fs/splice.c

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, network, direct splicing, etc and
  13  * fixing lots of bugs.
  14  *
  15  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  16  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  17  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  18  *
  19  */
  20 #include <linux/bvec.h>
  21 #include <linux/fs.h>
  22 #include <linux/file.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/splice.h>
  25 #include <linux/memcontrol.h>
  26 #include <linux/mm_inline.h>
  27 #include <linux/swap.h>
  28 #include <linux/writeback.h>
  29 #include <linux/export.h>
  30 #include <linux/syscalls.h>
  31 #include <linux/uio.h>
  32 #include <linux/security.h>
  33 #include <linux/gfp.h>
  34 #include <linux/socket.h>
  35 #include <linux/compat.h>
  36 #include <linux/sched/signal.h>
  37
  38 #include "internal.h"
  39
  40 /*
  41  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  42  * a vm helper function, it's already simplified quite a bit by the
  43  * addition of remove_mapping(). If success is returned, the caller may
  44  * attempt to reuse this page for another destination.
  45  */
  46 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  47                                      struct pipe_buffer *buf)
  48 {
  49         struct page *page = buf->page;
  50         struct address_space *mapping;
  51
  52         lock_page(page);
  53
  54         mapping = page_mapping(page);
  55         if (mapping) {
  56                 WARN_ON(!PageUptodate(page));
  57
  58                 /*
  59                  * At least for ext2 with nobh option, we need to wait on
  60                  * writeback completing on this page, since we'll remove it
  61                  * from the pagecache.  Otherwise truncate wont wait on the
  62                  * page, allowing the disk blocks to be reused by someone else
  63                  * before we actually wrote our data to them. fs corruption
  64                  * ensues.
  65                  */
  66                 wait_on_page_writeback(page);
  67
  68                 if (page_has_private(page) &&
  69                     !try_to_release_page(page, GFP_KERNEL))
  70                         goto out_unlock;
  71
  72                 /*
  73                  * If we succeeded in removing the mapping, set LRU flag
  74                  * and return good.
  75                  */
  76                 if (remove_mapping(mapping, page)) {
  77                         buf->flags |= PIPE_BUF_FLAG_LRU;
  78                         return 0;
  79                 }
  80         }
  81
  82         /*
  83          * Raced with truncate or failed to remove page from current
  84          * address space, unlock and return failure.
  85          */
  86 out_unlock:
  87         unlock_page(page);
  88         return 1;
  89 }
  90
  91 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  92                                         struct pipe_buffer *buf)
  93 {
  94         put_page(buf->page);
  95         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  96 }
  97
  98 /*
  99  * Check whether the contents of buf is OK to access. Since the content
 100  * is a page cache page, IO may be in flight.
 101  */
 102 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
 103                                        struct pipe_buffer *buf)
 104 {
 105         struct page *page = buf->page;
 106         int err;
 107
 108         if (!PageUptodate(page)) {
 109                 lock_page(page);
 110
 111                 /*
 112                  * Page got truncated/unhashed. This will cause a 0-byte
 113                  * splice, if this is the first page.
 114                  */
 115                 if (!page->mapping) {
 116                         err = -ENODATA;
 117                         goto error;
 118                 }
 119
 120                 /*
 121                  * Uh oh, read-error from disk.
 122                  */
 123                 if (!PageUptodate(page)) {
 124                         err = -EIO;
 125                         goto error;
 126                 }
 127
 128                 /*
 129                  * Page is ok afterall, we are done.
 130                  */
 131                 unlock_page(page);
 132         }
 133
 134         return 0;
 135 error:
 136         unlock_page(page);
 137         return err;
 138 }
 139
 140 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 141         .confirm = page_cache_pipe_buf_confirm,
 142         .release = page_cache_pipe_buf_release,
 143         .steal = page_cache_pipe_buf_steal,
 144         .get = generic_pipe_buf_get,
 145 };
 146
 147 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 148                                     struct pipe_buffer *buf)
 149 {
 150         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 151                 return 1;
 152
 153         buf->flags |= PIPE_BUF_FLAG_LRU;
 154         return generic_pipe_buf_steal(pipe, buf);
 155 }
 156
 157 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 158         .confirm = generic_pipe_buf_confirm,
 159         .release = page_cache_pipe_buf_release,
 160         .steal = user_page_pipe_buf_steal,
 161         .get = generic_pipe_buf_get,
 162 };
 163
 164 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 165 {
 166         smp_mb();
 167         if (waitqueue_active(&pipe->wait))
 168                 wake_up_interruptible(&pipe->wait);
 169         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 170 }
 171
 172 /**
 173  * splice_to_pipe - fill passed data into a pipe
 174  * @pipe:       pipe to fill
 175  * @spd:        data to fill
 176  *
 177  * Description:
 178  *    @spd contains a map of pages and len/offset tuples, along with
 179  *    the struct pipe_buf_operations associated with these pages. This
 180  *    function will link that data to the pipe.
