fs/nfs/symlink.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/nfs/symlink.c
   4  *
   5  *  Copyright (C) 1992  Rick Sladkey
   6  *
   7  *  Optimization changes Copyright (C) 1994 Florian La Roche
   8  *
   9  *  Jun 7 1999, cache symlink lookups in the page cache.  -DaveM
  10  *
  11  *  nfs symlink handling code
  12  */
  13
  14 #include <linux/time.h>
  15 #include <linux/errno.h>
  16 #include <linux/sunrpc/clnt.h>
  17 #include <linux/nfs.h>
  18 #include <linux/nfs2.h>
  19 #include <linux/nfs_fs.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/stat.h>
  22 #include <linux/mm.h>
  23 #include <linux/string.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(void *data, struct page *page)
  30 {
  31         struct inode *inode = data;
  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 const char *nfs_get_link(struct dentry *dentry,
  48                                 struct inode *inode,
  49                                 struct delayed_call *done)
  50 {
  51         struct page *page;
  52         void *err;
  53
  54         if (!dentry) {
  55                 err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
  56                 if (err)
  57                         return err;
  58                 page = find_get_page(inode->i_mapping, 0);
  59                 if (!page)
  60                         return ERR_PTR(-ECHILD);
  61                 if (!PageUptodate(page)) {
  62                         put_page(page);
  63                         return ERR_PTR(-ECHILD);
  64                 }
  65         } else {
  66                 err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
  67                 if (err)
  68                         return err;
  69                 page = read_cache_page(&inode->i_data, 0, nfs_symlink_filler,
  70                                 inode);
  71                 if (IS_ERR(page))
  72                         return ERR_CAST(page);
  73         }
  74         set_delayed_call(done, page_put_link, page);
  75         return page_address(page);
  76 }
  77
  78 /*
  79  * symlinks can't do much...
  80  */
  81 const struct inode_operations nfs_symlink_inode_operations = {
  82         .get_link       = nfs_get_link,
  83         .getattr        = nfs_getattr,
  84         .setattr        = nfs_setattr,
  85 };