fs/fuse/dev.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>
   4
   5   This program can be distributed under the terms of the GNU GPL.
   6   See the file COPYING.
   7 */
   8
   9 #include "fuse_i.h"
  10
  11 #include <linux/init.h>
  12 #include <linux/module.h>
  13 #include <linux/poll.h>
  14 #include <linux/uio.h>
  15 #include <linux/miscdevice.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/file.h>
  18 #include <linux/slab.h>
  19
  20 MODULE_ALIAS_MISCDEV(FUSE_MINOR);
  21
  22 static struct kmem_cache *fuse_req_cachep;
  23
  24 static struct fuse_conn *fuse_get_conn(struct file *file)
  25 {
  26         /*
  27          * Lockless access is OK, because file->private data is set
  28          * once during mount and is valid until the file is released.
  29          */
  30         return file->private_data;
  31 }
  32
  33 static void fuse_request_init(struct fuse_req *req)
  34 {
  35         memset(req, 0, sizeof(*req));
  36         INIT_LIST_HEAD(&req->list);
  37         INIT_LIST_HEAD(&req->intr_entry);
  38         init_waitqueue_head(&req->waitq);
  39         atomic_set(&req->count, 1);
  40 }
  41
  42 struct fuse_req *fuse_request_alloc(void)
  43 {
  44         struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, GFP_KERNEL);
  45         if (req)
  46                 fuse_request_init(req);
  47         return req;
  48 }
  49
  50 void fuse_request_free(struct fuse_req *req)
  51 {
  52         kmem_cache_free(fuse_req_cachep, req);
  53 }
  54
  55 static void block_sigs(sigset_t *oldset)
  56 {
  57         sigset_t mask;
  58
  59         siginitsetinv(&mask, sigmask(SIGKILL));
  60         sigprocmask(SIG_BLOCK, &mask, oldset);
  61 }
  62
  63 static void restore_sigs(sigset_t *oldset)
  64 {
  65         sigprocmask(SIG_SETMASK, oldset, NULL);
  66 }
  67
  68 static void __fuse_get_request(struct fuse_req *req)
  69 {
  70         atomic_inc(&req->count);
  71 }
  72
  73 /* Must be called with > 1 refcount */
  74 static void __fuse_put_request(struct fuse_req *req)
  75 {
  76         BUG_ON(atomic_read(&req->count) < 2);
  77         atomic_dec(&req->count);
  78 }
  79
  80 static void fuse_req_init_context(struct fuse_req *req)
  81 {
  82         req->in.h.uid = current->fsuid;
  83         req->in.h.gid = current->fsgid;
  84         req->in.h.pid = current->pid;
  85 }
  86
  87 struct fuse_req *fuse_get_req(struct fuse_conn *fc)
  88 {
  89         struct fuse_req *req;
  90         sigset_t oldset;
  91         int intr;
  92         int err;
  93
  94         atomic_inc(&fc->num_waiting);
  95         block_sigs(&oldset);
  96         intr = wait_event_interruptible(fc->blocked_waitq, !fc->blocked);
  97         restore_sigs(&oldset);
  98         err = -EINTR;
  99         if (intr)
 100                 goto out;
 101
 102         err = -ENOTCONN;
 103         if (!fc->connected)
 104                 goto out;
 105
 106         req = fuse_request_alloc();
 107         err = -ENOMEM;
 108         if (!req)
 109                 goto out;
 110
 111         fuse_req_init_context(req);
 112         req->waiting = 1;
 113         return req;
 114
 115  out:
 116         atomic_dec(&fc->num_waiting);
 117         return ERR_PTR(err);
 118 }
 119
 120 /*
 121  * Return request in fuse_file->reserved_req.  However that may
 122  * currently be in use.  If that is the case, wait for it to become
 123  * available.
 124  */
 125 static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
 126                                          struct file *file)
 127 {
 128         struct fuse_req *req = NULL;
 129         struct fuse_file *ff = file->private_data;
 130
 131         do {
 132                 wait_event(fc->blocked_waitq, ff->reserved_req);
 133                 spin_lock(&fc->lock);
 134                 if (ff->reserved_req) {
 135                         req = ff->reserved_req;
 136                         ff->reserved_req = NULL;
 137                         get_file(file);
 138                         req->stolen_file = file;
 139                 }
 140                 spin_unlock(&fc->lock);
 141         } while (!req);
 142
 143         return req;
 144 }
 145
 146 /*
 147  * Put stolen request back into fuse_file->reserved_req
 148  */
 149 static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
 150 {
 151         struct file *file = req->stolen_file;
 152         struct fuse_file *ff = file->private_data;
 153
 154         spin_lock(&fc->lock);
 155         fuse_request_init(req);
 156         BUG_ON(ff->reserved_req);
 157         ff->reserved_req = req;
 158         wake_up(&fc->blocked_waitq);
 159         spin_unlock(&fc->lock);
 160         fput(file);
 161 }
 162
 163 /*
 164  * Gets a requests for a file operation, always succeeds
 165  *
 166  * This is used for sending the FLUSH request, which must get to
 167  * userspace, due to POSIX locks which may need to be unlocked.
