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  *   do_copyfd:     copies a file descriptor from or to another endpoint
  10  */
  11
  12 #include <sys/select.h>
  13 #include <minix/callnr.h>
  14 #include <minix/u64.h>
  15 #include <assert.h>
  16 #include <sys/stat.h>
  17 #include "fs.h"
  18 #include "file.h"
  19 #include "vnode.h"
  20
  21
  22 #if LOCK_DEBUG
  23 /*===========================================================================*
  24  *                              check_filp_locks                             *
  25  *===========================================================================*/
  26 void check_filp_locks_by_me(void)
  27 {
  28 /* Check whether this thread still has filp locks held */
  29   struct filp *f;
  30   int r;
  31
  32   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
  33         r = mutex_trylock(&f->filp_lock);
  34         if (r == -EDEADLK)
  35                 panic("Thread %d still holds filp lock on filp %p call_nr=%d\n",
  36                       mthread_self(), f, job_call_nr);
  37         else if (r == 0) {
  38                 /* We just obtained the lock, release it */
  39                 mutex_unlock(&f->filp_lock);
  40         }
  41   }
  42 }
  43 #endif
  44
  45 /*===========================================================================*
  46  *                              check_filp_locks                             *
  47  *===========================================================================*/
  48 void check_filp_locks(void)
  49 {
  50   struct filp *f;
  51   int r, count = 0;
  52
  53   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
  54         r = mutex_trylock(&f->filp_lock);
  55         if (r == -EBUSY) {
  56                 /* Mutex is still locked */
  57                 count++;
  58         } else if (r == 0) {
  59                 /* We just obtained a lock, don't want it */
  60                 mutex_unlock(&f->filp_lock);
  61         } else
  62                 panic("filp_lock weird state");
  63   }
  64   if (count) panic("locked filps");
  65 #if 0
  66   else printf("check_filp_locks OK\n");
  67 #endif
  68 }
  69
  70 /*===========================================================================*
  71  *                              init_filps                                   *
  72  *===========================================================================*/
  73 void init_filps(void)
  74 {
  75 /* Initialize filps */
  76   struct filp *f;
  77
  78   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
  79         if (mutex_init(&f->filp_lock, NULL) != 0)
  80                 panic("Failed to initialize filp mutex");
  81   }
  82
  83 }
  84
  85 /*===========================================================================*
  86  *                              get_fd                                       *
  87  *===========================================================================*/
  88 int get_fd(struct fproc *rfp, int start, mode_t bits, int *k, struct filp **fpt)
  89 {
  90 /* Look for a free file descriptor and a free filp slot.  Fill in the mode word
  91  * in the latter, but don't claim either one yet, since the open() or creat()
  92  * may yet fail.
  93  */
  94
  95   register struct filp *f;
  96   register int i;
  97
  98   /* Search the fproc fp_filp table for a free file descriptor. */
  99   for (i = start; i < OPEN_MAX; i++) {
 100         if (rfp->fp_filp[i] == NULL) {
 101                 /* A file descriptor has been located. */
 102                 *k = i;
 103                 break;
 104         }
 105   }
 106
 107   /* Check to see if a file descriptor has been found. */
 108   if (i >= OPEN_MAX) return(EMFILE);
 109
 110   /* If we don't care about a filp, return now */
 111   if (fpt == NULL) return(OK);
 112
 113   /* Now that a file descriptor has been found, look for a free filp slot. */
 114   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 115         assert(f->filp_count >= 0);
 116         if (f->filp_count == 0 && mutex_trylock(&f->filp_lock) == 0) {
 117                 f->filp_mode = bits;
 118                 f->filp_pos = 0;
 119                 f->filp_selectors = 0;
 120                 f->filp_select_ops = 0;
 121                 f->filp_pipe_select_ops = 0;
 122                 f->filp_flags = 0;
 123                 f->filp_select_flags = 0;
 124                 f->filp_softlock = NULL;
 125                 f->filp_ioctl_fp = NULL;
 126                 *fpt = f;
 127                 return(OK);
 128         }
 129   }
 130
 131   /* If control passes here, the filp table must be full.  Report that back. */
 132   return(ENFILE);
 133 }
 134
 135
 136 /*===========================================================================*
 137  *                              get_filp                                     *
 138  *===========================================================================*/
 139 struct filp *get_filp(fild, locktype)
 140 int fild;                       /* file descriptor */
