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/*

 *  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/sched.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>

/* 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;

        /* We place the length at the beginning of the page,

         * in host byte order, followed by the string.  The

         * XDR response verification will NULL terminate it.

         */

        lock_kernel();

        error = NFS_PROTO(inode)->readlink(inode, page);

        unlock_kernel();

        if (error < 0)

                goto error;

        SetPageUptodate(page);

        UnlockPage(page);

        return 0;

error:

        SetPageError(page);

        UnlockPage(page);

        return -EIO;

}

static char *nfs_getlink(struct inode *inode, struct page **ppage)

{

        struct page *page;

        u32 *p;

        /* Caller revalidated the directory inode already. */

        page = read_cache_page(&inode->i_data, 0,

                                (filler_t *)nfs_symlink_filler, inode);

        if (IS_ERR(page))

                goto read_failed;

        if (!Page_Uptodate(page))

                goto getlink_read_error;

        *ppage = page;

        p = kmap(page);

        return (char*)(p+1);

getlink_read_error:

        page_cache_release(page);

        return ERR_PTR(-EIO);

read_failed:

        return (char*)page;

}

static int nfs_readlink(struct dentry *dentry, char *buffer, int buflen)

{

        struct inode *inode = dentry->d_inode;

        struct page *page = NULL;

        int res = vfs_readlink(dentry,buffer,buflen,nfs_getlink(inode,&page));

        if (page) {

                kunmap(page);

                page_cache_release(page);

        }

        return res;

}

static int nfs_follow_link(struct dentry *dentry, struct nameidata *nd)

{

        struct inode *inode = dentry->d_inode;

        struct page *page = NULL;

        int res = vfs_follow_link(nd, nfs_getlink(inode,&page));

        if (page) {

                kunmap(page);

                page_cache_release(page);

        }

        return res;

}

/*

 * symlinks can't do much...

 */

struct inode_operations nfs_symlink_inode_operations = {

        readlink:       nfs_readlink,

        follow_link:    nfs_follow_link,

        revalidate:     nfs_revalidate,

        setattr:        nfs_notify_change,

};