fs/squashfs/page_actor.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (c) 2013
0004  * Phillip Lougher <phillip@squashfs.org.uk>
0005  */
0006
0007 #include <linux/kernel.h>
0008 #include <linux/slab.h>
0009 #include <linux/pagemap.h>
0010 #include "squashfs_fs_sb.h"
0011 #include "decompressor.h"
0012 #include "page_actor.h"
0013
0014 /*
0015  * This file contains implementations of page_actor for decompressing into
0016  * an intermediate buffer, and for decompressing directly into the
0017  * page cache.
0018  *
0019  * Calling code should avoid sleeping between calls to squashfs_first_page()
0020  * and squashfs_finish_page().
0021  */
0022
0023 /* Implementation of page_actor for decompressing into intermediate buffer */
0024 static void *cache_first_page(struct squashfs_page_actor *actor)
0025 {
0026     actor->next_page = 1;
0027     return actor->buffer[0];
0028 }
0029
0030 static void *cache_next_page(struct squashfs_page_actor *actor)
0031 {
0032     if (actor->next_page == actor->pages)
0033         return NULL;
0034
0035     return actor->buffer[actor->next_page++];
0036 }
0037
0038 static void cache_finish_page(struct squashfs_page_actor *actor)
0039 {
0040     /* empty */
0041 }
0042
0043 struct squashfs_page_actor *squashfs_page_actor_init(void **buffer,
0044     int pages, int length)
0045 {
0046     struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
0047
0048     if (actor == NULL)
0049         return NULL;
0050
0051     actor->length = length ? : pages * PAGE_SIZE;
0052     actor->buffer = buffer;
0053     actor->pages = pages;
0054     actor->next_page = 0;
0055     actor->tmp_buffer = NULL;
0056     actor->squashfs_first_page = cache_first_page;
0057     actor->squashfs_next_page = cache_next_page;
0058     actor->squashfs_finish_page = cache_finish_page;
0059     return actor;
0060 }
0061
0062 /* Implementation of page_actor for decompressing directly into page cache. */
0063 static void *handle_next_page(struct squashfs_page_actor *actor)
0064 {
0065     int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT;
0066
0067     if (actor->returned_pages == max_pages)
0068         return NULL;
0069
0070     if ((actor->next_page == actor->pages) ||
0071             (actor->next_index != actor->page[actor->next_page]->index)) {
0072         actor->next_index++;
0073         actor->returned_pages++;
0074         return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
0075     }
0076
0077     actor->next_index++;
0078     actor->returned_pages++;
0079     return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
0080 }
0081
0082 static void *direct_first_page(struct squashfs_page_actor *actor)
0083 {
0084     return handle_next_page(actor);
0085 }
0086
0087 static void *direct_next_page(struct squashfs_page_actor *actor)
0088 {
0089     if (actor->pageaddr) {
0090         kunmap_local(actor->pageaddr);
0091         actor->pageaddr = NULL;
0092     }
0093
0094     return handle_next_page(actor);
0095 }
0096
0097 static void direct_finish_page(struct squashfs_page_actor *actor)
0098 {
0099     if (actor->pageaddr)
0100         kunmap_local(actor->pageaddr);
0101 }
0102
0103 struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
0104     struct page **page, int pages, int length)
0105 {
0106     struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
0107
0108     if (actor == NULL)
0109         return NULL;
0110
0111     if (msblk->decompressor->alloc_buffer) {
0112         actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
0113
0114         if (actor->tmp_buffer == NULL) {
0115             kfree(actor);
0116             return NULL;
0117         }
0118     } else
0119         actor->tmp_buffer = NULL;
0120
0121     actor->length = length ? : pages * PAGE_SIZE;
0122     actor->page = page;
0123     actor->pages = pages;
0124     actor->next_page = 0;
0125     actor->returned_pages = 0;
0126     actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1);
0127     actor->pageaddr = NULL;
0128     actor->alloc_buffer = msblk->decompressor->alloc_buffer;
0129     actor->squashfs_first_page = direct_first_page;
0130     actor->squashfs_next_page = direct_next_page;
0131     actor->squashfs_finish_page = direct_finish_page;
0132     return actor;
0133 }