 168  *
 169  * If allocation fails due to OOM, use the reserved request in
 170  * fuse_file.
 171  *
 172  * This is very unlikely to deadlock accidentally, since the
 173  * filesystem should not have it's own file open.  If deadlock is
 174  * intentional, it can still be broken by "aborting" the filesystem.
 175  */
 176 struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
 177 {
 178         struct fuse_req *req;
 179
 180         atomic_inc(&fc->num_waiting);
 181         wait_event(fc->blocked_waitq, !fc->blocked);
 182         req = fuse_request_alloc();
 183         if (!req)
 184                 req = get_reserved_req(fc, file);
 185
 186         fuse_req_init_context(req);
 187         req->waiting = 1;
 188         return req;
 189 }
 190
 191 void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
 192 {
 193         if (atomic_dec_and_test(&req->count)) {
 194                 if (req->waiting)
 195                         atomic_dec(&fc->num_waiting);
 196
 197                 if (req->stolen_file)
 198                         put_reserved_req(fc, req);
 199                 else
 200                         fuse_request_free(req);
 201         }
 202 }
 203
 204 /*
 205  * This function is called when a request is finished.  Either a reply
 206  * has arrived or it was aborted (and not yet sent) or some error
 207  * occurred during communication with userspace, or the device file
 208  * was closed.  The requester thread is woken up (if still waiting),
 209  * the 'end' callback is called if given, else the reference to the
 210  * request is released
 211  *
 212  * Called with fc->lock, unlocks it
 213  */
 214 static void request_end(struct fuse_conn *fc, struct fuse_req *req)
 215         __releases(fc->lock)
 216 {
 217         void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
 218         req->end = NULL;
 219         list_del(&req->list);
 220         list_del(&req->intr_entry);
 221         req->state = FUSE_REQ_FINISHED;
 222         if (req->background) {
 223                 if (fc->num_background == FUSE_MAX_BACKGROUND) {
 224                         fc->blocked = 0;
 225                         wake_up_all(&fc->blocked_waitq);
 226                 }
 227                 if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
 228                         clear_bdi_congested(&fc->bdi, READ);
 229                         clear_bdi_congested(&fc->bdi, WRITE);
 230                 }
 231                 fc->num_background--;
 232         }
 233         spin_unlock(&fc->lock);
 234         dput(req->dentry);
 235         mntput(req->vfsmount);
 236         if (req->file)
 237                 fput(req->file);
 238         wake_up(&req->waitq);
 239         if (end)
 240                 end(fc, req);
 241         else
 242                 fuse_put_request(fc, req);
 243 }
 244
 245 static void wait_answer_interruptible(struct fuse_conn *fc,
 246                                       struct fuse_req *req)
 247 {
 248         if (signal_pending(current))
 249                 return;
 250
 251         spin_unlock(&fc->lock);
 252         wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED);
 253         spin_lock(&fc->lock);
 254 }
 255
 256 static void queue_interrupt(struct fuse_conn *fc, struct fuse_req *req)
 257 {
 258         list_add_tail(&req->intr_entry, &fc->interrupts);
 259         wake_up(&fc->waitq);
 260         kill_fasync(&fc->fasync, SIGIO, POLL_IN);
 261 }
 262
 263 /* Called with fc->lock held.  Releases, and then reacquires it. */
 264 static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
 265 {
 266         if (!fc->no_interrupt) {
 267                 /* Any signal may interrupt this */
 268                 wait_answer_interruptible(fc, req);
 269
 270                 if (req->aborted)
 271                         goto aborted;
 272                 if (req->state == FUSE_REQ_FINISHED)
 273                         return;
 274
 275                 req->interrupted = 1;
 276                 if (req->state == FUSE_REQ_SENT)
 277                         queue_interrupt(fc, req);
 278         }
 279
 280         if (req->force) {
 281                 spin_unlock(&fc->lock);
 282                 wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
 283                 spin_lock(&fc->lock);
 284         } else {
 285                 sigset_t oldset;
 286
 287                 /* Only fatal signals may interrupt this */
 288                 block_sigs(&oldset);
 289                 wait_answer_interruptible(fc, req);
 290                 restore_sigs(&oldset);
 291         }
 292
 293         if (req->aborted)
 294                 goto aborted;
 295         if (req->state == FUSE_REQ_FINISHED)
