servers/vfs/filedes.c

   1 /* This file contains the procedures that manipulate file descriptors.
   2  *
   3  * The entry points into this file are
   4  *   get_fd:     look for free file descriptor and free filp slots
   5  *   get_filp:   look up the filp entry for a given file descriptor
   6  *   find_filp:  find a filp slot that points to a given inode
   7  *   inval_filp: invalidate a filp and associated fd's, only let close()
   8  *               happen on it
   9  */
  10
  11 #include <sys/select.h>
  12
  13 #include "fs.h"
  14 #include "file.h"
  15 #include "fproc.h"
  16
  17 #include "vnode.h"
  18
  19 /*===========================================================================*
  20  *                              get_fd                                       *
  21  *===========================================================================*/
  22 PUBLIC int get_fd(int start, mode_t bits, int *k, struct filp **fpt)
  23 {
  24 /* Look for a free file descriptor and a free filp slot.  Fill in the mode word
  25  * in the latter, but don't claim either one yet, since the open() or creat()
  26  * may yet fail.
  27  */
  28
  29   register struct filp *f;
  30   register int i;
  31
  32   *k = -1;                      /* we need a way to tell if file desc found */
  33
  34   /* Search the fproc fp_filp table for a free file descriptor. */
  35   for (i = start; i < OPEN_MAX; i++) {
  36         if (fp->fp_filp[i] == NIL_FILP && !FD_ISSET(i, &fp->fp_filp_inuse)) {
  37                 /* A file descriptor has been located. */
  38                 *k = i;
  39                 break;
  40         }
  41   }
  42
  43   /* Check to see if a file descriptor has been found. */
  44   if (*k < 0) return(EMFILE);   /* this is why we initialized k to -1 */
  45
  46   /* Now that a file descriptor has been found, look for a free filp slot. */
  47   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
  48         if (f->filp_count == 0) {
  49                 f->filp_mode = bits;
  50                 f->filp_pos = 0L;
  51                 f->filp_selectors = 0;
  52                 f->filp_select_ops = 0;
  53                 f->filp_pipe_select_ops = 0;
  54                 f->filp_flags = 0;
  55                 *fpt = f;
  56                 return(OK);
  57         }
  58   }
  59
  60   /* If control passes here, the filp table must be full.  Report that back. */
  61   return(ENFILE);
  62 }
  63
  64 /*===========================================================================*
  65  *                              get_filp                                     *
  66  *===========================================================================*/
  67 PUBLIC struct filp *get_filp(fild)
  68 int fild;                       /* file descriptor */
  69 {
  70 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  71
  72   return get_filp2(fp, fild);
  73 }
  74
  75 /*===========================================================================*
  76  *                              get_filp2                                    *
  77  *===========================================================================*/
  78 PUBLIC struct filp *get_filp2(rfp, fild)
  79 register struct fproc *rfp;
  80 int fild;                       /* file descriptor */
  81 {
  82 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  83
  84   err_code = EBADF;
  85   if (fild < 0 || fild >= OPEN_MAX ) return(NIL_FILP);
  86   return(rfp->fp_filp[fild]);   /* may also be NIL_FILP */
  87 }
  88
  89 /*===========================================================================*
  90  *                              find_filp                                    *
  91  *===========================================================================*/
  92 PUBLIC struct filp *find_filp(register struct vnode *vp, mode_t bits)
  93 {
  94 /* Find a filp slot that refers to the inode 'rip' in a way as described
  95  * by the mode bit 'bits'. Used for determining whether somebody is still
  96  * interested in either end of a pipe.  Also used when opening a FIFO to
  97  * find partners to share a filp field with (to shared the file position).
  98  * Like 'get_fd' it performs its job by linear search through the filp table.
  99  */
 100
 101   register struct filp *f;
 102
 103   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 104         if (f->filp_count != 0 && f->filp_vno == vp && (f->filp_mode & bits)){
 105                 return(f);
 106         }
 107   }
 108
 109   /* If control passes here, the filp wasn't there.  Report that back. */
 110   return(NIL_FILP);
 111 }
 112
 113 /*===========================================================================*
 114  *                              inval_filp                                   *
 115  *===========================================================================*/
 116 PUBLIC int inval_filp(struct filp *fp)
 117 {
 118     int f, fd, n = 0;
 119     for(f = 0; f < NR_PROCS; f++) {
 120         if(fproc[f].fp_pid == PID_FREE) continue;
 121         for(fd = 0; fd < OPEN_MAX; fd++) {
 122             if(fproc[f].fp_filp[fd] && fproc[f].fp_filp[fd] == fp) {
 123                 fproc[f].fp_filp[fd] = NIL_FILP;
 124                 n++;
 125             }
 126         }
 127     }
 128
 129     return n;
 130 }