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 vnode
   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 #include <minix/u64.h>
  13 #include <assert.h>
  14
  15 #include "fs.h"
  16 #include "file.h"
  17 #include "fproc.h"
  18
  19 #include "vnode.h"
  20
  21 /*===========================================================================*
  22  *                              get_fd                                       *
  23  *===========================================================================*/
  24 PUBLIC int get_fd(int start, mode_t bits, int *k, struct filp **fpt)
  25 {
  26 /* Look for a free file descriptor and a free filp slot.  Fill in the mode word
  27  * in the latter, but don't claim either one yet, since the open() or creat()
  28  * may yet fail.
  29  */
  30
  31   register struct filp *f;
  32   register int i;
  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 (i >= OPEN_MAX) return(EMFILE);
  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         assert(f->filp_count >= 0);
  49         if (f->filp_count == 0) {
  50                 f->filp_mode = bits;
  51                 f->filp_pos = cvu64(0);
  52                 f->filp_selectors = 0;
  53                 f->filp_select_ops = 0;
  54                 f->filp_pipe_select_ops = 0;
  55                 f->filp_flags = 0;
  56                 *fpt = f;
  57                 return(OK);
  58         }
  59   }
  60
  61   /* If control passes here, the filp table must be full.  Report that back. */
  62   return(ENFILE);
  63 }
  64
  65 /*===========================================================================*
  66  *                              get_filp                                     *
  67  *===========================================================================*/
  68 PUBLIC struct filp *get_filp(fild)
  69 int fild;                       /* file descriptor */
  70 {
  71 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  72
  73   return get_filp2(fp, fild);
  74 }
  75
  76 /*===========================================================================*
  77  *                              get_filp2                                    *
  78  *===========================================================================*/
  79 PUBLIC struct filp *get_filp2(rfp, fild)
  80 register struct fproc *rfp;
  81 int fild;                       /* file descriptor */
  82 {
  83 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
  84
  85   err_code = EBADF;
  86   if (fild < 0 || fild >= OPEN_MAX ) return(NIL_FILP);
  87   return(rfp->fp_filp[fild]);   /* may also be NIL_FILP */
  88 }
  89
  90 /*===========================================================================*
  91  *                              find_filp                                    *
  92  *===========================================================================*/
  93 PUBLIC struct filp *find_filp(register struct vnode *vp, mode_t bits)
  94 {
  95 /* Find a filp slot that refers to the vnode 'vp' in a way as described
  96  * by the mode bit 'bits'. Used for determining whether somebody is still
  97  * interested in either end of a pipe.  Also used when opening a FIFO to
  98  * find partners to share a filp field with (to shared the file position).
  99  * Like 'get_fd' it performs its job by linear search through the filp table.
 100  */
 101
 102   register struct filp *f;
 103
 104   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 105         if (f->filp_count != 0 && f->filp_vno == vp && (f->filp_mode & bits)){
 106                 assert(f->filp_count > 0);
 107                 return(f);
 108         }
 109   }
 110
 111   /* If control passes here, the filp wasn't there.  Report that back. */
 112   return(NIL_FILP);
 113 }
 114
 115 /*===========================================================================*
 116  *                              inval_filp                                   *
 117  *===========================================================================*/
 118 PUBLIC int inval_filp(struct filp *fp)
 119 {
 120     int f, fd, n = 0;
 121     for(f = 0; f < NR_PROCS; f++) {
 122         if(fproc[f].fp_pid == PID_FREE) continue;
 123         for(fd = 0; fd < OPEN_MAX; fd++) {
 124             if(fproc[f].fp_filp[fd] && fproc[f].fp_filp[fd] == fp) {
 125                 fproc[f].fp_filp[fd] = NIL_FILP;
 126                 n++;
 127             }
 128         }
 129     }
 130
 131     return n;
 132 }