 181  *
 182  */
 183 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 184                        struct splice_pipe_desc *spd)
 185 {
 186         unsigned int spd_pages = spd->nr_pages;
 187         int ret = 0, page_nr = 0;
 188
 189         if (!spd_pages)
 190                 return 0;
 191
 192         if (unlikely(!pipe->readers)) {
 193                 send_sig(SIGPIPE, current, 0);
 194                 ret = -EPIPE;
 195                 goto out;
 196         }
 197
 198         while (pipe->nrbufs < pipe->buffers) {
 199                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 200                 struct pipe_buffer *buf = pipe->bufs + newbuf;
 201
 202                 buf->page = spd->pages[page_nr];
 203                 buf->offset = spd->partial[page_nr].offset;
 204                 buf->len = spd->partial[page_nr].len;
 205                 buf->private = spd->partial[page_nr].private;
 206                 buf->ops = spd->ops;
 207                 buf->flags = 0;
 208
 209                 pipe->nrbufs++;
 210                 page_nr++;
 211                 ret += buf->len;
 212
 213                 if (!--spd->nr_pages)
 214                         break;
 215         }
 216
 217         if (!ret)
 218                 ret = -EAGAIN;
 219
 220 out:
 221         while (page_nr < spd_pages)
 222                 spd->spd_release(spd, page_nr++);
 223
 224         return ret;
 225 }
 226 EXPORT_SYMBOL_GPL(splice_to_pipe);
 227
 228 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 229 {
 230         int ret;
 231
 232         if (unlikely(!pipe->readers)) {
 233                 send_sig(SIGPIPE, current, 0);
 234                 ret = -EPIPE;
 235         } else if (pipe->nrbufs == pipe->buffers) {
 236                 ret = -EAGAIN;
 237         } else {
 238                 int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 239                 pipe->bufs[newbuf] = *buf;
 240                 pipe->nrbufs++;
 241                 return buf->len;
 242         }
 243         pipe_buf_release(pipe, buf);
 244         return ret;
 245 }
 246 EXPORT_SYMBOL(add_to_pipe);
 247
 248 /*
 249  * Check if we need to grow the arrays holding pages and partial page
 250  * descriptions.
 251  */
 252 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 253 {
 254         unsigned int buffers = READ_ONCE(pipe->buffers);
 255
 256         spd->nr_pages_max = buffers;
 257         if (buffers <= PIPE_DEF_BUFFERS)
 258                 return 0;
 259
 260         spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
 261         spd->partial = kmalloc_array(buffers, sizeof(struct partial_page),
 262                                      GFP_KERNEL);
 263
 264         if (spd->pages && spd->partial)
 265                 return 0;
 266
 267         kfree(spd->pages);
 268         kfree(spd->partial);
 269         return -ENOMEM;
 270 }
 271
 272 void splice_shrink_spd(struct splice_pipe_desc *spd)
 273 {
 274         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
 275                 return;
 276
 277         kfree(spd->pages);
 278         kfree(spd->partial);
 279 }
 280
 281 /**
 282  * generic_file_splice_read - splice data from file to a pipe
 283  * @in:         file to splice from
 284  * @ppos:       position in @in
 285  * @pipe:       pipe to splice to
 286  * @len:        number of bytes to splice
 287  * @flags:      splice modifier flags
 288  *
 289  * Description:
 290  *    Will read pages from given file and fill them into a pipe. Can be
 291  *    used as long as it has more or less sane ->read_iter().
 292  *
 293  */
 294 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 295                                  struct pipe_inode_info *pipe, size_t len,
 296                                  unsigned int flags)
 297 {
 298         struct iov_iter to;
 299         struct kiocb kiocb;
 300         int idx, ret;
 301
 302         iov_iter_pipe(&to, READ, pipe, len);
 303         idx = to.idx;
 304         init_sync_kiocb(&kiocb, in);
 305         kiocb.ki_pos = *ppos;
 306         ret = call_read_iter(in, &kiocb, &to);
 307         if (ret > 0) {
 308                 *ppos = kiocb.ki_pos;
 309                 file_accessed(in);
 310         } else if (ret < 0) {
 311                 to.idx = idx;
 312                 to.iov_offset = 0;
 313                 iov_iter_advance(&to, 0); /* to free what was emitted */
 314                 /*
 315                  * callers of ->splice_read() expect -EAGAIN on
 316                  * "can't put anything in there", rather than -EFAULT.
