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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_fs.h>
#include <linux/nfs.h>
#include <linux/pagemap.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/malloc.h>
#include <linux/string.h>
#include <asm/uaccess.h>
static int nfs_readlink(struct dentry *, char *, int);
static struct dentry *nfs_follow_link(struct dentry *, struct dentry *, unsigned int);
/*
* symlinks can't do much...
*/
struct inode_operations nfs_symlink_inode_operations = {
NULL, /* no file-operations */
NULL, /* create */
NULL, /* lookup */
NULL, /* link */
NULL, /* unlink */
NULL, /* symlink */
NULL, /* mkdir */
NULL, /* rmdir */
NULL, /* mknod */
NULL, /* rename */
nfs_readlink, /* readlink */
nfs_follow_link, /* follow_link */
NULL, /* get_block */
NULL, /* readpage */
NULL, /* writepage */
NULL, /* flushpage */
NULL, /* truncate */
NULL, /* permission */
NULL, /* smap */
NULL /* revalidate */
};
/* Symlink caching in the page cache is even more simplistic
* and straight-forward than readdir caching.
*/
static struct page *try_to_get_symlink_page(struct dentry *dentry, struct inode *inode)
{
struct nfs_readlinkargs rl_args;
struct page *page, **hash, *page_cache;
page = NULL;
page_cache = page_cache_alloc();
if (!page_cache)
goto out;
hash = page_hash(&inode->i_data, 0);
repeat:
page = __find_lock_page(&inode->i_data, 0, hash);
if (page) {
page_cache_free(page_cache);
goto unlock_out;
}
page = page_cache;
if (add_to_page_cache_unique(page, &inode->i_data, 0, hash)) {
page_cache_release(page);
goto repeat;
}
/* 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.
*/
rl_args.fh = NFS_FH(dentry);
rl_args.buffer = (const void *)page_address(page_cache);
if (rpc_call(NFS_CLIENT(inode), NFSPROC_READLINK,
&rl_args, NULL, 0) < 0)
goto error;
SetPageUptodate(page);
unlock_out:
UnlockPage(page);
out:
return page;
error:
SetPageError(page);
goto unlock_out;
}
static int nfs_readlink(struct dentry *dentry, char *buffer, int buflen)
{
struct inode *inode = dentry->d_inode;
struct page *page;
u32 *p, len;
/* Caller revalidated the directory inode already. */
page = find_get_page(&inode->i_data, 0);
if (!page)
goto no_readlink_page;
if (!Page_Uptodate(page))
goto readlink_read_error;
success:
p = (u32 *) page_address(page);
len = *p++;
if (len > buflen)
len = buflen;
copy_to_user(buffer, p, len);
page_cache_release(page);
return len;
no_readlink_page:
page = try_to_get_symlink_page(dentry, inode);
if (!page)
goto no_page;
if (Page_Uptodate(page))
goto success;
readlink_read_error:
page_cache_release(page);
no_page:
return -EIO;
}
static struct dentry *
nfs_follow_link(struct dentry *dentry, struct dentry *base, unsigned int follow)
{
struct dentry *result;
struct inode *inode = dentry->d_inode;
struct page *page;
u32 *p;
/* Caller revalidated the directory inode already. */
page = find_get_page(&inode->i_data, 0);
if (!page)
goto no_followlink_page;
if (!Page_Uptodate(page))
goto followlink_read_error;
success:
p = (u32 *) page_address(page);
result = lookup_dentry((char *) (p + 1), base, follow);
page_cache_release(page);
return result;
no_followlink_page:
page = try_to_get_symlink_page(dentry, inode);
if (!page)
goto no_page;
if (Page_Uptodate(page))
goto success;
followlink_read_error:
page_cache_release(page);
no_page:
return ERR_PTR(-EIO);
}
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