradix_root *)
                            ((unsigned long) new_node | (n ? level + 1 : 0)));

                if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
                        v = new_root;
                        new_node = NULL;
                } else {
                        new_node->children[0] = NULL;
                }
        }

        while (level--) {
                struct genradix_node **p =
                        &n->children[offset >> genradix_depth_shift(level)];
                offset &= genradix_depth_size(level) - 1;

                n = READ_ONCE(*p);
                if (!n) {
                        if (!new_node) {
                                new_node = genradix_alloc_node(gfp_mask);
                                if (!new_node)
                                        return NULL;
                        }

                        if (!(n = cmpxchg_release(p, NULL, new_node)))
                                swap(n, new_node);
                }
        }

        if (new_node)
                genradix_free_node(new_node);

        return &n->data[offset];
}
EXPORT_SYMBOL(__genradix_ptr_alloc);

void *__genradix_iter_peek(struct genradix_iter *iter,
                           struct __genradix *radix,
                           size_t objs_per_page)
{
        struct genradix_root *r;
        struct genradix_node *n;
        unsigned level, i;

        if (iter->offset == SIZE_MAX)
                return NULL;

restart:
        r = READ_ONCE(radix->root);
        if (!r)
                return NULL;

        n       = genradix_root_to_node(r);
        level   = genradix_root_to_depth(r);

        if (ilog2(iter->offset) >= genradix_depth_shift(level))
                return NULL;

        while (level) {
                level--;

                i = (iter->offset >> genradix_depth_shift(level)) &
                        (GENRADIX_ARY - 1);

                while (!n->children[i]) {
                        size_t objs_per_ptr = genradix_depth_size(level);

                        if (iter->offset + objs_per_ptr < iter->offset) {
                                iter->offset    = SIZE_MAX;
                                iter->pos       = SIZE_MAX;
                                return NULL;
                        }

                        i++;
                        iter->offset = round_down(iter->offset + objs_per_ptr,
                                                  objs_per_ptr);
                        iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) *
                                objs_per_page;
                        if (i == GENRADIX_ARY)
                                goto restart;
                }

                n = n->children[i];
        }

        return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
}
EXPORT_SYMBOL(__genradix_iter_peek);

void *__genradix_iter_peek_prev(struct genradix_iter *iter,
                                struct __genradix *radix,
                                size_t objs_per_page,
                                size_t obj_size_plus_page_remainder)
{
        struct genradix_root *r;
        struct genradix_node *n;
        unsigned level, i;

        if (iter->offset == SIZE_MAX)
                return NULL;

restart:
        r = READ_ONCE(radix->root);
        if (!r)
                return NULL;

        n       = genradix_root_to_node(r);
        level   = genradix_root_to_depth(r);

        if (ilog2(iter->offset) >= genradix_depth_shift(level)) {
                iter->offset = genradix_depth_size(level);
                iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;

                iter->offset -= obj_size_plus_page_remainder;
                iter->pos--;
        }

        while (level) {
                level--;

                i = (iter->offset >> genradix_depth_shift(level)) &
                        (GENRADIX_ARY - 1);

                while (!n->children[i]) {
                        size_t objs_per_ptr = genradix_depth_size(level);

                        iter->offset = round_down(iter->offset, objs_per_ptr);
                        iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;

                        if (!iter->offset)
                                return NULL;

                        iter->offset -= obj_size_plus_page_remainder;
                        iter->pos--;

                        if (!i)
                                goto restart;
                        --i;
                }

                n = n->children[i];
        }

        return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
}
EXPORT_SYMBOL(__genradix_iter_peek_prev);

static void genradix_free_recurse(struct genradix_node *n, unsigned level)
{
        if (level) {
                unsigned i;

                for (i = 0; i < GENRADIX_ARY; i++)
                        if (n->children[i])
                                genradix_free_recurse(n->children[i], level - 1);
        }

        genradix_free_node(n);
}

int __genradix_prealloc(struct __genradix *radix, size_t size,
                        gfp_t gfp_mask)
{
        size_t offset;

        for (offset = 0; offset < size; offset += GENRADIX_NODE_SIZE)
                if (!__genradix_ptr_alloc(radix, offset, NULL, gfp_mask))
                        return -ENOMEM;

        return 0;
}
EXPORT_SYMBOL(__genradix_prealloc);

void __genradix_free(struct __genradix *radix)
{
        struct genradix_root *r = xchg(&radix->root, NULL);

        genradix_free_recurse(genradix_root_to_node(r),
                              genradix_root_to_depth(r));
}
EXPORT_SYMBOL(__genradix_free);