// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/ceph/pagelist.h>

struct ceph_pagelist *ceph_pagelist_alloc(gfp_t gfp_flags)
{
        struct ceph_pagelist *pl;

        pl = kmalloc_obj(*pl, gfp_flags);
        if (!pl)
                return NULL;

        INIT_LIST_HEAD(&pl->head);
        pl->mapped_tail = NULL;
        pl->length = 0;
        pl->room = 0;
        INIT_LIST_HEAD(&pl->free_list);
        pl->num_pages_free = 0;
        refcount_set(&pl->refcnt, 1);

        return pl;
}
EXPORT_SYMBOL(ceph_pagelist_alloc);

static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
{
        if (pl->mapped_tail) {
                struct page *page = list_entry(pl->head.prev, struct page, lru);
                kunmap(page);
                pl->mapped_tail = NULL;
        }
}

void ceph_pagelist_release(struct ceph_pagelist *pl)
{
        if (!refcount_dec_and_test(&pl->refcnt))
                return;
        ceph_pagelist_unmap_tail(pl);
        while (!list_empty(&pl->head)) {
                struct page *page = list_first_entry(&pl->head, struct page,
                                                     lru);
                list_del(&page->lru);
                __free_page(page);
        }
        ceph_pagelist_free_reserve(pl);
        kfree(pl);
}
EXPORT_SYMBOL(ceph_pagelist_release);

static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
{
        struct page *page;

        if (!pl->num_pages_free) {
                page = __page_cache_alloc(GFP_NOFS);
        } else {
                page = list_first_entry(&pl->free_list, struct page, lru);
                list_del(&page->lru);
                --pl->num_pages_free;
        }
        if (!page)
                return -ENOMEM;
        pl->room += PAGE_SIZE;
        ceph_pagelist_unmap_tail(pl);
        list_add_tail(&page->lru, &pl->head);
        pl->mapped_tail = kmap(page);
        return 0;
}

int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len)
{
        while (pl->room < len) {
                size_t bit = pl->room;
                int ret;

                memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK),
                       buf, bit);
                pl->length += bit;
                pl->room -= bit;
                buf += bit;
                len -= bit;
                ret = ceph_pagelist_addpage(pl);
                if (ret)
                        return ret;
        }

        memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK), buf, len);
        pl->length += len;
        pl->room -= len;
        return 0;
}
EXPORT_SYMBOL(ceph_pagelist_append);

/* Allocate enough pages for a pagelist to append the given amount
 * of data without allocating.
 * Returns: 0 on success, -ENOMEM on error.
 */
int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
{
        if (space <= pl->room)
                return 0;
        space -= pl->room;
        space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */

        while (space > pl->num_pages_free) {
                struct page *page = __page_cache_alloc(GFP_NOFS);
                if (!page)
                        return -ENOMEM;
                list_add_tail(&page->lru, &pl->free_list);
                ++pl->num_pages_free;
        }
        return 0;
}
EXPORT_SYMBOL(ceph_pagelist_reserve);

/* Free any pages that have been preallocated. */
int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)
{
        while (!list_empty(&pl->free_list)) {
                struct page *page = list_first_entry(&pl->free_list,
                                                     struct page, lru);
                list_del(&page->lru);
                __free_page(page);
                --pl->num_pages_free;
        }
        BUG_ON(pl->num_pages_free);
        return 0;
}
EXPORT_SYMBOL(ceph_pagelist_free_reserve);