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| -rw-r--r-- | fs/squashfs/symlink.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/fs/squashfs/symlink.c b/fs/squashfs/symlink.c new file mode 100644 index 000000000000..83d87880aac8 --- /dev/null +++ b/fs/squashfs/symlink.c @@ -0,0 +1,118 @@ +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher <phillip@lougher.demon.co.uk> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2, + * or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + * symlink.c + */ + +/* + * This file implements code to handle symbolic links. + * + * The data contents of symbolic links are stored inside the symbolic + * link inode within the inode table. This allows the normally small symbolic + * link to be compressed as part of the inode table, achieving much greater + * compression than if the symbolic link was compressed individually. + */ + +#include <linux/fs.h> +#include <linux/vfs.h> +#include <linux/kernel.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/pagemap.h> +#include <linux/zlib.h> + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs_fs_i.h" +#include "squashfs.h" + +static int squashfs_symlink_readpage(struct file *file, struct page *page) +{ + struct inode *inode = page->mapping->host; + struct super_block *sb = inode->i_sb; + struct squashfs_sb_info *msblk = sb->s_fs_info; + int index = page->index << PAGE_CACHE_SHIFT; + u64 block = squashfs_i(inode)->start; + int offset = squashfs_i(inode)->offset; + int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE); + int bytes, copied; + void *pageaddr; + struct squashfs_cache_entry *entry; + + TRACE("Entered squashfs_symlink_readpage, page index %ld, start block " + "%llx, offset %x\n", page->index, block, offset); + + /* + * Skip index bytes into symlink metadata. + */ + if (index) { + bytes = squashfs_read_metadata(sb, NULL, &block, &offset, + index); + if (bytes < 0) { + ERROR("Unable to read symlink [%llx:%x]\n", + squashfs_i(inode)->start, + squashfs_i(inode)->offset); + goto error_out; + } + } + + /* + * Read length bytes from symlink metadata. Squashfs_read_metadata + * is not used here because it can sleep and we want to use + * kmap_atomic to map the page. Instead call the underlying + * squashfs_cache_get routine. As length bytes may overlap metadata + * blocks, we may need to call squashfs_cache_get multiple times. + */ + for (bytes = 0; bytes < length; offset = 0, bytes += copied) { + entry = squashfs_cache_get(sb, msblk->block_cache, block, 0); + if (entry->error) { + ERROR("Unable to read symlink [%llx:%x]\n", + squashfs_i(inode)->start, + squashfs_i(inode)->offset); + squashfs_cache_put(entry); + goto error_out; + } + + pageaddr = kmap_atomic(page, KM_USER0); + copied = squashfs_copy_data(pageaddr + bytes, entry, offset, + length - bytes); + if (copied == length - bytes) + memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length); + else + block = entry->next_index; + kunmap_atomic(pageaddr, KM_USER0); + squashfs_cache_put(entry); + } + + flush_dcache_page(page); + SetPageUptodate(page); + unlock_page(page); + return 0; + +error_out: + SetPageError(page); + unlock_page(page); + return 0; +} + + +const struct address_space_operations squashfs_symlink_aops = { + .readpage = squashfs_symlink_readpage +}; |