fs/squashfs/page_actor.c

   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 }