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 dentry *dentry, struct page *page)
  31 {
  32         struct inode *inode = dentry->d_inode;
  33         void *buffer = (void *)kmap(page);
  34         int error;
  35
  36         /* We place the length at the beginning of the page,
  37          * in host byte order, followed by the string.  The
  38          * XDR response verification will NULL terminate it.
  39          */
  40         lock_kernel();
  41         error = NFS_PROTO(inode)->readlink(dentry, buffer,
  42                                            PAGE_CACHE_SIZE - sizeof(u32)-4);
  43         unlock_kernel();
  44         if (error < 0)
  45                 goto error;
  46         SetPageUptodate(page);
  47         kunmap(page);
  48         UnlockPage(page);
  49         return 0;
  50
  51 error:
  52         SetPageError(page);
  53         kunmap(page);
  54         UnlockPage(page);
  55         return -EIO;
  56 }
  57
  58 static char *nfs_getlink(struct dentry *dentry, struct page **ppage)
  59 {
  60         struct inode *inode = dentry->d_inode;
  61         struct page *page;
  62         u32 *p;
  63
  64         /* Caller revalidated the directory inode already. */
  65         page = read_cache_page(&inode->i_data, 0,
  66                                 (filler_t *)nfs_symlink_filler, dentry);
  67         if (IS_ERR(page))
  68                 goto read_failed;
  69         if (!Page_Uptodate(page))
  70                 goto getlink_read_error;
  71         *ppage = page;
  72         p = (u32 *) kmap(page);
  73         return (char*)(p+1);
  74
  75 getlink_read_error:
  76         page_cache_release(page);
  77         return ERR_PTR(-EIO);
  78 read_failed:
  79         return (char*)page;
  80 }
  81
  82 static int nfs_readlink(struct dentry *dentry, char *buffer, int buflen)
  83 {
  84         struct page *page = NULL;
  85         int res = vfs_readlink(dentry,buffer,buflen,nfs_getlink(dentry,&page));
  86         if (page) {
  87                 kunmap(page);
  88                 page_cache_release(page);
  89         }
  90         return res;
  91 }
  92
  93 static int nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
  94 {
  95         struct page *page = NULL;
  96         int res = vfs_follow_link(nd, nfs_getlink(dentry,&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 };