 296                 return;
 297
 298         req->out.h.error = -EINTR;
 299         req->aborted = 1;
 300
 301  aborted:
 302         if (req->locked) {
 303                 /* This is uninterruptible sleep, because data is
 304                    being copied to/from the buffers of req.  During
 305                    locked state, there mustn't be any filesystem
 306                    operation (e.g. page fault), since that could lead
 307                    to deadlock */
 308                 spin_unlock(&fc->lock);
 309                 wait_event(req->waitq, !req->locked);
 310                 spin_lock(&fc->lock);
 311         }
 312         if (req->state == FUSE_REQ_PENDING) {
 313                 list_del(&req->list);
 314                 __fuse_put_request(req);
 315         } else if (req->state == FUSE_REQ_SENT) {
 316                 spin_unlock(&fc->lock);
 317                 wait_event(req->waitq, req->state == FUSE_REQ_FINISHED);
 318                 spin_lock(&fc->lock);
 319         }
 320 }
 321
 322 static unsigned len_args(unsigned numargs, struct fuse_arg *args)
 323 {
 324         unsigned nbytes = 0;
 325         unsigned i;
 326
 327         for (i = 0; i < numargs; i++)
 328                 nbytes += args[i].size;
 329
 330         return nbytes;
 331 }
 332
 333 static u64 fuse_get_unique(struct fuse_conn *fc)
 334  {
 335         fc->reqctr++;
 336         /* zero is special */
 337         if (fc->reqctr == 0)
 338                 fc->reqctr = 1;
 339
 340         return fc->reqctr;
 341 }
 342
 343 static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
 344 {
 345         req->in.h.unique = fuse_get_unique(fc);
 346         req->in.h.len = sizeof(struct fuse_in_header) +
 347                 len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
 348         list_add_tail(&req->list, &fc->pending);
 349         req->state = FUSE_REQ_PENDING;
 350         if (!req->waiting) {
 351                 req->waiting = 1;
 352                 atomic_inc(&fc->num_waiting);
 353         }
 354         wake_up(&fc->waitq);
 355         kill_fasync(&fc->fasync, SIGIO, POLL_IN);
 356 }
 357
 358 void request_send(struct fuse_conn *fc, struct fuse_req *req)
 359 {
 360         req->isreply = 1;
 361         spin_lock(&fc->lock);
 362         if (!fc->connected)
 363                 req->out.h.error = -ENOTCONN;
 364         else if (fc->conn_error)
 365                 req->out.h.error = -ECONNREFUSED;
 366         else {
 367                 queue_request(fc, req);
 368                 /* acquire extra reference, since request is still needed
 369                    after request_end() */
 370                 __fuse_get_request(req);
 371
 372                 request_wait_answer(fc, req);
 373         }
 374         spin_unlock(&fc->lock);
 375 }
 376
 377 static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
 378 {
 379         spin_lock(&fc->lock);
 380         if (fc->connected) {
 381                 req->background = 1;
 382                 fc->num_background++;
 383                 if (fc->num_background == FUSE_MAX_BACKGROUND)
 384                         fc->blocked = 1;
 385                 if (fc->num_background == FUSE_CONGESTION_THRESHOLD) {
 386                         set_bdi_congested(&fc->bdi, READ);
 387                         set_bdi_congested(&fc->bdi, WRITE);
 388                 }
 389
 390                 queue_request(fc, req);
 391                 spin_unlock(&fc->lock);
 392         } else {
 393                 req->out.h.error = -ENOTCONN;
 394                 request_end(fc, req);
 395         }
 396 }
 397
 398 void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req)
 399 {
 400         req->isreply = 0;
 401         request_send_nowait(fc, req);
 402 }
 403
 404 void request_send_background(struct fuse_conn *fc, struct fuse_req *req)
 405 {
 406         req->isreply = 1;
 407         request_send_nowait(fc, req);
 408 }
 409
 410 /*
 411  * Lock the request.  Up to the next unlock_request() there mustn't be
 412  * anything that could cause a page-fault.  If the request was already
 413  * aborted bail out.
 414  */
 415 static int lock_request(struct fuse_conn *fc, struct fuse_req *req)
 416 {
 417         int err = 0;
 418         if (req) {
 419                 spin_lock(&fc->lock);
 420                 if (req->aborted)
 421                         err = -ENOENT;
 422                 else
 423                         req->locked = 1;
 424                 spin_unlock(&fc->lock);
 425         }
 426         return err;
 427 }
 428
 429 /*
 430  * Unlock request.  If it was aborted during being locked, the
 431  * requester thread is currently waiting for it to be unlocked, so
 432  * wake it up.