 141 tll_access_t locktype;
 142 {
 143 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
 144
 145   return get_filp2(fp, fild, locktype);
 146 }
 147
 148
 149 /*===========================================================================*
 150  *                              get_filp2                                    *
 151  *===========================================================================*/
 152 struct filp *get_filp2(rfp, fild, locktype)
 153 register struct fproc *rfp;
 154 int fild;                       /* file descriptor */
 155 tll_access_t locktype;
 156 {
 157 /* See if 'fild' refers to a valid file descr.  If so, return its filp ptr. */
 158   struct filp *filp;
 159
 160   filp = NULL;
 161   if (fild < 0 || fild >= OPEN_MAX)
 162         err_code = EBADF;
 163   else if (locktype != VNODE_OPCL && rfp->fp_filp[fild] != NULL &&
 164                 rfp->fp_filp[fild]->filp_mode == FILP_CLOSED)
 165         err_code = EIO; /* disallow all use except close(2) */
 166   else if ((filp = rfp->fp_filp[fild]) == NULL)
 167         err_code = EBADF;
 168   else if (locktype != VNODE_NONE)      /* Only lock the filp if requested */
 169         lock_filp(filp, locktype);      /* All is fine */
 170
 171   return(filp); /* may also be NULL */
 172 }
 173
 174
 175 /*===========================================================================*
 176  *                              find_filp                                    *
 177  *===========================================================================*/
 178 struct filp *find_filp(struct vnode *vp, mode_t bits)
 179 {
 180 /* Find a filp slot that refers to the vnode 'vp' in a way as described
 181  * by the mode bit 'bits'. Used for determining whether somebody is still
 182  * interested in either end of a pipe.  Also used when opening a FIFO to
 183  * find partners to share a filp field with (to shared the file position).
 184  * Like 'get_fd' it performs its job by linear search through the filp table.
 185  */
 186
 187   struct filp *f;
 188
 189   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 190         if (f->filp_count != 0 && f->filp_vno == vp && (f->filp_mode & bits)) {
 191                 return(f);
 192         }
 193   }
 194
 195   /* If control passes here, the filp wasn't there.  Report that back. */
 196   return(NULL);
 197 }
 198
 199 /*===========================================================================*
 200  *                              invalidate_filp                              *
 201  *===========================================================================*/
 202 void invalidate_filp(struct filp *rfilp)
 203 {
 204 /* Invalidate filp. */
 205
 206   rfilp->filp_mode = FILP_CLOSED;
 207 }
 208
 209 /*===========================================================================*
 210  *                      invalidate_filp_by_char_major                        *
 211  *===========================================================================*/
 212 void invalidate_filp_by_char_major(int major)
 213 {
 214   struct filp *f;
 215
 216   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 217         if (f->filp_count != 0 && f->filp_vno != NULL) {
 218                 if (major(f->filp_vno->v_sdev) == major &&
 219                     S_ISCHR(f->filp_vno->v_mode)) {
 220                         invalidate_filp(f);
 221                 }
 222         }
 223   }
 224 }
 225
 226 /*===========================================================================*
 227  *                      invalidate_filp_by_endpt                             *
 228  *===========================================================================*/
 229 void invalidate_filp_by_endpt(endpoint_t proc_e)
 230 {
 231   struct filp *f;
 232
 233   for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
 234         if (f->filp_count != 0 && f->filp_vno != NULL) {
 235                 if (f->filp_vno->v_fs_e == proc_e)
 236                         invalidate_filp(f);
 237         }
 238   }
 239 }
 240
 241 /*===========================================================================*
 242  *                              lock_filp                                    *
 243  *===========================================================================*/
 244 void lock_filp(filp, locktype)
 245 struct filp *filp;
 246 tll_access_t locktype;
 247 {
 248   struct worker_thread *org_self;
 249   struct vnode *vp;
 250
 251   assert(filp->filp_count > 0);
 252   vp = filp->filp_vno;
 253   assert(vp != NULL);
 254
 255   /* Lock vnode only if we haven't already locked it. If already locked by us,
 256    * we're allowed to have one additional 'soft' lock. */
 257   if (tll_locked_by_me(&vp->v_lock)) {
 258         assert(filp->filp_softlock == NULL);
 259         filp->filp_softlock = fp;
 260   } else {
 261         /* We have to make an exception for vnodes belonging to pipes. Even
 262          * read(2) operations on pipes change the vnode and therefore require
 263          * exclusive access.
