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/kernel.h> 10 #include <linux/slab.h> 11 #include <linux/pagemap.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 *direct_first_page(struct squashfs_page_actor *actor) 63 { 64 actor->next_page = 1; 65 return actor->pageaddr = kmap_atomic(actor->page[0]); 66 } 67 68 static void *direct_next_page(struct squashfs_page_actor *actor) 69 { 70 if (actor->pageaddr) 71 kunmap_atomic(actor->pageaddr); 72 73 return actor->pageaddr = actor->next_page == actor->pages ? NULL : 74 kmap_atomic(actor->page[actor->next_page++]); 75 } 76 77 static void direct_finish_page(struct squashfs_page_actor *actor) 78 { 79 if (actor->pageaddr) 80 kunmap_atomic(actor->pageaddr); 81 } 82 83 struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page, 84 int pages, int length) 85 { 86 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL); 87 88 if (actor == NULL) 89 return NULL; 90 91 actor->length = length ? : pages * PAGE_SIZE; 92 actor->page = page; 93 actor->pages = pages; 94 actor->next_page = 0; 95 actor->pageaddr = NULL; 96 actor->squashfs_first_page = direct_first_page; 97 actor->squashfs_next_page = direct_next_page; 98 actor->squashfs_finish_page = direct_finish_page; 99 return actor; 100 } 101