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 page *target_page, u64 block, int bsize,
  23         int expected)
  24
  25 {
  26         struct folio *folio = page_folio(target_page);
  27         struct inode *inode = target_page->mapping->host;
  28         struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
  29         loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
  30         int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
  31         loff_t start_index = folio->index & ~mask;
  32         loff_t end_index = start_index | mask;
  33         loff_t index;
  34         int i, pages, bytes, res = -ENOMEM;
  35         struct page **page, *last_page;
  36         struct squashfs_page_actor *actor;
  37         void *pageaddr;
  38
  39         if (end_index > file_end)
  40                 end_index = file_end;
  41
  42         pages = end_index - start_index + 1;
  43
  44         page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
  45         if (page == NULL)
  46                 return res;
  47
  48         /* Try to grab all the pages covered by the Squashfs block */
  49         for (i = 0, index = start_index; index <= end_index; index++) {
  50                 page[i] = (index == folio->index) ? target_page :
  51                         grab_cache_page_nowait(target_page->mapping, index);
  52
  53                 if (page[i] == NULL)
  54                         continue;
  55
  56                 if (PageUptodate(page[i])) {
  57                         unlock_page(page[i]);
  58                         put_page(page[i]);
  59                         continue;
  60                 }
  61
  62                 i++;
  63         }
  64
  65         pages = i;
  66
  67         /*
  68          * Create a "page actor" which will kmap and kunmap the
  69          * page cache pages appropriately within the decompressor
  70          */
  71         actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
  72                                                 start_index << PAGE_SHIFT);
  73         if (actor == NULL)
  74                 goto out;
  75
  76         /* Decompress directly into the page cache buffers */
  77         res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
  78
  79         last_page = squashfs_page_actor_free(actor);
  80
  81         if (res < 0)
  82                 goto mark_errored;
  83
  84         if (res != expected || IS_ERR(last_page)) {
  85                 res = -EIO;
  86                 goto mark_errored;
  87         }
  88
  89         /* Last page (if present) may have trailing bytes not filled */
  90         bytes = res % PAGE_SIZE;
  91         if (end_index == file_end && last_page && bytes) {
  92                 pageaddr = kmap_local_page(last_page);
  93                 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
  94                 kunmap_local(pageaddr);
  95         }
  96
  97         /* Mark pages as uptodate, unlock and release */
  98         for (i = 0; i < pages; i++) {
  99                 flush_dcache_page(page[i]);
 100                 SetPageUptodate(page[i]);
 101                 unlock_page(page[i]);
 102                 if (page[i] != target_page)
 103                         put_page(page[i]);
 104         }
 105
 106         kfree(page);
 107
 108         return 0;
 109
 110 mark_errored:
 111         /* Decompression failed.  Target_page is
 112          * dealt with by the caller
 113          */
 114         for (i = 0; i < pages; i++) {
 115                 if (page[i] == NULL || page[i] == target_page)
 116                         continue;
 117                 flush_dcache_page(page[i]);
 118                 unlock_page(page[i]);
 119                 put_page(page[i]);
 120         }
 121
 122 out:
 123         kfree(page);
 124         return res;
 125 }