 264          */
 265         if (S_ISFIFO(vp->v_mode) && locktype == VNODE_READ)
 266                 locktype = VNODE_WRITE;
 267         lock_vnode(vp, locktype);
 268   }
 269
 270   assert(vp->v_ref_count > 0);  /* vnode still in use? */
 271   assert(filp->filp_vno == vp); /* vnode still what we think it is? */
 272
 273   /* First try to get filp lock right off the bat */
 274   if (mutex_trylock(&filp->filp_lock) != 0) {
 275
 276         /* Already in use, let's wait for our turn */
 277         org_self = worker_suspend();
 278
 279         if (mutex_lock(&filp->filp_lock) != 0)
 280                 panic("unable to obtain lock on filp");
 281
 282         worker_resume(org_self);
 283   }
 284 }
 285
 286 /*===========================================================================*
 287  *                              unlock_filp                                  *
 288  *===========================================================================*/
 289 void unlock_filp(filp)
 290 struct filp *filp;
 291 {
 292   /* If this filp holds a soft lock on the vnode, we must be the owner */
 293   if (filp->filp_softlock != NULL)
 294         assert(filp->filp_softlock == fp);
 295
 296   if (filp->filp_count > 0) {
 297         /* Only unlock vnode if filp is still in use */
 298
 299         /* and if we don't hold a soft lock */
 300         if (filp->filp_softlock == NULL) {
 301                 assert(tll_islocked(&(filp->filp_vno->v_lock)));
 302                 unlock_vnode(filp->filp_vno);
 303         }
 304   }
 305
 306   filp->filp_softlock = NULL;
 307   if (mutex_unlock(&filp->filp_lock) != 0)
 308         panic("unable to release lock on filp");
 309 }
 310
 311 /*===========================================================================*
 312  *                              unlock_filps                                 *
 313  *===========================================================================*/
 314 void unlock_filps(filp1, filp2)
 315 struct filp *filp1;
 316 struct filp *filp2;
 317 {
 318 /* Unlock two filps that are tied to the same vnode. As a thread can lock a
 319  * vnode only once, unlocking the vnode twice would result in an error. */
 320
 321   /* No NULL pointers and not equal */
 322   assert(filp1);
 323   assert(filp2);
 324   assert(filp1 != filp2);
 325
 326   /* Must be tied to the same vnode and not NULL */
 327   assert(filp1->filp_vno == filp2->filp_vno);
 328   assert(filp1->filp_vno != NULL);
 329
 330   if (filp1->filp_count > 0 && filp2->filp_count > 0) {
 331         /* Only unlock vnode if filps are still in use */
 332         unlock_vnode(filp1->filp_vno);
 333   }
 334
 335   filp1->filp_softlock = NULL;
 336   filp2->filp_softlock = NULL;
 337   if (mutex_unlock(&filp2->filp_lock) != 0)
 338         panic("unable to release filp lock on filp2");
 339   if (mutex_unlock(&filp1->filp_lock) != 0)
 340         panic("unable to release filp lock on filp1");
 341 }
 342
 343 /*===========================================================================*
 344  *                              close_filp                                   *
 345  *===========================================================================*/
 346 void close_filp(f)
 347 struct filp *f;
 348 {
 349 /* Close a file. Will also unlock filp when done */
 350
 351   int rw;
 352   dev_t dev;
 353   struct vnode *vp;
 354
 355   /* Must be locked */
 356   assert(mutex_trylock(&f->filp_lock) == -EDEADLK);
 357   assert(tll_islocked(&f->filp_vno->v_lock));
 358
 359   vp = f->filp_vno;
 360
 361   if (f->filp_count - 1 == 0 && f->filp_mode != FILP_CLOSED) {
 362         /* Check to see if the file is special. */
 363         if (S_ISCHR(vp->v_mode) || S_ISBLK(vp->v_mode)) {
 364                 dev = vp->v_sdev;
 365                 if (S_ISBLK(vp->v_mode))  {
 366                         lock_bsf();
 367                         if (vp->v_bfs_e == ROOT_FS_E) {
 368                                 /* Invalidate the cache unless the special is
 369                                  * mounted. Assume that the root filesystem's
 370                                  * is open only for fsck.
 371                                  */
 372                                 req_flush(vp->v_bfs_e, dev);
 373                         }
 374                         unlock_bsf();
 375
 376                         (void) bdev_close(dev); /* Ignore errors */
 377                 } else {
 378                         (void) cdev_close(dev); /* Ignore errors */
 379                 }
 380
 381                 f->filp_mode = FILP_CLOSED;
 382         }
 383   }
 384
 385   /* If the inode being closed is a pipe, release everyone hanging on it. */
 386   if (S_ISFIFO(vp->v_mode)) {
 387         rw = (f->filp_mode & R_BIT ? VFS_WRITE : VFS_READ);
 388         release(vp, rw, susp_count);
 389   }
 390
 391   if (--f->filp_count == 0) {
 392         if (S_ISFIFO(vp->v_mode)) {
 393                 /* Last reader or writer is going. Tell PFS about latest
 394                  * pipe size.
