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 23 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, 24 int pages, struct page **page, int bytes); 25 26 /* Read separately compressed datablock directly into page cache */ 27 int squashfs_readpage_block(struct page *target_page, u64 block, int bsize, 28 int expected) 29 30 { 31 struct inode *inode = target_page->mapping->host; 32 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; 33 34 int file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT; 35 int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1; 36 int start_index = target_page->index & ~mask; 37 int end_index = start_index | mask; 38 int i, n, pages, missing_pages, bytes, res = -ENOMEM; 39 struct page **page; 40 struct squashfs_page_actor *actor; 41 void *pageaddr; 42 43 if (end_index > file_end) 44 end_index = file_end; 45 46 pages = end_index - start_index + 1; 47 48 page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL); 49 if (page == NULL) 50 return res; 51 52 /* 53 * Create a "page actor" which will kmap and kunmap the 54 * page cache pages appropriately within the decompressor 55 */ 56 actor = squashfs_page_actor_init_special(page, pages, 0); 57 if (actor == NULL) 58 goto out; 59 60 /* Try to grab all the pages covered by the Squashfs block */ 61 for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) { 62 page[i] = (n == target_page->index) ? target_page : 63 grab_cache_page_nowait(target_page->mapping, n); 64 65 if (page[i] == NULL) { 66 missing_pages++; 67 continue; 68 } 69 70 if (PageUptodate(page[i])) { 71 unlock_page(page[i]); 72 put_page(page[i]); 73 page[i] = NULL; 74 missing_pages++; 75 } 76 } 77 78 if (missing_pages) { 79 /* 80 * Couldn't get one or more pages, this page has either 81 * been VM reclaimed, but others are still in the page cache 82 * and uptodate, or we're racing with another thread in 83 * squashfs_readpage also trying to grab them. Fall back to 84 * using an intermediate buffer. 85 */ 86 res = squashfs_read_cache(target_page, block, bsize, pages, 87 page, expected); 88 if (res < 0) 89 goto mark_errored; 90 91 goto out; 92 } 93 94 /* Decompress directly into the page cache buffers */ 95 res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor); 96 if (res < 0) 97 goto mark_errored; 98 99 if (res != expected) { 100 res = -EIO; 101 goto mark_errored; 102 } 103 104 /* Last page may have trailing bytes not filled */ 105 bytes = res % PAGE_SIZE; 106 if (bytes) { 107 pageaddr = kmap_atomic(page[pages - 1]); 108 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes); 109 kunmap_atomic(pageaddr); 110 } 111 112 /* Mark pages as uptodate, unlock and release */ 113 for (i = 0; i < pages; i++) { 114 flush_dcache_page(page[i]); 115 SetPageUptodate(page[i]); 116 unlock_page(page[i]); 117 if (page[i] != target_page) 118 put_page(page[i]); 119 } 120 121 kfree(actor); 122 kfree(page); 123 124 return 0; 125 126 mark_errored: 127 /* Decompression failed, mark pages as errored. Target_page is 128 * dealt with by the caller 129 */ 130 for (i = 0; i < pages; i++) { 131 if (page[i] == NULL || page[i] == target_page) 132 continue; 133 flush_dcache_page(page[i]); 134 SetPageError(page[i]); 135 unlock_page(page[i]); 136 put_page(page[i]); 137 } 138 139 out: 140 kfree(actor); 141 kfree(page); 142 return res; 143 } 144 145 146 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize, 147 int pages, struct page **page, int bytes) 148 { 149 struct inode *i = target_page->mapping->host; 150 struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb, 151 block, bsize); 152 int res = buffer->error, n, offset = 0; 153 154 if (res) { 155 ERROR("Unable to read page, block %llx, size %x\n", block, 156 bsize); 157 goto out; 158 } 159 160 for (n = 0; n < pages && bytes > 0; n++, 161 bytes -= PAGE_SIZE, offset += PAGE_SIZE) { 162 int avail = min_t(int, bytes, PAGE_SIZE); 163 164 if (page[n] == NULL) 165 continue; 166 167 squashfs_fill_page(page[n], buffer, offset, avail); 168 unlock_page(page[n]); 169 if (page[n] != target_page) 170 put_page(page[n]); 171 } 172 173 out: 174 squashfs_cache_put(buffer); 175 return res; 176 } 177