fs/squashfs/file_direct.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/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
  21 /* Read separately compressed datablock directly into page cache */
  22 int squashfs_readpage_block(struct folio *folio, u64 block, int bsize,
  23                 int expected)
  24 {
  25         struct page *target_page = &folio->page;
  26         struct inode *inode = folio->mapping->host;
  27         struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
  28         loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
  29         int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
  30         loff_t start_index = folio->index & ~mask;
  31         loff_t end_index = start_index | mask;
  32         loff_t index;
  33         int i, pages, bytes, res = -ENOMEM;
  34         struct page **page, *last_page;
  35         struct squashfs_page_actor *actor;
  36         void *pageaddr;
  37
  38         if (end_index > file_end)
  39                 end_index = file_end;
  40
  41         pages = end_index - start_index + 1;
  42
  43         page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
  44         if (page == NULL)
  45                 return res;
  46
  47         /* Try to grab all the pages covered by the Squashfs block */
  48         for (i = 0, index = start_index; index <= end_index; index++) {
  49                 page[i] = (index == folio->index) ? target_page :
  50                         grab_cache_page_nowait(folio->mapping, index);
  51
  52                 if (page[i] == NULL)
  53                         continue;
  54
  55                 if (PageUptodate(page[i])) {
  56                         unlock_page(page[i]);
  57                         put_page(page[i]);
  58                         continue;
  59                 }
  60
  61                 i++;
  62         }
  63
  64         pages = i;
  65
  66         /*
  67          * Create a "page actor" which will kmap and kunmap the
  68          * page cache pages appropriately within the decompressor
  69          */
  70         actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
  71                                                 start_index << PAGE_SHIFT);
  72         if (actor == NULL)
  73                 goto out;
  74
  75         /* Decompress directly into the page cache buffers */
  76         res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
  77
  78         last_page = squashfs_page_actor_free(actor);
  79
  80         if (res < 0)
  81                 goto mark_errored;
  82
  83         if (res != expected || IS_ERR(last_page)) {
  84                 res = -EIO;
  85                 goto mark_errored;
  86         }
  87
  88         /* Last page (if present) may have trailing bytes not filled */
  89         bytes = res % PAGE_SIZE;
  90         if (end_index == file_end && last_page && bytes) {
  91                 pageaddr = kmap_local_page(last_page);
  92                 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
  93                 kunmap_local(pageaddr);
  94         }
  95
  96         /* Mark pages as uptodate, unlock and release */
  97         for (i = 0; i < pages; i++) {
  98                 flush_dcache_page(page[i]);
  99                 SetPageUptodate(page[i]);
 100                 unlock_page(page[i]);
 101                 if (page[i] != target_page)
 102                         put_page(page[i]);
 103         }
 104
 105         kfree(page);
 106
 107         return 0;
 108
 109 mark_errored:
 110         /* Decompression failed.  Target_page is
 111          * dealt with by the caller
 112          */
 113         for (i = 0; i < pages; i++) {
 114                 if (page[i] == NULL || page[i] == target_page)
 115                         continue;
 116                 flush_dcache_page(page[i]);
 117                 unlock_page(page[i]);
 118                 put_page(page[i]);
 119         }
 120
 121 out:
 122         kfree(page);
 123         return res;
 124 }