 433  */
 434 static void unlock_request(struct fuse_conn *fc, struct fuse_req *req)
 435 {
 436         if (req) {
 437                 spin_lock(&fc->lock);
 438                 req->locked = 0;
 439                 if (req->aborted)
 440                         wake_up(&req->waitq);
 441                 spin_unlock(&fc->lock);
 442         }
 443 }
 444
 445 struct fuse_copy_state {
 446         struct fuse_conn *fc;
 447         int write;
 448         struct fuse_req *req;
 449         const struct iovec *iov;
 450         unsigned long nr_segs;
 451         unsigned long seglen;
 452         unsigned long addr;
 453         struct page *pg;
 454         void *mapaddr;
 455         void *buf;
 456         unsigned len;
 457 };
 458
 459 static void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *fc,
 460                            int write, struct fuse_req *req,
 461                            const struct iovec *iov, unsigned long nr_segs)
 462 {
 463         memset(cs, 0, sizeof(*cs));
 464         cs->fc = fc;
 465         cs->write = write;
 466         cs->req = req;
 467         cs->iov = iov;
 468         cs->nr_segs = nr_segs;
 469 }
 470
 471 /* Unmap and put previous page of userspace buffer */
 472 static void fuse_copy_finish(struct fuse_copy_state *cs)
 473 {
 474         if (cs->mapaddr) {
 475                 kunmap_atomic(cs->mapaddr, KM_USER0);
 476                 if (cs->write) {
 477                         flush_dcache_page(cs->pg);
 478                         set_page_dirty_lock(cs->pg);
 479                 }
 480                 put_page(cs->pg);
 481                 cs->mapaddr = NULL;
 482         }
 483 }
 484
 485 /*
 486  * Get another pagefull of userspace buffer, and map it to kernel
 487  * address space, and lock request
 488  */
 489 static int fuse_copy_fill(struct fuse_copy_state *cs)
 490 {
 491         unsigned long offset;
 492         int err;
 493
 494         unlock_request(cs->fc, cs->req);
 495         fuse_copy_finish(cs);
 496         if (!cs->seglen) {
 497                 BUG_ON(!cs->nr_segs);
 498                 cs->seglen = cs->iov[0].iov_len;
 499                 cs->addr = (unsigned long) cs->iov[0].iov_base;
 500                 cs->iov ++;
 501                 cs->nr_segs --;
 502         }
 503         down_read(&current->mm->mmap_sem);
 504         err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0,
 505                              &cs->pg, NULL);
 506         up_read(&current->mm->mmap_sem);
 507         if (err < 0)
 508                 return err;
 509         BUG_ON(err != 1);
 510         offset = cs->addr % PAGE_SIZE;
 511         cs->mapaddr = kmap_atomic(cs->pg, KM_USER0);
 512         cs->buf = cs->mapaddr + offset;
 513         cs->len = min(PAGE_SIZE - offset, cs->seglen);
 514         cs->seglen -= cs->len;
 515         cs->addr += cs->len;
 516
 517         return lock_request(cs->fc, cs->req);
 518 }
 519
 520 /* Do as much copy to/from userspace buffer as we can */
 521 static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
 522 {
 523         unsigned ncpy = min(*size, cs->len);
 524         if (val) {
 525                 if (cs->write)
 526                         memcpy(cs->buf, *val, ncpy);
 527                 else
 528                         memcpy(*val, cs->buf, ncpy);
 529                 *val += ncpy;
 530         }
 531         *size -= ncpy;
 532         cs->len -= ncpy;
 533         cs->buf += ncpy;
 534         return ncpy;
 535 }
 536
 537 /*
 538  * Copy a page in the request to/from the userspace buffer.  Must be
 539  * done atomically
 540  */
 541 static int fuse_copy_page(struct fuse_copy_state *cs, struct page *page,
 542                           unsigned offset, unsigned count, int zeroing)
 543 {
 544         if (page && zeroing && count < PAGE_SIZE) {
 545                 void *mapaddr = kmap_atomic(page, KM_USER1);
 546                 memset(mapaddr, 0, PAGE_SIZE);
 547                 kunmap_atomic(mapaddr, KM_USER1);
 548         }
 549         while (count) {
 550                 int err;
 551                 if (!cs->len && (err = fuse_copy_fill(cs)))
 552                         return err;
 553                 if (page) {
 554                         void *mapaddr = kmap_atomic(page, KM_USER1);
 555                         void *buf = mapaddr + offset;
 556                         offset += fuse_copy_do(cs, &buf, &count);
 557                         kunmap_atomic(mapaddr, KM_USER1);
 558                 } else
 559                         offset += fuse_copy_do(cs, NULL, &count);
 560         }
 561         if (page && !cs->write)
 562                 flush_dcache_page(page);
 563         return 0;
 564 }