 317                  */
 318                 if (ret == -EFAULT)
 319                         ret = -EAGAIN;
 320         }
 321
 322         return ret;
 323 }
 324 EXPORT_SYMBOL(generic_file_splice_read);
 325
 326 const struct pipe_buf_operations default_pipe_buf_ops = {
 327         .confirm = generic_pipe_buf_confirm,
 328         .release = generic_pipe_buf_release,
 329         .steal = generic_pipe_buf_steal,
 330         .get = generic_pipe_buf_get,
 331 };
 332
 333 int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
 334                              struct pipe_buffer *buf)
 335 {
 336         return 1;
 337 }
 338
 339 /* Pipe buffer operations for a socket and similar. */
 340 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
 341         .confirm = generic_pipe_buf_confirm,
 342         .release = generic_pipe_buf_release,
 343         .steal = generic_pipe_buf_nosteal,
 344         .get = generic_pipe_buf_get,
 345 };
 346 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 347
 348 static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
 349                             unsigned long vlen, loff_t offset)
 350 {
 351         mm_segment_t old_fs;
 352         loff_t pos = offset;
 353         ssize_t res;
 354
 355         old_fs = get_fs();
 356         set_fs(KERNEL_DS);
 357         /* The cast to a user pointer is valid due to the set_fs() */
 358         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
 359         set_fs(old_fs);
 360
 361         return res;
 362 }
 363
 364 static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 365                                  struct pipe_inode_info *pipe, size_t len,
 366                                  unsigned int flags)
 367 {
 368         struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
 369         struct iov_iter to;
 370         struct page **pages;
 371         unsigned int nr_pages;
 372         size_t offset, base, copied = 0;
 373         ssize_t res;
 374         int i;
 375
 376         if (pipe->nrbufs == pipe->buffers)
 377                 return -EAGAIN;
 378
 379         /*
 380          * Try to keep page boundaries matching to source pagecache ones -
 381          * it probably won't be much help, but...
 382          */
 383         offset = *ppos & ~PAGE_MASK;
 384
 385         iov_iter_pipe(&to, READ, pipe, len + offset);
 386
 387         res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
 388         if (res <= 0)
 389                 return -ENOMEM;
 390
 391         nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
 392
 393         vec = __vec;
 394         if (nr_pages > PIPE_DEF_BUFFERS) {
 395                 vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
 396                 if (unlikely(!vec)) {
 397                         res = -ENOMEM;
 398                         goto out;
 399                 }
 400         }
 401
 402         pipe->bufs[to.idx].offset = offset;
 403         pipe->bufs[to.idx].len -= offset;
 404
 405         for (i = 0; i < nr_pages; i++) {
 406                 size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
 407                 vec[i].iov_base = page_address(pages[i]) + offset;
 408                 vec[i].iov_len = this_len;
 409                 len -= this_len;
 410                 offset = 0;
 411         }
 412
 413         res = kernel_readv(in, vec, nr_pages, *ppos);
 414         if (res > 0) {
 415                 copied = res;
 416                 *ppos += res;
 417         }
 418
 419         if (vec != __vec)
 420                 kfree(vec);
 421 out:
 422         for (i = 0; i < nr_pages; i++)
 423                 put_page(pages[i]);
 424         kvfree(pages);
 425         iov_iter_advance(&to, copied);  /* truncates and discards */
 426         return res;
 427 }
 428
 429 /*
 430  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 431  * using sendpage(). Return the number of bytes sent.
 432  */
 433 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 434                             struct pipe_buffer *buf, struct splice_desc *sd)
 435 {
 436         struct file *file = sd->u.file;
 437         loff_t pos = sd->pos;
 438         int more;
 439
 440         if (!likely(file->f_op->sendpage))
 441                 return -EINVAL;
 442
 443         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
 444
 445         if (sd->len < sd->total_len && pipe->nrbufs > 1)
 446                 more |= MSG_SENDPAGE_NOTLAST;
 447
 448         return file->f_op->sendpage(file, buf->page, buf->offset,
 449                                     sd->len, &pos, more);
 450 }
 451
 452 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 453 {
 454         smp_mb();
 455         if (waitqueue_active(&pipe->wait))
 456                 wake_up_interruptible(&pipe->wait);
 457         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 458 }
 459
 460 /**
 461  * splice_from_pipe_feed - feed available data from a pipe to a file
 462  * @pipe:       pipe to splice from
 463  * @sd:         information to @actor
 464  * @actor:      handler that splices the data
 465  *
 466  * Description:
 467  *    This function loops over the pipe and calls @actor to do the
 468  *    actual moving of a single struct pipe_buffer to the desired
 469  *    destination.  It returns when there's no more buffers left in
 470  *    the pipe or if the requested number of bytes (@sd->total_len)
 471  *    have been copied.  It returns a positive number (one) if the
 472  *    pipe needs to be filled with more data, zero if the required
 473  *    number of bytes have been copied and -errno on error.
