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/slab.h>
  23 #include <linux/string.h>
  24 #include <linux/namei.h>
  25
  26 /* Symlink caching in the page cache is even more simplistic
  27  * and straight-forward than readdir caching.
  28  */
  29
  30 static int nfs_symlink_filler(struct inode *inode, struct page *page)
  31 {
  32         int error;
  33
  34         error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
  35         if (error < 0)
  36                 goto error;
  37         SetPageUptodate(page);
  38         unlock_page(page);
  39         return 0;
  40
  41 error:
  42         SetPageError(page);
  43         unlock_page(page);
  44         return -EIO;
  45 }
  46
  47 static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  48 {
  49         struct inode *inode = dentry->d_inode;
  50         struct page *page;
  51         void *err;
  52
  53         err = ERR_PTR(nfs_revalidate_mapping_nolock(inode, inode->i_mapping));
  54         if (err)
  55                 goto read_failed;
  56         page = read_cache_page(&inode->i_data, 0,
  57                                 (filler_t *)nfs_symlink_filler, inode);
  58         if (IS_ERR(page)) {
  59                 err = page;
  60                 goto read_failed;
  61         }
  62         nd_set_link(nd, kmap(page));
  63         return page;
  64
  65 read_failed:
  66         nd_set_link(nd, err);
  67         return NULL;
  68 }
  69
  70 /*
  71  * symlinks can't do much...
  72  */
  73 const struct inode_operations nfs_symlink_inode_operations = {
  74         .readlink       = generic_readlink,
  75         .follow_link    = nfs_follow_link,
  76         .put_link       = page_put_link,
  77         .getattr        = nfs_getattr,
  78         .setattr        = nfs_setattr,
  79 };