LXR linux/fs/squashfs/file

   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/fs.h>
   8#include <linux/vfs.h>
   9#include <linux/kernel.h>
  10#include <linux/slab.h>
  11#include <linux/string.h>
  12#include <linux/pagemap.h>
  13#include <linux/mutex.h>
  14
  15#include "squashfs_fs.h"
  16#include "squashfs_fs_sb.h"
  17#include "squashfs_fs_i.h"
  18#include "squashfs.h"
  19#include "page_actor.h"
  20
  21static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
  22        int pages, struct page **page, int bytes);
  23
  24/* Read separately compressed datablock directly into page cache */
  25int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
  26        int expected)
  27
  28{
  29        struct inode *inode = target_page->mapping->host;
  30        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
  31
  32        int file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
  33        int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
  34        int start_index = target_page->index & ~mask;
  35        int end_index = start_index | mask;
  36        int i, n, pages, missing_pages, bytes, res = -ENOMEM;
  37        struct page **page;
  38        struct squashfs_page_actor *actor;
  39        void *pageaddr;
  40
  41        if (end_index > file_end)
  42                end_index = file_end;
  43
  44        pages = end_index - start_index + 1;
  45
  46        page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
  47        if (page == NULL)
  48                return res;
  49
  50        /*
  51         * Create a "page actor" which will kmap and kunmap the
  52         * page cache pages appropriately within the decompressor
  53         */
  54        actor = squashfs_page_actor_init_special(page, pages, 0);
  55        if (actor == NULL)
  56                goto out;
  57
  58        /* Try to grab all the pages covered by the Squashfs block */
  59        for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {
  60                page[i] = (n == target_page->index) ? target_page :
  61                        grab_cache_page_nowait(target_page->mapping, n);
  62
  63                if (page[i] == NULL) {
  64                        missing_pages++;
  65                        continue;
  66                }
  67
  68                if (PageUptodate(page[i])) {
  69                        unlock_page(page[i]);
  70                        put_page(page[i]);
  71                        page[i] = NULL;
  72                        missing_pages++;
  73                }
  74        }
  75
  76        if (missing_pages) {
  77                /*
  78                 * Couldn't get one or more pages, this page has either
  79                 * been VM reclaimed, but others are still in the page cache
  80                 * and uptodate, or we're racing with another thread in
  81                 * squashfs_readpage also trying to grab them.  Fall back to
  82                 * using an intermediate buffer.
  83                 */
  84                res = squashfs_read_cache(target_page, block, bsize, pages,
  85                                                        page, expected);
  86                if (res < 0)
  87                        goto mark_errored;
  88
  89                goto out;
  90        }
  91
  92        /* Decompress directly into the page cache buffers */
  93        res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
  94        if (res < 0)
  95                goto mark_errored;
  96
  97        if (res != expected) {
  98                res = -EIO;
  99                goto mark_errored;
 100        }
 101
 102        /* Last page may have trailing bytes not filled */
 103        bytes = res % PAGE_SIZE;
 104        if (bytes) {
 105                pageaddr = kmap_atomic(page[pages - 1]);
 106                memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
 107                kunmap_atomic(pageaddr);
 108        }
 109
 110        /* Mark pages as uptodate, unlock and release */
 111        for (i = 0; i < pages; i++) {
 112                flush_dcache_page(page[i]);
 113                SetPageUptodate(page[i]);
 114                unlock_page(page[i]);
 115                if (page[i] != target_page)
 116                        put_page(page[i]);
 117        }
 118
 119        kfree(actor);
 120        kfree(page);
 121
 122        return 0;
 123
 124mark_errored:
 125        /* Decompression failed, mark pages as errored.  Target_page is
 126         * dealt with by the caller
 127         */
 128        for (i = 0; i < pages; i++) {
 129                if (page[i] == NULL || page[i] == target_page)
 130                        continue;
 131                flush_dcache_page(page[i]);
 132                SetPageError(page[i]);
 133                unlock_page(page[i]);
 134                put_page(page[i]);
 135        }
 136
 137out:
 138        kfree(actor);
 139        kfree(page);
 140        return res;
 141}
 142
 143
 144static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
 145        int pages, struct page **page, int bytes)
 146{
 147        struct inode *i = target_page->mapping->host;
 148        struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
 149                                                 block, bsize);
 150        int res = buffer->error, n, offset = 0;
 151
 152        if (res) {
 153                ERROR("Unable to read page, block %llx, size %x\n", block,
 154                        bsize);
 155                goto out;
 156        }
 157
 158        for (n = 0; n < pages && bytes > 0; n++,
 159                        bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
 160                int avail = min_t(int, bytes, PAGE_SIZE);
 161
 162                if (page[n] == NULL)
 163                        continue;
 164
 165                squashfs_fill_page(page[n], buffer, offset, avail);
 166                unlock_page(page[n]);
 167                if (page[n] != target_page)
 168                        put_page(page[n]);
 169        }
 170
 171out:
 172        squashfs_cache_put(buffer);
 173        return res;
 174}
 175