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