symlink.c

linux 内核源代码

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 *  linux/cluster/ssi/cfs/symlink.c
 *
 *	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 of
 *	the License, 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, GOOD TITLE
 *	or NON INFRINGEMENT.  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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *	Questions/Comments/Bugfixes to [e-mail]
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  Optimization changes Copyright (C) 1994 Florian La Roche
 *
 *  Jun 7 1999, cache symlink lookups in the page cache.  -DaveM
 *
 *  Portions Copyright (C) 2001 Compaq Computer Corporation
 *
 *  ocfs2 symlink handling code.
 *
 *  Copyright (C) 2004, 2005 Oracle.
 *
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/utsname.h>

#define MLOG_MASK_PREFIX ML_NAMEI
#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "file.h"
#include "inode.h"
#include "journal.h"
#include "symlink.h"

#include "buffer_head_io.h"

static char *ocfs2_page_getlink(struct dentry * dentry,
				struct page **ppage);
static char *ocfs2_fast_symlink_getlink(struct inode *inode,
					struct buffer_head **bh);

/* get the link contents into pagecache */
static char *ocfs2_page_getlink(struct dentry * dentry,
				struct page **ppage)
{
	struct page * page;
	struct address_space *mapping = dentry->d_inode->i_mapping;
	page = read_mapping_page(mapping, 0, NULL);
	if (IS_ERR(page))
		goto sync_fail;
	*ppage = page;
	return kmap(page);

sync_fail:
	return (char*)page;
}

static char *ocfs2_fast_symlink_getlink(struct inode *inode,
					struct buffer_head **bh)
{
	int status;
	char *link = NULL;
	struct ocfs2_dinode *fe;

	mlog_entry_void();

	status = ocfs2_read_block(OCFS2_SB(inode->i_sb),
				  OCFS2_I(inode)->ip_blkno,
				  bh,
				  OCFS2_BH_CACHED,
				  inode);
	if (status < 0) {
		mlog_errno(status);
		link = ERR_PTR(status);
		goto bail;
	}

	fe = (struct ocfs2_dinode *) (*bh)->b_data;
	link = (char *) fe->id2.i_symlink;
bail:
	mlog_exit(status);

	return link;
}

static int ocfs2_readlink(struct dentry *dentry,
			  char __user *buffer,
			  int buflen)
{
	int ret;
	char *link;
	struct buffer_head *bh = NULL;
	struct inode *inode = dentry->d_inode;

	mlog_entry_void();

	link = ocfs2_fast_symlink_getlink(inode, &bh);
	if (IS_ERR(link)) {
		ret = PTR_ERR(link);
		goto out;
	}

	/*
	 * Without vfsmount we can't update atime now,
	 * but we will update atime here ultimately.
	 */
	ret = vfs_readlink(dentry, buffer, buflen, link);

	brelse(bh);
out:
	mlog_exit(ret);
	return ret;
}

static void *ocfs2_follow_link(struct dentry *dentry,
			       struct nameidata *nd)
{
	int status;
	char *link;
	struct inode *inode = dentry->d_inode;
	struct page *page = NULL;
	struct buffer_head *bh = NULL;
	
	if (ocfs2_inode_is_fast_symlink(inode))
		link = ocfs2_fast_symlink_getlink(inode, &bh);
	else
		link = ocfs2_page_getlink(dentry, &page);
	if (IS_ERR(link)) {
		status = PTR_ERR(link);
		mlog_errno(status);
		goto bail;
	}

	status = vfs_follow_link(nd, link);

bail:
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
	if (bh)
		brelse(bh);

	return ERR_PTR(status);
}

const struct inode_operations ocfs2_symlink_inode_operations = {
	.readlink	= page_readlink,
	.follow_link	= ocfs2_follow_link,
	.getattr	= ocfs2_getattr,
};
const struct inode_operations ocfs2_fast_symlink_inode_operations = {
	.readlink	= ocfs2_readlink,
	.follow_link	= ocfs2_follow_link,
	.getattr	= ocfs2_getattr,
};