 474  *
 475  *    This, together with splice_from_pipe_{begin,end,next}, may be
 476  *    used to implement the functionality of __splice_from_pipe() when
 477  *    locking is required around copying the pipe buffers to the
 478  *    destination.
 479  */
 480 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 481                           splice_actor *actor)
 482 {
 483         int ret;
 484
 485         while (pipe->nrbufs) {
 486                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 487
 488                 sd->len = buf->len;
 489                 if (sd->len > sd->total_len)
 490                         sd->len = sd->total_len;
 491
 492                 ret = pipe_buf_confirm(pipe, buf);
 493                 if (unlikely(ret)) {
 494                         if (ret == -ENODATA)
 495                                 ret = 0;
 496                         return ret;
 497                 }
 498
 499                 ret = actor(pipe, buf, sd);
 500                 if (ret <= 0)
 501                         return ret;
 502
 503                 buf->offset += ret;
 504                 buf->len -= ret;
 505
 506                 sd->num_spliced += ret;
 507                 sd->len -= ret;
 508                 sd->pos += ret;
 509                 sd->total_len -= ret;
 510
 511                 if (!buf->len) {
 512                         pipe_buf_release(pipe, buf);
 513                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 514                         pipe->nrbufs--;
 515                         if (pipe->files)
 516                                 sd->need_wakeup = true;
 517                 }
 518
 519                 if (!sd->total_len)
 520                         return 0;
 521         }
 522
 523         return 1;
 524 }
 525
 526 /**
 527  * splice_from_pipe_next - wait for some data to splice from
 528  * @pipe:       pipe to splice from
 529  * @sd:         information about the splice operation
 530  *
 531  * Description:
 532  *    This function will wait for some data and return a positive
 533  *    value (one) if pipe buffers are available.  It will return zero
 534  *    or -errno if no more data needs to be spliced.
 535  */
 536 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 537 {
 538         /*
 539          * Check for signal early to make process killable when there are
 540          * always buffers available
 541          */
 542         if (signal_pending(current))
 543                 return -ERESTARTSYS;
 544
 545         while (!pipe->nrbufs) {
 546                 if (!pipe->writers)
 547                         return 0;
 548
 549                 if (!pipe->waiting_writers && sd->num_spliced)
 550                         return 0;
 551
 552                 if (sd->flags & SPLICE_F_NONBLOCK)
 553                         return -EAGAIN;
 554
 555                 if (signal_pending(current))
 556                         return -ERESTARTSYS;
 557
 558                 if (sd->need_wakeup) {
 559                         wakeup_pipe_writers(pipe);
 560                         sd->need_wakeup = false;
 561                 }
 562
 563                 pipe_wait(pipe);
 564         }
 565
 566         return 1;
 567 }
 568
 569 /**
 570  * splice_from_pipe_begin - start splicing from pipe
 571  * @sd:         information about the splice operation
 572  *
 573  * Description:
 574  *    This function should be called before a loop containing
 575  *    splice_from_pipe_next() and splice_from_pipe_feed() to
 576  *    initialize the necessary fields of @sd.
 577  */
 578 static void splice_from_pipe_begin(struct splice_desc *sd)
 579 {
 580         sd->num_spliced = 0;
 581         sd->need_wakeup = false;
 582 }
 583
 584 /**
 585  * splice_from_pipe_end - finish splicing from pipe
 586  * @pipe:       pipe to splice from
 587  * @sd:         information about the splice operation
 588  *
 589  * Description:
 590  *    This function will wake up pipe writers if necessary.  It should
 591  *    be called after a loop containing splice_from_pipe_next() and
 592  *    splice_from_pipe_feed().
 593  */
 594 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 595 {
 596         if (sd->need_wakeup)
 597                 wakeup_pipe_writers(pipe);
 598 }
 599
 600 /**
 601  * __splice_from_pipe - splice data from a pipe to given actor
 602  * @pipe:       pipe to splice from
 603  * @sd:         information to @actor
 604  * @actor:      handler that splices the data
 605  *
 606  * Description:
 607  *    This function does little more than loop over the pipe and call
 608  *    @actor to do the actual moving of a single struct pipe_buffer to
 609  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 610  *    pipe_to_user.