 565
 566 /* Copy pages in the request to/from userspace buffer */
 567 static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
 568                            int zeroing)
 569 {
 570         unsigned i;
 571         struct fuse_req *req = cs->req;
 572         unsigned offset = req->page_offset;
 573         unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset);
 574
 575         for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
 576                 struct page *page = req->pages[i];
 577                 int err = fuse_copy_page(cs, page, offset, count, zeroing);
 578                 if (err)
 579                         return err;
 580
 581                 nbytes -= count;
 582                 count = min(nbytes, (unsigned) PAGE_SIZE);
 583                 offset = 0;
 584         }
 585         return 0;
 586 }
 587
 588 /* Copy a single argument in the request to/from userspace buffer */
 589 static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
 590 {
 591         while (size) {
 592                 int err;
 593                 if (!cs->len && (err = fuse_copy_fill(cs)))
 594                         return err;
 595                 fuse_copy_do(cs, &val, &size);
 596         }
 597         return 0;
 598 }
 599
 600 /* Copy request arguments to/from userspace buffer */
 601 static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
 602                           unsigned argpages, struct fuse_arg *args,
 603                           int zeroing)
 604 {
 605         int err = 0;
 606         unsigned i;
 607
 608         for (i = 0; !err && i < numargs; i++)  {
 609                 struct fuse_arg *arg = &args[i];
 610                 if (i == numargs - 1 && argpages)
 611                         err = fuse_copy_pages(cs, arg->size, zeroing);
 612                 else
 613                         err = fuse_copy_one(cs, arg->value, arg->size);
 614         }
 615         return err;
 616 }
 617
 618 static int request_pending(struct fuse_conn *fc)
 619 {
 620         return !list_empty(&fc->pending) || !list_empty(&fc->interrupts);
 621 }
 622
 623 /* Wait until a request is available on the pending list */
 624 static void request_wait(struct fuse_conn *fc)
 625 {
 626         DECLARE_WAITQUEUE(wait, current);
 627
 628         add_wait_queue_exclusive(&fc->waitq, &wait);
 629         while (fc->connected && !request_pending(fc)) {
 630                 set_current_state(TASK_INTERRUPTIBLE);
 631                 if (signal_pending(current))
 632                         break;
 633
 634                 spin_unlock(&fc->lock);
 635                 schedule();
 636                 spin_lock(&fc->lock);
 637         }
 638         set_current_state(TASK_RUNNING);
 639         remove_wait_queue(&fc->waitq, &wait);
 640 }
 641
 642 /*
 643  * Transfer an interrupt request to userspace
 644  *
 645  * Unlike other requests this is assembled on demand, without a need
 646  * to allocate a separate fuse_req structure.
 647  *
 648  * Called with fc->lock held, releases it
 649  */
 650 static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_req *req,
 651                                const struct iovec *iov, unsigned long nr_segs)
 652         __releases(fc->lock)
 653 {
 654         struct fuse_copy_state cs;
 655         struct fuse_in_header ih;
 656         struct fuse_interrupt_in arg;
 657         unsigned reqsize = sizeof(ih) + sizeof(arg);
 658         int err;
 659
 660         list_del_init(&req->intr_entry);
 661         req->intr_unique = fuse_get_unique(fc);
 662         memset(&ih, 0, sizeof(ih));
 663         memset(&arg, 0, sizeof(arg));
 664         ih.len = reqsize;
 665         ih.opcode = FUSE_INTERRUPT;
 666         ih.unique = req->intr_unique;
 667         arg.unique = req->in.h.unique;
 668
 669         spin_unlock(&fc->lock);
 670         if (iov_length(iov, nr_segs) < reqsize)
 671                 return -EINVAL;
 672
 673         fuse_copy_init(&cs, fc, 1, NULL, iov, nr_segs);
 674         err = fuse_copy_one(&cs, &ih, sizeof(ih));
 675         if (!err)
 676                 err = fuse_copy_one(&cs, &arg, sizeof(arg));
 677         fuse_copy_finish(&cs);
 678
 679         return err ? err : reqsize;
 680 }
 681
 682 /*
 683  * Read a single request into the userspace filesystem's buffer.  This
 684  * function waits until a request is available, then removes it from
 685  * the pending list and copies request data to userspace buffer.  If
 686  * no reply is needed (FORGET) or request has been aborted or there
 687  * was an error during the copying then it's finished by calling
 688  * request_end().  Otherwise add it to the processing list, and set
 689  * the 'sent' flag.
