// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2013
 * Phillip Lougher <phillip@squashfs.org.uk>
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/mutex.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
#include "page_actor.h"

/* Read separately compressed datablock directly into page cache */
int squashfs_readpage_block(struct folio *folio, u64 block, int bsize,
                int expected)
{
        struct page *target_page = &folio->page;
        struct inode *inode = folio->mapping->host;
        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
        loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
        int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
        loff_t start_index = folio->index & ~mask;
        loff_t end_index = start_index | mask;
        loff_t index;
        int i, pages, bytes, res = -ENOMEM;
        struct page **page, *last_page;
        struct squashfs_page_actor *actor;
        void *pageaddr;

        if (end_index > file_end)
                end_index = file_end;

        pages = end_index - start_index + 1;

        page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
        if (page == NULL)
                return res;

        /* Try to grab all the pages covered by the Squashfs block */
        for (i = 0, index = start_index; index <= end_index; index++) {
                page[i] = (index == folio->index) ? target_page :
                        grab_cache_page_nowait(folio->mapping, index);

                if (page[i] == NULL)
                        continue;

                if (PageUptodate(page[i])) {
                        unlock_page(page[i]);
                        put_page(page[i]);
                        continue;
                }

                i++;
        }

        pages = i;

        /*
         * Create a "page actor" which will kmap and kunmap the
         * page cache pages appropriately within the decompressor
         */
        actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
                                                start_index << PAGE_SHIFT);
        if (actor == NULL)
                goto out;

        /* Decompress directly into the page cache buffers */
        res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);

        last_page = squashfs_page_actor_free(actor);

        if (res < 0)
                goto mark_errored;

        if (res != expected || IS_ERR(last_page)) {
                res = -EIO;
                goto mark_errored;
        }

        /* Last page (if present) may have trailing bytes not filled */
        bytes = res % PAGE_SIZE;
        if (end_index == file_end && last_page && bytes) {
                pageaddr = kmap_local_page(last_page);
                memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
                kunmap_local(pageaddr);
        }

        /* Mark pages as uptodate, unlock and release */
        for (i = 0; i < pages; i++) {
                flush_dcache_page(page[i]);
                SetPageUptodate(page[i]);
                unlock_page(page[i]);
                if (page[i] != target_page)
                        put_page(page[i]);
        }

        kfree(page);

        return 0;

mark_errored:
        /* Decompression failed.  Target_page is
         * dealt with by the caller
         */
        for (i = 0; i < pages; i++) {
                if (page[i] == NULL || page[i] == target_page)
                        continue;
                flush_dcache_page(page[i]);
                unlock_page(page[i]);
                put_page(page[i]);
        }

out:
        kfree(page);
        return res;
}