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(struct file *file, struct folio *folio)
  30 {
  31         struct inode *inode = folio->mapping->host;
  32         int error;
  33
  34         error = NFS_PROTO(inode)->readlink(inode, &folio->page, 0, PAGE_SIZE);
  35         folio_end_read(folio, error == 0);
  36         return error;
  37 }
  38
  39 static const char *nfs_get_link(struct dentry *dentry,
  40                                 struct inode *inode,
  41                                 struct delayed_call *done)
  42 {
  43         struct page *page;
  44         void *err;
  45
  46         if (!dentry) {
  47                 err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
  48                 if (err)
  49                         return err;
  50                 page = find_get_page(inode->i_mapping, 0);
  51                 if (!page)
  52                         return ERR_PTR(-ECHILD);
  53                 if (!PageUptodate(page)) {
  54                         put_page(page);
  55                         return ERR_PTR(-ECHILD);
  56                 }
  57         } else {
  58                 err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
  59                 if (err)
  60                         return err;
  61                 page = read_cache_page(&inode->i_data, 0, nfs_symlink_filler,
  62                                 NULL);
  63                 if (IS_ERR(page))
  64                         return ERR_CAST(page);
  65         }
  66         set_delayed_call(done, page_put_link, page);
  67         return page_address(page);
  68 }
  69
  70 /*
  71  * symlinks can't do much...
  72  */
  73 const struct inode_operations nfs_symlink_inode_operations = {
  74         .get_link       = nfs_get_link,
  75         .getattr        = nfs_getattr,
  76         .setattr        = nfs_setattr,
  77 };