 611  *
 612  */
 613 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 614                            splice_actor *actor)
 615 {
 616         int ret;
 617
 618         splice_from_pipe_begin(sd);
 619         do {
 620                 cond_resched();
 621                 ret = splice_from_pipe_next(pipe, sd);
 622                 if (ret > 0)
 623                         ret = splice_from_pipe_feed(pipe, sd, actor);
 624         } while (ret > 0);
 625         splice_from_pipe_end(pipe, sd);
 626
 627         return sd->num_spliced ? sd->num_spliced : ret;
 628 }
 629 EXPORT_SYMBOL(__splice_from_pipe);
 630
 631 /**
 632  * splice_from_pipe - splice data from a pipe to a file
 633  * @pipe:       pipe to splice from
 634  * @out:        file to splice to
 635  * @ppos:       position in @out
 636  * @len:        how many bytes to splice
 637  * @flags:      splice modifier flags
 638  * @actor:      handler that splices the data
 639  *
 640  * Description:
 641  *    See __splice_from_pipe. This function locks the pipe inode,
 642  *    otherwise it's identical to __splice_from_pipe().
 643  *
 644  */
 645 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 646                          loff_t *ppos, size_t len, unsigned int flags,
 647                          splice_actor *actor)
 648 {
 649         ssize_t ret;
 650         struct splice_desc sd = {
 651                 .total_len = len,
 652                 .flags = flags,
 653                 .pos = *ppos,
 654                 .u.file = out,
 655         };
 656
 657         pipe_lock(pipe);
 658         ret = __splice_from_pipe(pipe, &sd, actor);
 659         pipe_unlock(pipe);
 660
 661         return ret;
 662 }
 663
 664 /**
 665  * iter_file_splice_write - splice data from a pipe to a file
 666  * @pipe:       pipe info
 667  * @out:        file to write to
 668  * @ppos:       position in @out
 669  * @len:        number of bytes to splice
 670  * @flags:      splice modifier flags
 671  *
 672  * Description:
 673  *    Will either move or copy pages (determined by @flags options) from
 674  *    the given pipe inode to the given file.
 675  *    This one is ->write_iter-based.
 676  *
 677  */
 678 ssize_t
 679 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 680                           loff_t *ppos, size_t len, unsigned int flags)
 681 {
 682         struct splice_desc sd = {
 683                 .total_len = len,
 684                 .flags = flags,
 685                 .pos = *ppos,
 686                 .u.file = out,
 687         };
 688         int nbufs = pipe->buffers;
 689         struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
 690                                         GFP_KERNEL);
 691         ssize_t ret;
 692
 693         if (unlikely(!array))
 694                 return -ENOMEM;
 695
 696         pipe_lock(pipe);
 697
 698         splice_from_pipe_begin(&sd);
 699         while (sd.total_len) {
 700                 struct iov_iter from;
 701                 size_t left;
 702                 int n, idx;
 703
 704                 ret = splice_from_pipe_next(pipe, &sd);
 705                 if (ret <= 0)
 706                         break;
 707
 708                 if (unlikely(nbufs < pipe->buffers)) {
 709                         kfree(array);
 710                         nbufs = pipe->buffers;
 711                         array = kcalloc(nbufs, sizeof(struct bio_vec),
 712                                         GFP_KERNEL);
 713                         if (!array) {
 714                                 ret = -ENOMEM;
 715                                 break;
 716                         }
 717                 }
 718
 719                 /* build the vector */
 720                 left = sd.total_len;
 721                 for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
 722                         struct pipe_buffer *buf = pipe->bufs + idx;
 723                         size_t this_len = buf->len;
 724
 725                         if (this_len > left)
 726                                 this_len = left;
 727
 728                         if (idx == pipe->buffers - 1)
 729                                 idx = -1;
 730
 731                         ret = pipe_buf_confirm(pipe, buf);
 732                         if (unlikely(ret)) {
 733                                 if (ret == -ENODATA)
 734                                         ret = 0;
 735                                 goto done;
 736                         }
 737
 738                         array[n].bv_page = buf->page;
 739                         array[n].bv_len = this_len;
 740                         array[n].bv_offset = buf->offset;
 741                         left -= this_len;
 742                 }
 743
 744                 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
 745                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
 746                 if (ret <= 0)
 747                         break;
 748
 749                 sd.num_spliced += ret;
 750                 sd.total_len -= ret;
 751                 *ppos = sd.pos;
 752
 753                 /* dismiss the fully eaten buffers, adjust the partial one */
 754                 while (ret) {
 755                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 756                         if (ret >= buf->len) {
 757                                 ret -= buf->len;
 758                                 buf->len = 0;
 759                                 pipe_buf_release(pipe, buf);
 760                                 pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 761                                 pipe->nrbufs--;
 762                                 if (pipe->files)
 763                                         sd.need_wakeup = true;
 764                         } else {
 765                                 buf->offset += ret;
 766                                 buf->len -= ret;
 767                                 ret = 0;
 768                         }
 769                 }
 770         }
 771 done:
 772         kfree(array);
 773         splice_from_pipe_end(pipe, &sd);
 774
 775         pipe_unlock(pipe);
 776
 777         if (sd.num_spliced)
 778                 ret = sd.num_spliced;
 779
 780         return ret;
 781 }
 782
 783 EXPORT_SYMBOL(iter_file_splice_write);
 784
 785 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 786                           struct splice_desc *sd)
 787 {
 788         int ret;
 789         void *data;
 790         loff_t tmp = sd->pos;
 791
 792         data = kmap(buf->page);
 793         ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
 794         kunmap(buf->page);
 795
 796         return ret;
 797 }
 798
 799 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
 800                                          struct file *out, loff_t *ppos,
 801                                          size_t len, unsigned int flags)
 802 {
 803         ssize_t ret;
 804
 805         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
 806         if (ret > 0)
 807                 *ppos += ret;
 808
 809         return ret;
 810 }
 811
 812 /**
 813  * generic_splice_sendpage - splice data from a pipe to a socket
 814  * @pipe:       pipe to splice from
 815  * @out:        socket to write to
 816  * @ppos:       position in @out
 817  * @len:        number of bytes to splice
 818  * @flags:      splice modifier flags
 819  *
 820  * Description:
 821  *    Will send @len bytes from the pipe to a network socket. No data copying
 822  *    is involved.
