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 inode *inode = target_page->mapping->host;
27	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
28
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 = target_page->index & ~mask;
32	loff_t end_index = start_index | mask;
33	int i, n, pages, bytes, res = -ENOMEM;
34	struct page **page;
35	struct squashfs_page_actor *actor;
36	void *pageaddr;
37
38	if (end_index > file_end)
39		end_index = file_end;
40
41	pages = end_index - start_index + 1;
42
43	page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
44	if (page == NULL)
45		return res;
46
47	/* Try to grab all the pages covered by the Squashfs block */
48	for (i = 0, n = start_index; n <= end_index; n++) {
49		page[i] = (n == target_page->index) ? target_page :
50			grab_cache_page_nowait(target_page->mapping, n);
51
52		if (page[i] == NULL)
53			continue;
54
55		if (PageUptodate(page[i])) {
56			unlock_page(page[i]);
57			put_page(page[i]);
58			continue;
59		}
60
61		i++;
62	}
63
64	pages = i;
65
66	/*
67	 * Create a "page actor" which will kmap and kunmap the
68	 * page cache pages appropriately within the decompressor
69	 */
70	actor = squashfs_page_actor_init_special(msblk, page, pages, expected);
71	if (actor == NULL)
72		goto out;
73
74	/* Decompress directly into the page cache buffers */
75	res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
76
77	squashfs_page_actor_free(actor);
78
79	if (res < 0)
80		goto mark_errored;
81
82	if (res != expected) {
83		res = -EIO;
84		goto mark_errored;
85	}
86
87	/* Last page (if present) may have trailing bytes not filled */
88	bytes = res % PAGE_SIZE;
89	if (page[pages - 1]->index == end_index && bytes) {
90		pageaddr = kmap_local_page(page[pages - 1]);
91		memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
92		kunmap_local(pageaddr);
93	}
94
95	/* Mark pages as uptodate, unlock and release */
96	for (i = 0; i < pages; i++) {
97		flush_dcache_page(page[i]);
98		SetPageUptodate(page[i]);
99		unlock_page(page[i]);
100		if (page[i] != target_page)
101			put_page(page[i]);
102	}
103
104	kfree(page);
105
106	return 0;
107
108mark_errored:
109	/* Decompression failed, mark pages as errored.  Target_page is
110	 * dealt with by the caller
111	 */
112	for (i = 0; i < pages; i++) {
113		if (page[i] == NULL || page[i] == target_page)
114			continue;
115		flush_dcache_page(page[i]);
116		SetPageError(page[i]);
117		unlock_page(page[i]);
118		put_page(page[i]);
119	}
120
121out:
122	kfree(page);
123	return res;
124}
125