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/kernel.h> 8 #include <linux/slab.h> 9 #include <linux/pagemap.h> 10 #include "squashfs_fs_sb.h" 11 #include "decompressor.h" 12 #include "page_actor.h" 13 14 /* 15 * This file contains implementations of page_actor for decompressing into 16 * an intermediate buffer, and for decompressing directly into the 17 * page cache. 18 * 19 * Calling code should avoid sleeping between calls to squashfs_first_page() 20 * and squashfs_finish_page(). 21 */ 22 23 /* Implementation of page_actor for decompressing into intermediate buffer */ 24 static void *cache_first_page(struct squashfs_page_actor *actor) 25 { 26 actor->next_page = 1; 27 return actor->buffer[0]; 28 } 29 30 static void *cache_next_page(struct squashfs_page_actor *actor) 31 { 32 if (actor->next_page == actor->pages) 33 return NULL; 34 35 return actor->buffer[actor->next_page++]; 36 } 37 38 static void cache_finish_page(struct squashfs_page_actor *actor) 39 { 40 /* empty */ 41 } 42 43 struct squashfs_page_actor *squashfs_page_actor_init(void **buffer, 44 int pages, int length) 45 { 46 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL); 47 48 if (actor == NULL) 49 return NULL; 50 51 actor->length = length ? : pages * PAGE_SIZE; 52 actor->buffer = buffer; 53 actor->pages = pages; 54 actor->next_page = 0; 55 actor->squashfs_first_page = cache_first_page; 56 actor->squashfs_next_page = cache_next_page; 57 actor->squashfs_finish_page = cache_finish_page; 58 return actor; 59 } 60 61 /* Implementation of page_actor for decompressing directly into page cache. */ 62 static void *handle_next_page(struct squashfs_page_actor *actor) 63 { 64 int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT; 65 66 if (actor->returned_pages == max_pages) 67 return NULL; 68 69 if ((actor->next_page == actor->pages) || 70 (actor->next_index != actor->page[actor->next_page]->index)) { 71 if (actor->alloc_buffer) { 72 void *tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL); 73 74 if (tmp_buffer) { 75 actor->tmp_buffer = tmp_buffer; 76 actor->next_index++; 77 actor->returned_pages++; 78 return tmp_buffer; 79 } 80 } 81 82 actor->next_index++; 83 actor->returned_pages++; 84 return ERR_PTR(-ENOMEM); 85 } 86 87 actor->next_index++; 88 actor->returned_pages++; 89 return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]); 90 } 91 92 static void *direct_first_page(struct squashfs_page_actor *actor) 93 { 94 return handle_next_page(actor); 95 } 96 97 static void *direct_next_page(struct squashfs_page_actor *actor) 98 { 99 if (actor->pageaddr) 100 kunmap_local(actor->pageaddr); 101 102 kfree(actor->tmp_buffer); 103 actor->pageaddr = actor->tmp_buffer = NULL; 104 105 return handle_next_page(actor); 106 } 107 108 static void direct_finish_page(struct squashfs_page_actor *actor) 109 { 110 if (actor->pageaddr) 111 kunmap_local(actor->pageaddr); 112 113 kfree(actor->tmp_buffer); 114 } 115 116 struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk, 117 struct page **page, int pages, int length) 118 { 119 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL); 120 121 if (actor == NULL) 122 return NULL; 123 124 actor->length = length ? : pages * PAGE_SIZE; 125 actor->page = page; 126 actor->pages = pages; 127 actor->next_page = 0; 128 actor->returned_pages = 0; 129 actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1); 130 actor->pageaddr = NULL; 131 actor->tmp_buffer = NULL; 132 actor->alloc_buffer = msblk->decompressor->alloc_buffer; 133 actor->squashfs_first_page = direct_first_page; 134 actor->squashfs_next_page = direct_next_page; 135 actor->squashfs_finish_page = direct_finish_page; 136 return actor; 137 } 138