 823  *
 824  */
 825 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 826                                 loff_t *ppos, size_t len, unsigned int flags)
 827 {
 828         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 829 }
 830
 831 EXPORT_SYMBOL(generic_splice_sendpage);
 832
 833 /*
 834  * Attempt to initiate a splice from pipe to file.
 835  */
 836 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 837                            loff_t *ppos, size_t len, unsigned int flags)
 838 {
 839         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
 840                                 loff_t *, size_t, unsigned int);
 841
 842         if (out->f_op->splice_write)
 843                 splice_write = out->f_op->splice_write;
 844         else
 845                 splice_write = default_file_splice_write;
 846
 847         return splice_write(pipe, out, ppos, len, flags);
 848 }
 849
 850 /*
 851  * Attempt to initiate a splice from a file to a pipe.
 852  */
 853 static long do_splice_to(struct file *in, loff_t *ppos,
 854                          struct pipe_inode_info *pipe, size_t len,
 855                          unsigned int flags)
 856 {
 857         ssize_t (*splice_read)(struct file *, loff_t *,
 858                                struct pipe_inode_info *, size_t, unsigned int);
 859         int ret;
 860
 861         if (unlikely(!(in->f_mode & FMODE_READ)))
 862                 return -EBADF;
 863
 864         ret = rw_verify_area(READ, in, ppos, len);
 865         if (unlikely(ret < 0))
 866                 return ret;
 867
 868         if (unlikely(len > MAX_RW_COUNT))
 869                 len = MAX_RW_COUNT;
 870
 871         if (in->f_op->splice_read)
 872                 splice_read = in->f_op->splice_read;
 873         else
 874                 splice_read = default_file_splice_read;
 875
 876         return splice_read(in, ppos, pipe, len, flags);
 877 }
 878
 879 /**
 880  * splice_direct_to_actor - splices data directly between two non-pipes
 881  * @in:         file to splice from
 882  * @sd:         actor information on where to splice to
 883  * @actor:      handles the data splicing
 884  *
 885  * Description:
 886  *    This is a special case helper to splice directly between two
 887  *    points, without requiring an explicit pipe. Internally an allocated
 888  *    pipe is cached in the process, and reused during the lifetime of
 889  *    that process.
 890  *
 891  */
 892 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 893                                splice_direct_actor *actor)
 894 {
 895         struct pipe_inode_info *pipe;
 896         long ret, bytes;
 897         umode_t i_mode;
 898         size_t len;
 899         int i, flags, more;
 900
 901         /*
 902          * We require the input being a regular file, as we don't want to
 903          * randomly drop data for eg socket -> socket splicing. Use the
 904          * piped splicing for that!
 905          */
 906         i_mode = file_inode(in)->i_mode;
 907         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 908                 return -EINVAL;
 909
 910         /*
 911          * neither in nor out is a pipe, setup an internal pipe attached to
 912          * 'out' and transfer the wanted data from 'in' to 'out' through that
 913          */
 914         pipe = current->splice_pipe;
 915         if (unlikely(!pipe)) {
 916                 pipe = alloc_pipe_info();
 917                 if (!pipe)
 918                         return -ENOMEM;
 919
 920                 /*
 921                  * We don't have an immediate reader, but we'll read the stuff
 922                  * out of the pipe right after the splice_to_pipe(). So set
 923                  * PIPE_READERS appropriately.
 924                  */
 925                 pipe->readers = 1;
 926
 927                 current->splice_pipe = pipe;
 928         }
 929
 930         /*
 931          * Do the splice.
 932          */
 933         ret = 0;
 934         bytes = 0;
 935         len = sd->total_len;
 936         flags = sd->flags;
 937
 938         /*
 939          * Don't block on output, we have to drain the direct pipe.
