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); 25 26 /* Read separately compressed datablock directly into page cache */ 27 int 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_CACHE_SHIFT; 34 int mask = (1 << (msblk->block_log - PAGE_CACHE_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 page_cache_release(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_CACHE_SIZE; 100 if (bytes) { 101 pageaddr = kmap_atomic(page[pages - 1]); 102 memset(pageaddr + bytes, 0, PAGE_CACHE_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 page_cache_release(page[i]); 113 } 114 115 kfree(actor); 116 kfree(page); 117 118 return 0; 119 120 mark_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 page_cache_release(page[i]); 131 } 132 133 out: 134 kfree(actor); 135 kfree(page); 136 return res; 137 } 138 139 140 static 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_CACHE_SIZE, offset += PAGE_CACHE_SIZE) { 157 int avail = min_t(int, bytes, PAGE_CACHE_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_CACHE_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 page_cache_release(page[n]); 171 } 172 173 out: 174 squashfs_cache_put(buffer); 175 return res; 176 } 177