source: src/linux/universal/linux-4.9/fs/squashfs/file_direct.c @ 31630

Last change on this file since 31630 was 31630, checked in by brainslayer, 4 months ago

new fs is compatible with standard squashfs, just smaller

File size: 4.3 KB
Line 
1/*
2 * Copyright (c) 2013
3 * Phillip Lougher <phillip@squashfs.org.uk>
4 *
5 * This work is licensed under the terms of the GNU GPL, version 2. See
6 * the COPYING file in the top-level directory.
7 */
8
9#include <linux/fs.h>
10#include <linux/vfs.h>
11#include <linux/kernel.h>
12#include <linux/slab.h>
13#include <linux/string.h>
14#include <linux/pagemap.h>
15#include <linux/mutex.h>
16
17#include "squashfs_fs.h"
18#include "squashfs_fs_sb.h"
19#include "squashfs_fs_i.h"
20#include "squashfs.h"
21#include "page_actor.h"
22
23static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
24        int pages, struct page **page);
25
26/* Read separately compressed datablock directly into page cache */
27int squashfs_readpage_block(struct page *target_page, u64 block, int bsize)
28
29{
30        struct inode *inode = target_page->mapping->host;
31        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
32
33        int file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
34        int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
35        int start_index = target_page->index & ~mask;
36        int end_index = start_index | mask;
37        int i, n, pages, missing_pages, bytes, res = -ENOMEM;
38        struct page **page;
39        struct squashfs_page_actor *actor;
40        void *pageaddr;
41
42        if (end_index > file_end)
43                end_index = file_end;
44
45        pages = end_index - start_index + 1;
46
47        page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
48        if (page == NULL)
49                return res;
50
51        /*
52         * Create a "page actor" which will kmap and kunmap the
53         * page cache pages appropriately within the decompressor
54         */
55        actor = squashfs_page_actor_init_special(page, pages, 0);
56        if (actor == NULL)
57                goto out;
58
59        /* Try to grab all the pages covered by the Squashfs block */
60        for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {
61                page[i] = (n == target_page->index) ? target_page :
62                        grab_cache_page_nowait(target_page->mapping, n);
63
64                if (page[i] == NULL) {
65                        missing_pages++;
66                        continue;
67                }
68
69                if (PageUptodate(page[i])) {
70                        unlock_page(page[i]);
71                        put_page(page[i]);
72                        page[i] = NULL;
73                        missing_pages++;
74                }
75        }
76
77        if (missing_pages) {
78                /*
79                 * Couldn't get one or more pages, this page has either
80                 * been VM reclaimed, but others are still in the page cache
81                 * and uptodate, or we're racing with another thread in
82                 * squashfs_readpage also trying to grab them.  Fall back to
83                 * using an intermediate buffer.
84                 */
85                res = squashfs_read_cache(target_page, block, bsize, pages,
86                                                                page);
87                if (res < 0)
88                        goto mark_errored;
89
90                goto out;
91        }
92
93        /* Decompress directly into the page cache buffers */
94        res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
95        if (res < 0)
96                goto mark_errored;
97
98        /* Last page may have trailing bytes not filled */
99        bytes = res % PAGE_SIZE;
100        if (bytes) {
101                pageaddr = kmap_atomic(page[pages - 1]);
102                memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
103                kunmap_atomic(pageaddr);
104        }
105
106        /* Mark pages as uptodate, unlock and release */
107        for (i = 0; i < pages; i++) {
108                flush_dcache_page(page[i]);
109                SetPageUptodate(page[i]);
110                unlock_page(page[i]);
111                if (page[i] != target_page)
112                        put_page(page[i]);
113        }
114
115        kfree(actor);
116        kfree(page);
117
118        return 0;
119
120mark_errored:
121        /* Decompression failed, mark pages as errored.  Target_page is
122         * dealt with by the caller
123         */
124        for (i = 0; i < pages; i++) {
125                if (page[i] == NULL || page[i] == target_page)
126                        continue;
127                flush_dcache_page(page[i]);
128                SetPageError(page[i]);
129                unlock_page(page[i]);
130                put_page(page[i]);
131        }
132
133out:
134        kfree(actor);
135        kfree(page);
136        return res;
137}
138
139
140static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
141        int pages, struct page **page)
142{
143        struct inode *i = target_page->mapping->host;
144        struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
145                                                 block, bsize);
146        int bytes = buffer->length, res = buffer->error, n, offset = 0;
147        void *pageaddr;
148
149        if (res) {
150                ERROR("Unable to read page, block %llx, size %x\n", block,
151                        bsize);
152                goto out;
153        }
154
155        for (n = 0; n < pages && bytes > 0; n++,
156                        bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
157                int avail = min_t(int, bytes, PAGE_SIZE);
158
159                if (page[n] == NULL)
160                        continue;
161
162                pageaddr = kmap_atomic(page[n]);
163                squashfs_copy_data(pageaddr, buffer, offset, avail);
164                memset(pageaddr + avail, 0, PAGE_SIZE - avail);
165                kunmap_atomic(pageaddr);
166                flush_dcache_page(page[n]);
167                SetPageUptodate(page[n]);
168                unlock_page(page[n]);
169                if (page[n] != target_page)
170                        put_page(page[n]);
171        }
172
173out:
174        squashfs_cache_put(buffer);
175        return res;
176}
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