symlink.c

/*
 *  linux/fs/nfs/symlink.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  Optimization changes Copyright (C) 1994 Florian La Roche
 *
 *  Jun 7 1999, cache symlink lookups in the page cache.  -DaveM
 *
 *  nfs symlink handling code
 */

#define NFS_NEED_XDR_TYPES
#include <linux/time.h>
#include <linux/errno.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs.h>
#include <linux/nfs2.h>
#include <linux/nfs_fs.h>
#include <linux/pagemap.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/smp_lock.h>
#include <linux/namei.h>

/* Symlink caching in the page cache is even more simplistic
 * and straight-forward than readdir caching.
 */

static int nfs_symlink_filler(struct inode *inode, struct page *page)
{
	int error;

	lock_kernel();
	error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
	unlock_kernel();
	if (error < 0)
		goto error;
	SetPageUptodate(page);
	unlock_page(page);
	return 0;

error:
	SetPageError(page);
	unlock_page(page);
	return -EIO;
}

static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct inode *inode = dentry->d_inode;
	struct page *page;
	void *err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
	if (err)
		goto read_failed;
	page = read_cache_page(&inode->i_data, 0,
				(filler_t *)nfs_symlink_filler, inode);
	if (IS_ERR(page)) {
		err = page;
		goto read_failed;
	}
	if (!PageUptodate(page)) {
		err = ERR_PTR(-EIO);
		goto getlink_read_error;
	}
	nd_set_link(nd, kmap(page));
	return page;

getlink_read_error:
	page_cache_release(page);
read_failed:
	nd_set_link(nd, err);
	return NULL;
}

static void nfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
	if (cookie) {
		struct page *page = cookie;
		kunmap(page);
		page_cache_release(page);
	}
}

/*
 * symlinks can't do much...
 */
struct inode_operations nfs_symlink_inode_operations = {
	.readlink	= generic_readlink,
	.follow_link	= nfs_follow_link,
	.put_link	= nfs_put_link,
	.getattr	= nfs_getattr,
	.setattr	= nfs_setattr,
};