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 */ 22 int 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; 107 108 mark_errored: 109 /* Decompression failed. 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 unlock_page(page[i]); 117 put_page(page[i]); 118 } 119 120 out: 121 kfree(page); 122 return res; 123 } 124