 395                  */
 396                 truncate_vnode(vp, vp->v_size);
 397         }
 398
 399         unlock_vnode(f->filp_vno);
 400         put_vnode(f->filp_vno);
 401         f->filp_vno = NULL;
 402         f->filp_mode = FILP_CLOSED;
 403         f->filp_count = 0;
 404   } else if (f->filp_count < 0) {
 405         panic("VFS: invalid filp count: %d ino %llx/%llu", f->filp_count,
 406               vp->v_dev, vp->v_inode_nr);
 407   } else {
 408         unlock_vnode(f->filp_vno);
 409   }
 410
 411   mutex_unlock(&f->filp_lock);
 412 }
 413
 414 /*===========================================================================*
 415  *                              do_copyfd                                    *
 416  *===========================================================================*/
 417 int do_copyfd(void)
 418 {
 419 /* Copy a file descriptor between processes, or close a remote file descriptor.
 420  * This call is used as back-call by device drivers (UDS, VND), and is expected
 421  * to be used in response to an IOCTL to such device drivers.
 422  */
 423   struct fproc *rfp;
 424   struct filp *rfilp;
 425   endpoint_t endpt;
 426   int r, fd, what, slot;
 427
 428   /* This should be replaced with an ACL check. */
 429   if (!super_user) return(EPERM);
 430
 431   endpt = (endpoint_t) job_m_in.VFS_COPYFD_ENDPT;
 432   fd = job_m_in.VFS_COPYFD_FD;
 433   what = job_m_in.VFS_COPYFD_WHAT;
 434
 435   if (isokendpt(endpt, &slot) != OK) return(EINVAL);
 436   rfp = &fproc[slot];
 437
 438   /* FIXME: we should now check that the user process is indeed blocked on an
 439    * IOCTL call, so that we can safely mess with its file descriptors.  We
 440    * currently do not have the necessary state to verify this, so we assume
 441    * that the call is always used in the right way.
 442    */
 443
 444   /* Depending on the operation, get the file descriptor from the caller or the
 445    * user process.  Do not lock the filp yet: we first need to make sure that
 446    * locking it will not result in a deadlock.
 447    */
 448   rfilp = get_filp2((what == COPYFD_TO) ? fp : rfp, fd, VNODE_NONE);
 449   if (rfilp == NULL)
 450         return(err_code);
 451
 452   /* If the filp is involved in an IOCTL by the user process, locking the filp
 453    * here would result in a deadlock.  This would happen if a user process
 454    * passes in the file descriptor to the device node on which it is performing
 455    * the IOCTL.  We do not allow manipulation of such device nodes.  In
 456    * practice, this only applies to block-special files (and thus VND), because
 457    * character-special files (as used by UDS) are unlocked during the IOCTL.
 458    */
 459   if (rfilp->filp_ioctl_fp == rfp)
 460         return(EBADF);
 461
 462   /* Now we can safely lock the filp, copy or close it, and unlock it again. */
 463   lock_filp(rfilp, VNODE_READ);
 464
 465   switch (what) {
 466   case COPYFD_FROM:
 467         rfp = fp;
 468
 469         /* FALLTHROUGH */
 470   case COPYFD_TO:
 471         /* Find a free file descriptor slot in the local or remote process. */
 472         for (fd = 0; fd < OPEN_MAX; fd++)
 473                 if (rfp->fp_filp[fd] == NULL)
 474                         break;
 475
 476         /* If found, fill the slot and return the slot number. */
 477         if (fd < OPEN_MAX) {
 478                 rfp->fp_filp[fd] = rfilp;
 479                 rfilp->filp_count++;
 480                 r = fd;
 481         } else
 482                 r = EMFILE;
 483
 484         break;
 485
 486   case COPYFD_CLOSE:
 487         /* This should be used ONLY to revert a successful copy-to operation,
 488          * and assumes that the filp is still in use by the caller as well.
 489          */
 490         if (rfilp->filp_count > 1) {
 491                 rfilp->filp_count--;
 492                 rfp->fp_filp[fd] = NULL;
 493                 r = OK;
 494         } else
 495                 r = EBADF;
 496
 497         break;
 498
 499   default:
 500         r = EINVAL;
 501   }
 502
 503   unlock_filp(rfilp);
 504
 505   return(r);
 506 }