fs/squashfs/page_actor.c

   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->tmp_buffer = NULL;
  56         actor->squashfs_first_page = cache_first_page;
  57         actor->squashfs_next_page = cache_next_page;
  58         actor->squashfs_finish_page = cache_finish_page;
  59         return actor;
  60 }
  61
  62 /* Implementation of page_actor for decompressing directly into page cache. */
  63 static void *handle_next_page(struct squashfs_page_actor *actor)
  64 {
  65         int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT;
  66
  67         if (actor->returned_pages == max_pages)
  68                 return NULL;
  69
  70         if ((actor->next_page == actor->pages) ||
  71                         (actor->next_index != actor->page[actor->next_page]->index)) {
  72                 actor->next_index++;
  73                 actor->returned_pages++;
  74                 return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
  75         }
  76
  77         actor->next_index++;
  78         actor->returned_pages++;
  79         return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
  80 }
  81
  82 static void *direct_first_page(struct squashfs_page_actor *actor)
  83 {
  84         return handle_next_page(actor);
  85 }
  86
  87 static void *direct_next_page(struct squashfs_page_actor *actor)
  88 {
  89         if (actor->pageaddr) {
  90                 kunmap_local(actor->pageaddr);
  91                 actor->pageaddr = NULL;
  92         }
  93
  94         return handle_next_page(actor);
  95 }
  96
  97 static void direct_finish_page(struct squashfs_page_actor *actor)
  98 {
  99         if (actor->pageaddr)
 100                 kunmap_local(actor->pageaddr);
 101 }
 102
 103 struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
 104         struct page **page, int pages, int length)
 105 {
 106         struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
 107
 108         if (actor == NULL)
 109                 return NULL;
 110
 111         if (msblk->decompressor->alloc_buffer) {
 112                 actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
 113
 114                 if (actor->tmp_buffer == NULL) {
 115                         kfree(actor);
 116                         return NULL;
 117                 }
 118         } else
 119                 actor->tmp_buffer = NULL;
 120
 121         actor->length = length ? : pages * PAGE_SIZE;
 122         actor->page = page;
 123         actor->pages = pages;
 124         actor->next_page = 0;
 125         actor->returned_pages = 0;
 126         actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1);
 127         actor->pageaddr = NULL;
 128         actor->alloc_buffer = msblk->decompressor->alloc_buffer;
 129         actor->squashfs_first_page = direct_first_page;
 130         actor->squashfs_next_page = direct_next_page;
 131         actor->squashfs_finish_page = direct_finish_page;
 132         return actor;
 133 }