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/sched.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/malloc.h>
  24 #include <linux/string.h>
  25 #include <linux/smp_lock.h>
  26
  27 /* Symlink caching in the page cache is even more simplistic
  28  * and straight-forward than readdir caching.
  29  */
  30 static int nfs_symlink_filler(struct inode *inode, struct page *page)
  31 {
  32         void *buffer = kmap(page);
  33         int error;
  34
  35         /* We place the length at the beginning of the page,
  36          * in host byte order, followed by the string.  The
  37          * XDR response verification will NULL terminate it.
  38          */
  39         lock_kernel();
  40         error = NFS_PROTO(inode)->readlink(inode, buffer,
  41                                            PAGE_CACHE_SIZE - sizeof(u32)-4);
  42         unlock_kernel();
  43         if (error < 0)
  44                 goto error;
  45         SetPageUptodate(page);
  46         kunmap(page);
  47         UnlockPage(page);
  48         return 0;
  49
  50 error:
  51         SetPageError(page);
  52         kunmap(page);
  53         UnlockPage(page);
  54         return -EIO;
  55 }
  56
  57 static char *nfs_getlink(struct inode *inode, struct page **ppage)
  58 {
  59         struct page *page;
  60         u32 *p;
  61
  62         /* Caller revalidated the directory inode already. */
  63         page = read_cache_page(&inode->i_data, 0,
  64                                 (filler_t *)nfs_symlink_filler, inode);
  65         if (IS_ERR(page))
  66                 goto read_failed;
  67         if (!Page_Uptodate(page))
  68                 goto getlink_read_error;
  69         *ppage = page;
  70         p = kmap(page);
  71         return (char*)(p+1);
  72
  73 getlink_read_error:
  74         page_cache_release(page);
  75         return ERR_PTR(-EIO);
  76 read_failed:
  77         return (char*)page;
  78 }
  79
  80 static int nfs_readlink(struct dentry *dentry, char *buffer, int buflen)
  81 {
  82         struct inode *inode = dentry->d_inode;
  83         struct page *page = NULL;
  84         int res = vfs_readlink(dentry,buffer,buflen,nfs_getlink(inode,&page));
  85         if (page) {
  86                 kunmap(page);
  87                 page_cache_release(page);
  88         }
  89         return res;
  90 }
  91
  92 static int nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  93 {
  94         struct inode *inode = dentry->d_inode;
  95         struct page *page = NULL;
  96         int res = vfs_follow_link(nd, nfs_getlink(inode,&page));
  97         if (page) {
  98                 kunmap(page);
  99                 page_cache_release(page);
 100         }
 101         return res;
 102 }
 103
 104 /*
 105  * symlinks can't do much...
 106  */
 107 struct inode_operations nfs_symlink_inode_operations = {
 108         readlink:       nfs_readlink,
 109         follow_link:    nfs_follow_link,
 110         revalidate:     nfs_revalidate,
 111         setattr:        nfs_notify_change,
 112 };