 690  */
 691 static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
 692                               unsigned long nr_segs, loff_t pos)
 693 {
 694         int err;
 695         struct fuse_req *req;
 696         struct fuse_in *in;
 697         struct fuse_copy_state cs;
 698         unsigned reqsize;
 699         struct file *file = iocb->ki_filp;
 700         struct fuse_conn *fc = fuse_get_conn(file);
 701         if (!fc)
 702                 return -EPERM;
 703
 704  restart:
 705         spin_lock(&fc->lock);
 706         err = -EAGAIN;
 707         if ((file->f_flags & O_NONBLOCK) && fc->connected &&
 708             !request_pending(fc))
 709                 goto err_unlock;
 710
 711         request_wait(fc);
 712         err = -ENODEV;
 713         if (!fc->connected)
 714                 goto err_unlock;
 715         err = -ERESTARTSYS;
 716         if (!request_pending(fc))
 717                 goto err_unlock;
 718
 719         if (!list_empty(&fc->interrupts)) {
 720                 req = list_entry(fc->interrupts.next, struct fuse_req,
 721                                  intr_entry);
 722                 return fuse_read_interrupt(fc, req, iov, nr_segs);
 723         }
 724
 725         req = list_entry(fc->pending.next, struct fuse_req, list);
 726         req->state = FUSE_REQ_READING;
 727         list_move(&req->list, &fc->io);
 728
 729         in = &req->in;
 730         reqsize = in->h.len;
 731         /* If request is too large, reply with an error and restart the read */
 732         if (iov_length(iov, nr_segs) < reqsize) {
 733                 req->out.h.error = -EIO;
 734                 /* SETXATTR is special, since it may contain too large data */
 735                 if (in->h.opcode == FUSE_SETXATTR)
 736                         req->out.h.error = -E2BIG;
 737                 request_end(fc, req);
 738                 goto restart;
 739         }
 740         spin_unlock(&fc->lock);
 741         fuse_copy_init(&cs, fc, 1, req, iov, nr_segs);
 742         err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
 743         if (!err)
 744                 err = fuse_copy_args(&cs, in->numargs, in->argpages,
 745                                      (struct fuse_arg *) in->args, 0);
 746         fuse_copy_finish(&cs);
 747         spin_lock(&fc->lock);
 748         req->locked = 0;
 749         if (!err && req->aborted)
 750                 err = -ENOENT;
 751         if (err) {
 752                 if (!req->aborted)
 753                         req->out.h.error = -EIO;
 754                 request_end(fc, req);
 755                 return err;
 756         }
 757         if (!req->isreply)
 758                 request_end(fc, req);
 759         else {
 760                 req->state = FUSE_REQ_SENT;
 761                 list_move_tail(&req->list, &fc->processing);
 762                 if (req->interrupted)
 763                         queue_interrupt(fc, req);
 764                 spin_unlock(&fc->lock);
 765         }
 766         return reqsize;
 767
 768  err_unlock:
 769         spin_unlock(&fc->lock);
 770         return err;
 771 }
 772
 773 /* Look up request on processing list by unique ID */
 774 static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique)
 775 {
 776         struct list_head *entry;
 777
 778         list_for_each(entry, &fc->processing) {
 779                 struct fuse_req *req;
 780                 req = list_entry(entry, struct fuse_req, list);
 781                 if (req->in.h.unique == unique || req->intr_unique == unique)
 782                         return req;
 783         }
 784         return NULL;
 785 }
 786
 787 static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
 788                          unsigned nbytes)
 789 {
 790         unsigned reqsize = sizeof(struct fuse_out_header);
 791
 792         if (out->h.error)
 793                 return nbytes != reqsize ? -EINVAL : 0;
 794
 795         reqsize += len_args(out->numargs, out->args);
 796
 797         if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
 798                 return -EINVAL;
 799         else if (reqsize > nbytes) {
 800                 struct fuse_arg *lastarg = &out->args[out->numargs-1];
 801                 unsigned diffsize = reqsize - nbytes;
 802                 if (diffsize > lastarg->size)
 803                         return -EINVAL;
 804                 lastarg->size -= diffsize;
 805         }
 806         return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
 807                               out->page_zeroing);
 808 }
 809
 810 /*
 811  * Write a single reply to a request.  First the header is copied from
 812  * the write buffer.  The request is then searched on the processing
 813  * list by the unique ID found in the header.  If found, then remove
 814  * it from the list and copy the rest of the buffer to the request.
