root.c

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    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 struct dentry *devpts_root_lookup(struct inode *,struct dentry *);
   21 static int devpts_revalidate(struct dentry *, int);
   22 
   23 struct file_operations devpts_root_operations = {
   24         read:           generic_read_dir,
   25         readdir:        devpts_root_readdir,
   26 };
   27 
   28 struct inode_operations devpts_root_inode_operations = {
   29         lookup:         devpts_root_lookup,
   30 };
   31 
   32 static struct dentry_operations devpts_dentry_operations = {
   33         d_revalidate:   devpts_revalidate,
   34 };
   35 
   36 /*
   37  * The normal naming convention is simply /dev/pts/<number>; this conforms
   38  * to the System V naming convention
   39  */
   40 
   41 #define genptsname(buf,num) sprintf(buf, "%d", num)
   42 
   43 static int devpts_root_readdir(struct file *filp, void *dirent, filldir_t filldir)
   44 {
   45         struct inode * inode = filp->f_dentry->d_inode;
   46         struct devpts_sb_info * sbi = SBI(filp->f_dentry->d_inode->i_sb);
   47         off_t nr;
   48         char numbuf[16];
   49 
   50         nr = filp->f_pos;
   51 
   52         switch(nr)
   53         {
   54         case 0:
   55                 if (filldir(dirent, ".", 1, nr, inode->i_ino, DT_DIR) < 0)
   56                         return 0;
   57                 filp->f_pos = ++nr;
   58                 /* fall through */
   59         case 1:
   60                 if (filldir(dirent, "..", 2, nr, inode->i_ino, DT_DIR) < 0)
   61                         return 0;
   62                 filp->f_pos = ++nr;
   63                 /* fall through */
   64         default:
   65                 while ( nr - 2 < sbi->max_ptys ) {
   66                         int ptynr = nr - 2;
   67                         if ( sbi->inodes[ptynr] ) {
   68                                 genptsname(numbuf, ptynr);
   69                                 if ( filldir(dirent, numbuf, strlen(numbuf), nr, nr, DT_CHR) < 0 )
   70                                         return 0;
   71                         }
   72                         filp->f_pos = ++nr;
   73                 }
   74                 break;
   75         }
   76 
   77         return 0;
   78 }
   79 
   80 /*
   81  * Revalidate is called on every cache lookup.  We use it to check that
   82  * the pty really does still exist.  Never revalidate negative dentries;
   83  * for simplicity (fix later?)
   84  */
   85 static int devpts_revalidate(struct dentry * dentry, int flags)
   86 {
   87         struct devpts_sb_info *sbi;
   88 
   89         if ( !dentry->d_inode )
   90                 return 0;
   91 
   92         sbi = SBI(dentry->d_inode->i_sb);
   93 
   94         return ( sbi->inodes[dentry->d_inode->i_ino - 2] == dentry->d_inode );
   95 }
   96 
   97 static struct dentry *devpts_root_lookup(struct inode * dir, struct dentry * dentry)
   98 {
   99         struct devpts_sb_info *sbi = SBI(dir->i_sb);
  100         unsigned int entry;
  101         int i;
  102         const char *p;
  103 
  104         dentry->d_op    = &devpts_dentry_operations;
  105 
  106         if ( dentry->d_name.len == 1 && dentry->d_name.name[0] == '' ) {
  107                 entry = 0;
  108         } else if ( dentry->d_name.len < 1 ) {
  109                 return NULL;
  110         } else {
  111                 p = dentry->d_name.name;
  112                 if ( *p < '1' || *p > '9' )
  113                         return NULL;
  114                 entry = *p++ - '';
  115 
  116                 for ( i = dentry->d_name.len-1 ; i ; i-- ) {
  117                         unsigned int nentry = *p++ - '';
  118                         if ( nentry > 9 )
  119                                 return NULL;
  120                         if ( entry >= ~0U/10 )
  121                                 return NULL;
  122                         entry = nentry + entry * 10;
  123                 }
  124         }
  125 
  126         if ( entry >= sbi->max_ptys )
  127                 return NULL;
  128 
  129         if ( sbi->inodes[entry] )
  130                 atomic_inc(&sbi->inodes[entry]->i_count);
  131         
  132         d_add(dentry, sbi->inodes[entry]);
  133 
  134         return NULL;
  135 }

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FreeBSD/Linux Kernel Cross Reference sys/fs/devpts/root.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/devpts/root.c