release/src-rt-6.x.4708/linux/linux-2.6.36/fs/nfs/symlink.c

   1 /*
   2  *  linux/fs/nfs/symlink.c
   3  *
   4  *  Copyright (C) 1992  Rick Sladkey
   5  *
   6  *  Optimization changes Copyright (C) 1994 Florian La Roche
   7  *
   8  *  Jun 7 1999, cache symlink lookups in the page cache.  -DaveM
   9  *
  10  *  nfs symlink handling code
  11  */
  12
  13 #include <linux/time.h>
  14 #include <linux/errno.h>
  15 #include <linux/sunrpc/clnt.h>
  16 #include <linux/nfs.h>
  17 #include <linux/nfs2.h>
  18 #include <linux/nfs_fs.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/stat.h>
  21 #include <linux/mm.h>
  22 #include <linux/string.h>
  23 #include <linux/namei.h>
  24
  25 /* Symlink caching in the page cache is even more simplistic
  26  * and straight-forward than readdir caching.
  27  */
  28
  29 static int nfs_symlink_filler(struct inode *inode, struct page *page)
  30 {
  31         int error;
  32
  33         error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
  34         if (error < 0)
  35                 goto error;
  36         SetPageUptodate(page);
  37         unlock_page(page);
  38         return 0;
  39
  40 error:
  41         SetPageError(page);
  42         unlock_page(page);
  43         return -EIO;
  44 }
  45
  46 static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  47 {
  48         struct inode *inode = dentry->d_inode;
  49         struct page *page;
  50         void *err;
  51
  52         err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
  53         if (err)
  54                 goto read_failed;
  55         page = read_cache_page(&inode->i_data, 0,
  56                                 (filler_t *)nfs_symlink_filler, inode);
  57         if (IS_ERR(page)) {
  58                 err = page;
  59                 goto read_failed;
  60         }
  61         nd_set_link(nd, kmap(page));
  62         return page;
  63
  64 read_failed:
  65         nd_set_link(nd, err);
  66         return NULL;
  67 }
  68
  69 /*
  70  * symlinks can't do much...
  71  */
  72 const struct inode_operations nfs_symlink_inode_operations = {
  73         .readlink       = generic_readlink,
  74         .follow_link    = nfs_follow_link,
  75         .put_link       = page_put_link,
  76         .getattr        = nfs_getattr,
  77         .setattr        = nfs_setattr,
  78 };