lustre/obdfs/symlink.c

   1 /*
   2  *  linux/fs/ext2/symlink.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  from
  10  *
  11  *  linux/fs/minix/symlink.c
  12  *
  13  *  Copyright (C) 1991, 1992  Linus Torvalds
  14  *
  15  *  ext2 symlink handling code
  16  *
  17  * Modified for OBDFS:
  18  *  Copyright (C) 1999 Seagate Technology Inc. (author: braam@stelias.com)
  19  */
  20
  21 #include <asm/uaccess.h>
  22
  23 #include <linux/errno.h>
  24 #include <linux/fs.h>
  25 #include <linux/sched.h>
  26 #include <linux/mm.h>
  27 #include <linux/stat.h>
  28 #include <linux/locks.h>
  29
  30 #include <linux/obd_support.h> /* for ENTRY and EXIT only */
  31 #include <linux/obdfs.h>
  32
  33 static int obdfs_readlink (struct dentry *, char *, int);
  34 static struct dentry *obdfs_follow_link(struct dentry *, struct dentry *, unsigned int);
  35
  36 /*
  37  * symlinks can't do much...
  38  */
  39 struct inode_operations obdfs_symlink_inode_operations = {
  40         NULL,                   /* no file-operations */
  41         NULL,                   /* create */
  42         NULL,                   /* lookup */
  43         NULL,                   /* link */
  44         NULL,                   /* unlink */
  45         NULL,                   /* symlink */
  46         NULL,                   /* mkdir */
  47         NULL,                   /* rmdir */
  48         NULL,                   /* mknod */
  49         NULL,                   /* rename */
  50         obdfs_readlink,         /* readlink */
  51         obdfs_follow_link,      /* follow_link */
  52         NULL,                   /* get_block */
  53         NULL,                   /* readpage */
  54         NULL,                   /* writepage */
  55         NULL,                   /* truncate */
  56         NULL,                   /* permission */
  57         NULL                    /* revalidate */
  58 };
  59
  60 static struct dentry * obdfs_follow_link(struct dentry * dentry,
  61                                          struct dentry *base,
  62                                          unsigned int follow)
  63 {
  64         struct inode *inode = dentry->d_inode;
  65         struct page *page = NULL;
  66         char * link;
  67
  68         ENTRY;
  69         link = (char *) inode->u.ext2_i.i_data;
  70         if (inode->i_blocks) {
  71                 IDEBUG(inode);
  72                 page = obdfs_getpage(inode, 0, 0, 0);
  73                 PDEBUG(page, "follow_link");
  74                 if (!page) {
  75                         dput(base);
  76                         EXIT;
  77                         return ERR_PTR(-EIO);
  78                 }
  79                 link = (char *)page_address(page);
  80         }
  81         UPDATE_ATIME(inode);
  82         base = lookup_dentry(link, base, follow);
  83         if (page) {
  84                 page_cache_release(page);
  85         }
  86         EXIT;
  87         return base;
  88 }
  89
  90 static int obdfs_readlink (struct dentry * dentry, char * buffer, int buflen)
  91 {
  92         struct inode *inode = dentry->d_inode;
  93         struct page *page = NULL;
  94         char * link;
  95         int i;
  96
  97         ENTRY;
  98         if (buflen > inode->i_sb->s_blocksize - 1)
  99                 buflen = inode->i_sb->s_blocksize - 1;
 100
 101         link = (char *) inode->u.ext2_i.i_data;
 102         if (inode->i_blocks) {
 103                 IDEBUG(inode);
 104                 page = obdfs_getpage(inode, 0, 0, 0);
 105                 PDEBUG(page, "readlink");
 106                 if (!page) {
 107                         EXIT;
 108                         return 0;
 109                 }
 110                 link = (char *)page_address(page);
 111         }
 112
 113         i = 0;
 114         while (i < buflen && link[i])
 115                 i++;
 116         if (copy_to_user(buffer, link, i))
 117                 i = -EFAULT;
 118         if (page) {
 119                 page_cache_release(page);
 120         }
 121         EXIT;
 122         return i;
 123 } /* obdfs_readlink */