Commit 1dc4bba39dd29c6d6f77ca7bf63cd3adeb6fc162
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Squashfs: symlink operations
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Showing 1 changed file with 118 additions and 0 deletions Side-by-side Diff
fs/squashfs/symlink.c
| 1 | +/* | |
| 2 | + * Squashfs - a compressed read only filesystem for Linux | |
| 3 | + * | |
| 4 | + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 | |
| 5 | + * Phillip Lougher <phillip@lougher.demon.co.uk> | |
| 6 | + * | |
| 7 | + * This program is free software; you can redistribute it and/or | |
| 8 | + * modify it under the terms of the GNU General Public License | |
| 9 | + * as published by the Free Software Foundation; either version 2, | |
| 10 | + * or (at your option) any later version. | |
| 11 | + * | |
| 12 | + * This program is distributed in the hope that it will be useful, | |
| 13 | + * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 14 | + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 15 | + * GNU General Public License for more details. | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License | |
| 18 | + * along with this program; if not, write to the Free Software | |
| 19 | + * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
| 20 | + * | |
| 21 | + * symlink.c | |
| 22 | + */ | |
| 23 | + | |
| 24 | +/* | |
| 25 | + * This file implements code to handle symbolic links. | |
| 26 | + * | |
| 27 | + * The data contents of symbolic links are stored inside the symbolic | |
| 28 | + * link inode within the inode table. This allows the normally small symbolic | |
| 29 | + * link to be compressed as part of the inode table, achieving much greater | |
| 30 | + * compression than if the symbolic link was compressed individually. | |
| 31 | + */ | |
| 32 | + | |
| 33 | +#include <linux/fs.h> | |
| 34 | +#include <linux/vfs.h> | |
| 35 | +#include <linux/kernel.h> | |
| 36 | +#include <linux/slab.h> | |
| 37 | +#include <linux/string.h> | |
| 38 | +#include <linux/pagemap.h> | |
| 39 | +#include <linux/zlib.h> | |
| 40 | + | |
| 41 | +#include "squashfs_fs.h" | |
| 42 | +#include "squashfs_fs_sb.h" | |
| 43 | +#include "squashfs_fs_i.h" | |
| 44 | +#include "squashfs.h" | |
| 45 | + | |
| 46 | +static int squashfs_symlink_readpage(struct file *file, struct page *page) | |
| 47 | +{ | |
| 48 | + struct inode *inode = page->mapping->host; | |
| 49 | + struct super_block *sb = inode->i_sb; | |
| 50 | + struct squashfs_sb_info *msblk = sb->s_fs_info; | |
| 51 | + int index = page->index << PAGE_CACHE_SHIFT; | |
| 52 | + u64 block = squashfs_i(inode)->start; | |
| 53 | + int offset = squashfs_i(inode)->offset; | |
| 54 | + int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE); | |
| 55 | + int bytes, copied; | |
| 56 | + void *pageaddr; | |
| 57 | + struct squashfs_cache_entry *entry; | |
| 58 | + | |
| 59 | + TRACE("Entered squashfs_symlink_readpage, page index %ld, start block " | |
| 60 | + "%llx, offset %x\n", page->index, block, offset); | |
| 61 | + | |
| 62 | + /* | |
| 63 | + * Skip index bytes into symlink metadata. | |
| 64 | + */ | |
| 65 | + if (index) { | |
| 66 | + bytes = squashfs_read_metadata(sb, NULL, &block, &offset, | |
| 67 | + index); | |
| 68 | + if (bytes < 0) { | |
| 69 | + ERROR("Unable to read symlink [%llx:%x]\n", | |
| 70 | + squashfs_i(inode)->start, | |
| 71 | + squashfs_i(inode)->offset); | |
| 72 | + goto error_out; | |
| 73 | + } | |
| 74 | + } | |
| 75 | + | |
| 76 | + /* | |
| 77 | + * Read length bytes from symlink metadata. Squashfs_read_metadata | |
| 78 | + * is not used here because it can sleep and we want to use | |
| 79 | + * kmap_atomic to map the page. Instead call the underlying | |
| 80 | + * squashfs_cache_get routine. As length bytes may overlap metadata | |
| 81 | + * blocks, we may need to call squashfs_cache_get multiple times. | |
| 82 | + */ | |
| 83 | + for (bytes = 0; bytes < length; offset = 0, bytes += copied) { | |
| 84 | + entry = squashfs_cache_get(sb, msblk->block_cache, block, 0); | |
| 85 | + if (entry->error) { | |
| 86 | + ERROR("Unable to read symlink [%llx:%x]\n", | |
| 87 | + squashfs_i(inode)->start, | |
| 88 | + squashfs_i(inode)->offset); | |
| 89 | + squashfs_cache_put(entry); | |
| 90 | + goto error_out; | |
| 91 | + } | |
| 92 | + | |
| 93 | + pageaddr = kmap_atomic(page, KM_USER0); | |
| 94 | + copied = squashfs_copy_data(pageaddr + bytes, entry, offset, | |
| 95 | + length - bytes); | |
| 96 | + if (copied == length - bytes) | |
| 97 | + memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length); | |
| 98 | + else | |
| 99 | + block = entry->next_index; | |
| 100 | + kunmap_atomic(pageaddr, KM_USER0); | |
| 101 | + squashfs_cache_put(entry); | |
| 102 | + } | |
| 103 | + | |
| 104 | + flush_dcache_page(page); | |
| 105 | + SetPageUptodate(page); | |
| 106 | + unlock_page(page); | |
| 107 | + return 0; | |
| 108 | + | |
| 109 | +error_out: | |
| 110 | + SetPageError(page); | |
| 111 | + unlock_page(page); | |
| 112 | + return 0; | |
| 113 | +} | |
| 114 | + | |
| 115 | + | |
| 116 | +const struct address_space_operations squashfs_symlink_aops = { | |
| 117 | + .readpage = squashfs_symlink_readpage | |
| 118 | +}; |