 940          */
 941         sd->flags &= ~SPLICE_F_NONBLOCK;
 942         more = sd->flags & SPLICE_F_MORE;
 943
 944         WARN_ON_ONCE(pipe->nrbufs != 0);
 945
 946         while (len) {
 947                 size_t read_len;
 948                 loff_t pos = sd->pos, prev_pos = pos;
 949
 950                 /* Don't try to read more the pipe has space for. */
 951                 read_len = min_t(size_t, len,
 952                                  (pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
 953                 ret = do_splice_to(in, &pos, pipe, read_len, flags);
 954                 if (unlikely(ret <= 0))
 955                         goto out_release;
 956
 957                 read_len = ret;
 958                 sd->total_len = read_len;
 959
 960                 /*
 961                  * If more data is pending, set SPLICE_F_MORE
 962                  * If this is the last data and SPLICE_F_MORE was not set
 963                  * initially, clears it.
 964                  */
 965                 if (read_len < len)
 966                         sd->flags |= SPLICE_F_MORE;
 967                 else if (!more)
 968                         sd->flags &= ~SPLICE_F_MORE;
 969                 /*
 970                  * NOTE: nonblocking mode only applies to the input. We
 971                  * must not do the output in nonblocking mode as then we
 972                  * could get stuck data in the internal pipe:
 973                  */
 974                 ret = actor(pipe, sd);
 975                 if (unlikely(ret <= 0)) {
 976                         sd->pos = prev_pos;
 977                         goto out_release;
 978                 }
 979
 980                 bytes += ret;
 981                 len -= ret;
 982                 sd->pos = pos;
 983
 984                 if (ret < read_len) {
 985                         sd->pos = prev_pos + ret;
 986                         goto out_release;
 987                 }
 988         }
 989
 990 done:
 991         pipe->nrbufs = pipe->curbuf = 0;
 992         file_accessed(in);
 993         return bytes;
 994
 995 out_release:
 996         /*
 997          * If we did an incomplete transfer we must release
 998          * the pipe buffers in question:
 999          */
1000         for (i = 0; i < pipe->buffers; i++) {
1001                 struct pipe_buffer *buf = pipe->bufs + i;
1002
1003                 if (buf->ops)
1004                         pipe_buf_release(pipe, buf);
1005         }
1006
1007         if (!bytes)
1008                 bytes = ret;
1009
1010         goto done;
1011 }
1012 EXPORT_SYMBOL(splice_direct_to_actor);
1013
1014 static int direct_splice_actor(struct pipe_inode_info *pipe,
1015                                struct splice_desc *sd)
1016 {
1017         struct file *file = sd->u.file;
1018
1019         return do_splice_from(pipe, file, sd->opos, sd->total_len,
1020                               sd->flags);
1021 }
1022
1023 /**
1024  * do_splice_direct - splices data directly between two files
1025  * @in:         file to splice from
1026  * @ppos:       input file offset
1027  * @out:        file to splice to
1028  * @opos:       output file offset
1029  * @len:        number of bytes to splice
1030  * @flags:      splice modifier flags
1031  *
1032  * Description:
1033  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1034  *    doing it in the application would incur an extra system call
1035  *    (splice in + splice out, as compared to just sendfile()). So this helper
1036  *    can splice directly through a process-private pipe.
1037  *
1038  */
1039 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1040                       loff_t *opos, size_t len, unsigned int flags)
1041 {
1042         struct splice_desc sd = {
1043                 .len            = len,
1044                 .total_len      = len,
1045                 .flags          = flags,
1046                 .pos            = *ppos,
1047                 .u.file         = out,
1048                 .opos           = opos,
1049         };
1050         long ret;
1051
1052         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1053                 return -EBADF;
1054
1055         if (unlikely(out->f_flags & O_APPEND))
1056                 return -EINVAL;
1057
1058         ret = rw_verify_area(WRITE, out, opos, len);
1059         if (unlikely(ret < 0))
1060                 return ret;
1061
1062         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1063         if (ret > 0)
1064                 *ppos = sd.pos;
1065
1066         return ret;
1067 }
1068 EXPORT_SYMBOL(do_splice_direct);
1069
1070 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
1071 {
1072         for (;;) {
1073                 if (unlikely(!pipe->readers)) {
1074                         send_sig(SIGPIPE, current, 0);
1075                         return -EPIPE;
1076                 }
1077                 if (pipe->nrbufs != pipe->buffers)
1078                         return 0;
1079                 if (flags & SPLICE_F_NONBLOCK)
1080                         return -EAGAIN;
1081                 if (signal_pending(current))
1082                         return -ERESTARTSYS;
1083                 pipe->waiting_writers++;
1084                 pipe_wait(pipe);
1085                 pipe->waiting_writers--;
1086         }
1087 }
1088
1089 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1090                                struct pipe_inode_info *opipe,
1091                                size_t len, unsigned int flags);
1092
1093 /*
1094  * Determine where to splice to/from.
