1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (c) 2013
  4 * Phillip Lougher <phillip@squashfs.org.uk>
  5 */
  6
  7#include <linux/fs.h>
  8#include <linux/vfs.h>
  9#include <linux/kernel.h>
 10#include <linux/slab.h>
 11#include <linux/string.h>
 12#include <linux/pagemap.h>
 13#include <linux/mutex.h>
 14
 15#include "squashfs_fs.h"
 16#include "squashfs_fs_sb.h"
 17#include "squashfs_fs_i.h"
 18#include "squashfs.h"
 19#include "page_actor.h"
 20
 21/* Read separately compressed datablock directly into page cache */
 22int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
 23	int expected)
 24
 25{
 26	struct folio *folio = page_folio(target_page);
 27	struct inode *inode = target_page->mapping->host;
 28	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
 29	loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
 30	int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
 31	loff_t start_index = folio->index & ~mask;
 32	loff_t end_index = start_index | mask;
 33	loff_t index;
 34	int i, pages, bytes, res = -ENOMEM;
 35	struct page **page, *last_page;
 36	struct squashfs_page_actor *actor;
 37	void *pageaddr;
 38
 39	if (end_index > file_end)
 40		end_index = file_end;
 41
 42	pages = end_index - start_index + 1;
 43
 44	page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
 45	if (page == NULL)
 46		return res;
 47
 48	/* Try to grab all the pages covered by the Squashfs block */
 49	for (i = 0, index = start_index; index <= end_index; index++) {
 50		page[i] = (index == folio->index) ? target_page :
 51			grab_cache_page_nowait(target_page->mapping, index);
 52
 53		if (page[i] == NULL)
 54			continue;
 55
 56		if (PageUptodate(page[i])) {
 57			unlock_page(page[i]);
 58			put_page(page[i]);
 59			continue;
 60		}
 61
 62		i++;
 63	}
 64
 65	pages = i;
 66
 67	/*
 68	 * Create a "page actor" which will kmap and kunmap the
 69	 * page cache pages appropriately within the decompressor
 70	 */
 71	actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
 72						start_index << PAGE_SHIFT);
 73	if (actor == NULL)
 74		goto out;
 75
 76	/* Decompress directly into the page cache buffers */
 77	res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
 78
 79	last_page = squashfs_page_actor_free(actor);
 80
 81	if (res < 0)
 82		goto mark_errored;
 83
 84	if (res != expected || IS_ERR(last_page)) {
 85		res = -EIO;
 86		goto mark_errored;
 87	}
 88
 89	/* Last page (if present) may have trailing bytes not filled */
 90	bytes = res % PAGE_SIZE;
 91	if (end_index == file_end && last_page && bytes) {
 92		pageaddr = kmap_local_page(last_page);
 93		memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
 94		kunmap_local(pageaddr);
 95	}
 96
 97	/* Mark pages as uptodate, unlock and release */
 98	for (i = 0; i < pages; i++) {
 99		flush_dcache_page(page[i]);
100		SetPageUptodate(page[i]);
101		unlock_page(page[i]);
102		if (page[i] != target_page)
103			put_page(page[i]);
104	}
105
106	kfree(page);
107
108	return 0;
109
110mark_errored:
111	/* Decompression failed.  Target_page is
112	 * dealt with by the caller
113	 */
114	for (i = 0; i < pages; i++) {
115		if (page[i] == NULL || page[i] == target_page)
116			continue;
117		flush_dcache_page(page[i]);
118		unlock_page(page[i]);
119		put_page(page[i]);
120	}
121
122out:
123	kfree(page);
124	return res;
125}