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 #define NFS_NEED_XDR_TYPES
  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/slab.h>
  24 #include <linux/string.h>
  25 #include <linux/smp_lock.h>
  26 #include <linux/namei.h>
  27
  28 /* Symlink caching in the page cache is even more simplistic
  29  * and straight-forward than readdir caching.
  30  */
  31
  32 static int nfs_symlink_filler(struct inode *inode, struct page *page)
  33 {
  34         int error;
  35
  36         lock_kernel();
  37         error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
  38         unlock_kernel();
  39         if (error < 0)
  40                 goto error;
  41         SetPageUptodate(page);
  42         unlock_page(page);
  43         return 0;
  44
  45 error:
  46         SetPageError(page);
  47         unlock_page(page);
  48         return -EIO;
  49 }
  50
  51 static void *nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  52 {
  53         struct inode *inode = dentry->d_inode;
  54         struct page *page;
  55         void *err = ERR_PTR(nfs_revalidate_inode(NFS_SERVER(inode), inode));
  56         if (err)
  57                 goto read_failed;
  58         page = read_cache_page(&inode->i_data, 0,
  59                                 (filler_t *)nfs_symlink_filler, inode);
  60         if (IS_ERR(page)) {
  61                 err = page;
  62                 goto read_failed;
  63         }
  64         if (!PageUptodate(page)) {
  65                 err = ERR_PTR(-EIO);
  66                 goto getlink_read_error;
  67         }
  68         nd_set_link(nd, kmap(page));
  69         return page;
  70
  71 getlink_read_error:
  72         page_cache_release(page);
  73 read_failed:
  74         nd_set_link(nd, err);
  75         return NULL;
  76 }
  77
  78 static void nfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
  79 {
  80         if (cookie) {
  81                 struct page *page = cookie;
  82                 kunmap(page);
  83                 page_cache_release(page);
  84         }
  85 }
  86
  87 /*
  88  * symlinks can't do much...
  89  */
  90 struct inode_operations nfs_symlink_inode_operations = {
  91         .readlink       = generic_readlink,
  92         .follow_link    = nfs_follow_link,
  93         .put_link       = nfs_put_link,
  94         .getattr        = nfs_getattr,
  95         .setattr        = nfs_setattr,
  96 };