 815  * The request is finished by calling request_end()
 816  */
 817 static ssize_t fuse_dev_write(struct kiocb *iocb, const struct iovec *iov,
 818                                unsigned long nr_segs, loff_t pos)
 819 {
 820         int err;
 821         unsigned nbytes = iov_length(iov, nr_segs);
 822         struct fuse_req *req;
 823         struct fuse_out_header oh;
 824         struct fuse_copy_state cs;
 825         struct fuse_conn *fc = fuse_get_conn(iocb->ki_filp);
 826         if (!fc)
 827                 return -EPERM;
 828
 829         fuse_copy_init(&cs, fc, 0, NULL, iov, nr_segs);
 830         if (nbytes < sizeof(struct fuse_out_header))
 831                 return -EINVAL;
 832
 833         err = fuse_copy_one(&cs, &oh, sizeof(oh));
 834         if (err)
 835                 goto err_finish;
 836         err = -EINVAL;
 837         if (!oh.unique || oh.error <= -1000 || oh.error > 0 ||
 838             oh.len != nbytes)
 839                 goto err_finish;
 840
 841         spin_lock(&fc->lock);
 842         err = -ENOENT;
 843         if (!fc->connected)
 844                 goto err_unlock;
 845
 846         req = request_find(fc, oh.unique);
 847         if (!req)
 848                 goto err_unlock;
 849
 850         if (req->aborted) {
 851                 spin_unlock(&fc->lock);
 852                 fuse_copy_finish(&cs);
 853                 spin_lock(&fc->lock);
 854                 request_end(fc, req);
 855                 return -ENOENT;
 856         }
 857         /* Is it an interrupt reply? */
 858         if (req->intr_unique == oh.unique) {
 859                 err = -EINVAL;
 860                 if (nbytes != sizeof(struct fuse_out_header))
 861                         goto err_unlock;
 862
 863                 if (oh.error == -ENOSYS)
 864                         fc->no_interrupt = 1;
 865                 else if (oh.error == -EAGAIN)
 866                         queue_interrupt(fc, req);
 867
 868                 spin_unlock(&fc->lock);
 869                 fuse_copy_finish(&cs);
 870                 return nbytes;
 871         }
 872
 873         req->state = FUSE_REQ_WRITING;
 874         list_move(&req->list, &fc->io);
 875         req->out.h = oh;
 876         req->locked = 1;
 877         cs.req = req;
 878         spin_unlock(&fc->lock);
 879
 880         err = copy_out_args(&cs, &req->out, nbytes);
 881         fuse_copy_finish(&cs);
 882
 883         spin_lock(&fc->lock);
 884         req->locked = 0;
 885         if (!err) {
 886                 if (req->aborted)
 887                         err = -ENOENT;
 888         } else if (!req->aborted)
 889                 req->out.h.error = -EIO;
 890         request_end(fc, req);
 891
 892         return err ? err : nbytes;
 893
 894  err_unlock:
 895         spin_unlock(&fc->lock);
 896  err_finish:
 897         fuse_copy_finish(&cs);
 898         return err;
 899 }
 900
 901 static unsigned fuse_dev_poll(struct file *file, poll_table *wait)
 902 {
 903         unsigned mask = POLLOUT | POLLWRNORM;
 904         struct fuse_conn *fc = fuse_get_conn(file);
 905         if (!fc)
 906                 return POLLERR;
 907
 908         poll_wait(file, &fc->waitq, wait);
 909
 910         spin_lock(&fc->lock);
 911         if (!fc->connected)
 912                 mask = POLLERR;
 913         else if (request_pending(fc))
 914                 mask |= POLLIN | POLLRDNORM;
 915         spin_unlock(&fc->lock);
 916
 917         return mask;
 918 }
 919
 920 /*
 921  * Abort all requests on the given list (pending or processing)
 922  *
 923  * This function releases and reacquires fc->lock
 924  */
 925 static void end_requests(struct fuse_conn *fc, struct list_head *head)
 926 {
 927         while (!list_empty(head)) {
 928                 struct fuse_req *req;
 929                 req = list_entry(head->next, struct fuse_req, list);
 930                 req->out.h.error = -ECONNABORTED;
 931                 request_end(fc, req);
 932                 spin_lock(&fc->lock);
 933         }
 934 }
 935
 936 /*
 937  * Abort requests under I/O
 938  *
 939  * The requests are set to aborted and finished, and the request
 940  * waiter is woken up.  This will make request_wait_answer() wait
 941  * until the request is unlocked and then return.
 942  *
 943  * If the request is asynchronous, then the end function needs to be
 944  * called after waiting for the request to be unlocked (if it was
 945  * locked).
