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
  24 /* Symlink caching in the page cache is even more simplistic
  25  * and straight-forward than readdir caching.
  26  */
  27
  28 static int nfs_symlink_filler(struct inode *inode, struct page *page)
  29 {
  30         int error;
  31
  32         error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
  33         if (error < 0)
  34                 goto error;
  35         SetPageUptodate(page);
  36         unlock_page(page);
  37         return 0;
  38
  39 error:
  40         SetPageError(page);
  41         unlock_page(page);
  42         return -EIO;
  43 }
  44
  45 static const char *nfs_get_link(struct dentry *dentry,
  46                                 struct inode *inode,
  47                                 struct delayed_call *done)
  48 {
  49         struct page *page;
  50         void *err;
  51
  52         if (!dentry) {
  53                 err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
  54                 if (err)
  55                         return err;
  56                 page = find_get_page(inode->i_mapping, 0);
  57                 if (!page)
  58                         return ERR_PTR(-ECHILD);
  59                 if (!PageUptodate(page)) {
  60                         put_page(page);
  61                         return ERR_PTR(-ECHILD);
  62                 }
  63         } else {
  64                 err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
  65                 if (err)
  66                         return err;
  67                 page = read_cache_page(&inode->i_data, 0,
  68                                         (filler_t *)nfs_symlink_filler, inode);
  69                 if (IS_ERR(page))
  70                         return ERR_CAST(page);
  71         }
  72         set_delayed_call(done, page_put_link, page);
  73         return page_address(page);
  74 }
  75
  76 /*
  77  * symlinks can't do much...
  78  */
  79 const struct inode_operations nfs_symlink_inode_operations = {
  80         .get_link       = nfs_get_link,
  81         .getattr        = nfs_getattr,
  82         .setattr        = nfs_setattr,
  83 };