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, void **cookie)
  47 {
  48         struct page *page;
  49         void *err;
  50
  51         if (!dentry) {
  52                 err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
  53                 if (err)
  54                         return err;
  55                 page = find_get_page(inode->i_mapping, 0);
  56                 if (!page)
  57                         return ERR_PTR(-ECHILD);
  58                 if (!PageUptodate(page)) {
  59                         put_page(page);
  60                         return ERR_PTR(-ECHILD);
  61                 }
  62         } else {
  63                 err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
  64                 if (err)
  65                         return err;
  66                 page = read_cache_page(&inode->i_data, 0,
  67                                         (filler_t *)nfs_symlink_filler, inode);
  68                 if (IS_ERR(page))
  69                         return ERR_CAST(page);
  70         }
  71         *cookie = page;
  72         return page_address(page);
  73 }
  74
  75 /*
  76  * symlinks can't do much...
  77  */
  78 const struct inode_operations nfs_symlink_inode_operations = {
  79         .readlink       = generic_readlink,
  80         .get_link       = nfs_get_link,
  81         .put_link       = page_put_link,
  82         .getattr        = nfs_getattr,
  83         .setattr        = nfs_setattr,
  84 };