 946  */
 947 static void end_io_requests(struct fuse_conn *fc)
 948 {
 949         while (!list_empty(&fc->io)) {
 950                 struct fuse_req *req =
 951                         list_entry(fc->io.next, struct fuse_req, list);
 952                 void (*end) (struct fuse_conn *, struct fuse_req *) = req->end;
 953
 954                 req->aborted = 1;
 955                 req->out.h.error = -ECONNABORTED;
 956                 req->state = FUSE_REQ_FINISHED;
 957                 list_del_init(&req->list);
 958                 wake_up(&req->waitq);
 959                 if (end) {
 960                         req->end = NULL;
 961                         /* The end function will consume this reference */
 962                         __fuse_get_request(req);
 963                         spin_unlock(&fc->lock);
 964                         wait_event(req->waitq, !req->locked);
 965                         end(fc, req);
 966                         spin_lock(&fc->lock);
 967                 }
 968         }
 969 }
 970
 971 /*
 972  * Abort all requests.
 973  *
 974  * Emergency exit in case of a malicious or accidental deadlock, or
 975  * just a hung filesystem.
 976  *
 977  * The same effect is usually achievable through killing the
 978  * filesystem daemon and all users of the filesystem.  The exception
 979  * is the combination of an asynchronous request and the tricky
 980  * deadlock (see Documentation/filesystems/fuse.txt).
 981  *
 982  * During the aborting, progression of requests from the pending and
 983  * processing lists onto the io list, and progression of new requests
 984  * onto the pending list is prevented by req->connected being false.
 985  *
 986  * Progression of requests under I/O to the processing list is
 987  * prevented by the req->aborted flag being true for these requests.
 988  * For this reason requests on the io list must be aborted first.
 989  */
 990 void fuse_abort_conn(struct fuse_conn *fc)
 991 {
 992         spin_lock(&fc->lock);
 993         if (fc->connected) {
 994                 fc->connected = 0;
 995                 fc->blocked = 0;
 996                 end_io_requests(fc);
 997                 end_requests(fc, &fc->pending);
 998                 end_requests(fc, &fc->processing);
 999                 wake_up_all(&fc->waitq);
1000                 wake_up_all(&fc->blocked_waitq);
1001                 kill_fasync(&fc->fasync, SIGIO, POLL_IN);
1002         }
1003         spin_unlock(&fc->lock);
1004 }
1005
1006 static int fuse_dev_release(struct inode *inode, struct file *file)
1007 {
1008         struct fuse_conn *fc = fuse_get_conn(file);
1009         if (fc) {
1010                 spin_lock(&fc->lock);
1011                 fc->connected = 0;
1012                 end_requests(fc, &fc->pending);
1013                 end_requests(fc, &fc->processing);
1014                 spin_unlock(&fc->lock);
1015                 fasync_helper(-1, file, 0, &fc->fasync);
1016                 fuse_conn_put(fc);
1017         }
1018
1019         return 0;
1020 }
1021
1022 static int fuse_dev_fasync(int fd, struct file *file, int on)
1023 {
1024         struct fuse_conn *fc = fuse_get_conn(file);
1025         if (!fc)
1026                 return -EPERM;
1027
1028         /* No locking - fasync_helper does its own locking */
1029         return fasync_helper(fd, file, on, &fc->fasync);
1030 }
1031
1032 const struct file_operations fuse_dev_operations = {
1033         .owner          = THIS_MODULE,
1034         .llseek         = no_llseek,
1035         .read           = do_sync_read,
1036         .aio_read       = fuse_dev_read,
1037         .write          = do_sync_write,
1038         .aio_write      = fuse_dev_write,
1039         .poll           = fuse_dev_poll,
1040         .release        = fuse_dev_release,
1041         .fasync         = fuse_dev_fasync,
1042 };
1043
1044 static struct miscdevice fuse_miscdevice = {
1045         .minor = FUSE_MINOR,
1046         .name  = "fuse",
1047         .fops = &fuse_dev_operations,
1048 };
1049
1050 int __init fuse_dev_init(void)
1051 {
1052         int err = -ENOMEM;
1053         fuse_req_cachep = kmem_cache_create("fuse_request",
1054                                             sizeof(struct fuse_req),
1055                                             0, 0, NULL);
1056         if (!fuse_req_cachep)
1057                 goto out;
1058
1059         err = misc_register(&fuse_miscdevice);
1060         if (err)
1061                 goto out_cache_clean;
1062
1063         return 0;
1064
1065  out_cache_clean:
1066         kmem_cache_destroy(fuse_req_cachep);
1067  out:
1068         return err;
1069 }
1070
1071 void fuse_dev_cleanup(void)
1072 {
1073         misc_deregister(&fuse_miscdevice);
1074         kmem_cache_destroy(fuse_req_cachep);
1075 }