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 "page_actor.h" 11 12 /* 13 * This file contains implementations of page_actor for decompressing into 14 * an intermediate buffer, and for decompressing directly into the 15 * page cache. 16 * 17 * Calling code should avoid sleeping between calls to squashfs_first_page() 18 * and squashfs_finish_page(). 19 */ 20 21 /* Implementation of page_actor for decompressing into intermediate buffer */ 22 static void *cache_first_page(struct squashfs_page_actor *actor) 23 { 24 actor->next_page = 1; 25 return actor->buffer[0]; 26 } 27 28 static void *cache_next_page(struct squashfs_page_actor *actor) 29 { 30 if (actor->next_page == actor->pages) 31 return NULL; 32 33 return actor->buffer[actor->next_page++]; 34 } 35 36 static void cache_finish_page(struct squashfs_page_actor *actor) 37 { 38 /* empty */ 39 } 40 41 struct squashfs_page_actor *squashfs_page_actor_init(void **buffer, 42 int pages, int length) 43 { 44 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL); 45 46 if (actor == NULL) 47 return NULL; 48 49 actor->length = length ? : pages * PAGE_SIZE; 50 actor->buffer = buffer; 51 actor->pages = pages; 52 actor->next_page = 0; 53 actor->squashfs_first_page = cache_first_page; 54 actor->squashfs_next_page = cache_next_page; 55 actor->squashfs_finish_page = cache_finish_page; 56 return actor; 57 } 58 59 /* Implementation of page_actor for decompressing directly into page cache. */ 60 static void *direct_first_page(struct squashfs_page_actor *actor) 61 { 62 actor->next_page = 1; 63 return actor->pageaddr = kmap_atomic(actor->page[0]); 64 } 65 66 static void *direct_next_page(struct squashfs_page_actor *actor) 67 { 68 if (actor->pageaddr) 69 kunmap_atomic(actor->pageaddr); 70 71 return actor->pageaddr = actor->next_page == actor->pages ? NULL : 72 kmap_atomic(actor->page[actor->next_page++]); 73 } 74 75 static void direct_finish_page(struct squashfs_page_actor *actor) 76 { 77 if (actor->pageaddr) 78 kunmap_atomic(actor->pageaddr); 79 } 80 81 struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page, 82 int pages, int length) 83 { 84 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL); 85 86 if (actor == NULL) 87 return NULL; 88 89 actor->length = length ? : pages * PAGE_SIZE; 90 actor->page = page; 91 actor->pages = pages; 92 actor->next_page = 0; 93 actor->pageaddr = NULL; 94 actor->squashfs_first_page = direct_first_page; 95 actor->squashfs_next_page = direct_next_page; 96 actor->squashfs_finish_page = direct_finish_page; 97 return actor; 98 } 99