fs/devpts/root.c

   1 /* -*- linux-c -*- --------------------------------------------------------- *
   2  *
   3  * linux/fs/devpts/root.c
   4  *
   5  *  Copyright 1998 H. Peter Anvin -- All Rights Reserved
   6  *
   7  * This file is part of the Linux kernel and is made available under
   8  * the terms of the GNU General Public License, version 2, or at your
   9  * option, any later version, incorporated herein by reference.
  10  *
  11  * ------------------------------------------------------------------------- */
  12
  13 #include <linux/errno.h>
  14 #include <linux/stat.h>
  15 #include <linux/param.h>
  16 #include <linux/string.h>
  17 #include "devpts_i.h"
  18
  19 static int devpts_root_readdir(struct file *,void *,filldir_t);
  20 static int devpts_root_lookup(struct inode *,struct dentry *);
  21 static int devpts_revalidate(struct dentry *);
  22
  23 static struct file_operations devpts_root_operations = {
  24         NULL,                   /* llseek */
  25         NULL,                   /* read */
  26         NULL,                   /* write */
  27         devpts_root_readdir,    /* readdir */
  28         NULL,                   /* poll */
  29         NULL,                   /* ioctl */
  30         NULL,                   /* mmap */
  31         NULL,                   /* open */
  32         NULL,                   /* flush */
  33         NULL,                   /* release */
  34         NULL,                   /* fsync */
  35         NULL,                   /* fasync */
  36         NULL,                   /* check_media_change */
  37         NULL,                   /* revalidate */
  38         NULL                    /* lock */
  39 };
  40
  41 struct inode_operations devpts_root_inode_operations = {
  42         &devpts_root_operations, /* file operations */
  43         NULL,                   /* create */
  44         devpts_root_lookup,     /* lookup */
  45         NULL,                   /* link */
  46         NULL,                   /* unlink */
  47         NULL,                   /* symlink */
  48         NULL,                   /* mkdir */
  49         NULL,                   /* rmdir */
  50         NULL,                   /* mknod */
  51         NULL,                   /* rename */
  52         NULL,                   /* readlink */
  53         NULL,                   /* follow_link */
  54         NULL,                   /* readpage */
  55         NULL,                   /* writepage */
  56         NULL,                   /* bmap */
  57         NULL,                   /* truncate */
  58         NULL,                   /* permission */
  59         NULL,                   /* smap */
  60         NULL,                   /* updatepage */
  61         NULL                    /* revalidate */
  62 };
  63
  64 static struct dentry_operations devpts_dentry_operations = {
  65         devpts_revalidate,      /* d_revalidate */
  66         NULL,                   /* d_hash */
  67         NULL,                   /* d_compare */
  68 };
  69
  70 /*
  71  * The normal naming convention is simply /dev/pts/<number>; this conforms
  72  * to the System V naming convention
  73  */
  74
  75 #define genptsname(buf,num) sprintf(buf, "%d", num)
  76
  77 static int devpts_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
  78 {
  79         struct inode * inode = filp->f_dentry->d_inode;
  80         struct devpts_sb_info * sbi = SBI(filp->f_dentry->d_inode->i_sb);
  81         off_t nr;
  82         char numbuf[16];
  83
  84         if (!inode || !S_ISDIR(inode->i_mode))
  85                 return -ENOTDIR;
  86
  87         nr = filp->f_pos;
  88
  89         switch(nr)
  90         {
  91         case 0:
  92                 if (filldir(dirent, ".", 1, nr, inode->i_ino) < 0)
  93                         return 0;
  94                 filp->f_pos = ++nr;
  95                 /* fall through */
  96         case 1:
  97                 if (filldir(dirent, "..", 2, nr, inode->i_ino) < 0)
  98                         return 0;
  99                 filp->f_pos = ++nr;
 100                 /* fall through */
 101         default:
 102                 while ( nr < sbi->max_ptys ) {
 103                         int ptynr = nr - 2;
 104                         if ( sbi->inodes[ptynr] ) {
 105                                 genptsname(numbuf, ptynr);
 106                                 if ( filldir(dirent, numbuf, strlen(numbuf), nr, nr) < 0 )
 107                                         return 0;
 108                         }
 109                         filp->f_pos = ++nr;
 110                 }
 111                 break;
 112         }
 113
 114         return 0;
 115 }
 116
 117 /*
 118  * Revalidate is called on every cache lookup.  We use it to check that
 119  * the pty really does still exist.  Never revalidate negative dentries;
 120  * for simplicity (fix later?)
 121  */
 122 static int devpts_revalidate(struct dentry * dentry)
 123 {
 124         struct devpts_sb_info *sbi;
 125
 126         if ( !dentry->d_inode )
 127                 return 0;
 128
 129         sbi = SBI(dentry->d_inode->i_sb);
 130
 131         return ( sbi->inodes[dentry->d_inode->i_ino - 2] == dentry->d_inode );
 132 }
 133
 134 static int devpts_root_lookup(struct inode * dir, struct dentry * dentry)
 135 {
 136         struct devpts_sb_info *sbi = SBI(dir->i_sb);
 137         int entry, i;
 138         const char *p;
 139
 140         if (!S_ISDIR(dir->i_mode))
 141                 return -ENOTDIR;
 142
 143         dentry->d_inode = NULL; /* Assume failure */
 144         dentry->d_op    = &devpts_dentry_operations;
 145
 146         if ( dentry->d_name.len == 1 && dentry->d_name.name[0] == '0' ) {
 147                 entry = 0;
 148         } else if ( dentry->d_name.len < 1 ) {
 149                 return 0;
 150         } else {
 151                 p = dentry->d_name.name;
 152                 if ( *p < '1' || *p > '9' )
 153                         return 0;
 154                 entry = *p++ - '0';
 155
 156                 for ( i = dentry->d_name.len-1 ; i ; i-- ) {
 157                         if ( *p < '0' || *p > '9' )
 158                                 return 0;
 159                         entry *= 10;
 160                         entry += (*p++ - '0');
 161                 }
 162         }
 163
 164         dentry->d_inode = sbi->inodes[entry];
 165         if ( dentry->d_inode )
 166                 dentry->d_inode->i_count++;
 167
 168         d_add(dentry, dentry->d_inode);
 169
 170         return 0;
 171 }