1095  */
1096 static long do_splice(struct file *in, loff_t __user *off_in,
1097                       struct file *out, loff_t __user *off_out,
1098                       size_t len, unsigned int flags)
1099 {
1100         struct pipe_inode_info *ipipe;
1101         struct pipe_inode_info *opipe;
1102         loff_t offset;
1103         long ret;
1104
1105         ipipe = get_pipe_info(in);
1106         opipe = get_pipe_info(out);
1107
1108         if (ipipe && opipe) {
1109                 if (off_in || off_out)
1110                         return -ESPIPE;
1111
1112                 if (!(in->f_mode & FMODE_READ))
1113                         return -EBADF;
1114
1115                 if (!(out->f_mode & FMODE_WRITE))
1116                         return -EBADF;
1117
1118                 /* Splicing to self would be fun, but... */
1119                 if (ipipe == opipe)
1120                         return -EINVAL;
1121
1122                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1123                         flags |= SPLICE_F_NONBLOCK;
1124
1125                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1126         }
1127
1128         if (ipipe) {
1129                 if (off_in)
1130                         return -ESPIPE;
1131                 if (off_out) {
1132                         if (!(out->f_mode & FMODE_PWRITE))
1133                                 return -EINVAL;
1134                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1135                                 return -EFAULT;
1136                 } else {
1137                         offset = out->f_pos;
1138                 }
1139
1140                 if (unlikely(!(out->f_mode & FMODE_WRITE)))
1141                         return -EBADF;
1142
1143                 if (unlikely(out->f_flags & O_APPEND))
1144                         return -EINVAL;
1145
1146                 ret = rw_verify_area(WRITE, out, &offset, len);
1147                 if (unlikely(ret < 0))
1148                         return ret;
1149
1150                 if (in->f_flags & O_NONBLOCK)
1151                         flags |= SPLICE_F_NONBLOCK;
1152
1153                 file_start_write(out);
1154                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1155                 file_end_write(out);
1156
1157                 if (!off_out)
1158                         out->f_pos = offset;
1159                 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1160                         ret = -EFAULT;
1161
1162                 return ret;
1163         }
1164
1165         if (opipe) {
1166                 if (off_out)
1167                         return -ESPIPE;
1168                 if (off_in) {
1169                         if (!(in->f_mode & FMODE_PREAD))
1170                                 return -EINVAL;
1171                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1172                                 return -EFAULT;
1173                 } else {
1174                         offset = in->f_pos;
1175                 }
1176
1177                 if (out->f_flags & O_NONBLOCK)
1178                         flags |= SPLICE_F_NONBLOCK;
1179
1180                 pipe_lock(opipe);
1181                 ret = wait_for_space(opipe, flags);
1182                 if (!ret)
1183                         ret = do_splice_to(in, &offset, opipe, len, flags);
1184                 pipe_unlock(opipe);
1185                 if (ret > 0)
1186                         wakeup_pipe_readers(opipe);
1187                 if (!off_in)
1188                         in->f_pos = offset;
1189                 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1190                         ret = -EFAULT;
1191
1192                 return ret;
1193         }
1194
1195         return -EINVAL;
1196 }
1197
1198 static int iter_to_pipe(struct iov_iter *from,
1199                         struct pipe_inode_info *pipe,
1200                         unsigned flags)
1201 {
1202         struct pipe_buffer buf = {
1203                 .ops = &user_page_pipe_buf_ops,
1204                 .flags = flags
1205         };
1206         size_t total = 0;
1207         int ret = 0;
1208         bool failed = false;
1209
1210         while (iov_iter_count(from) && !failed) {
1211                 struct page *pages[16];
1212                 ssize_t copied;
1213                 size_t start;
1214                 int n;
1215
1216                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1217                 if (copied <= 0) {
1218                         ret = copied;
1219                         break;
1220                 }
1221
1222                 for (n = 0; copied; n++, start = 0) {
1223                         int size = min_t(int, copied, PAGE_SIZE - start);
1224                         if (!failed) {
1225                                 buf.page = pages[n];
1226                                 buf.offset = start;
1227                                 buf.len = size;
1228                                 ret = add_to_pipe(pipe, &buf);
1229                                 if (unlikely(ret < 0)) {
1230                                         failed = true;
1231                                 } else {
1232                                         iov_iter_advance(from, ret);
1233                                         total += ret;
1234                                 }
1235                         } else {
1236                                 put_page(pages[n]);
1237                         }
1238                         copied -= size;
1239                 }
1240         }
1241         return total ? total : ret;
1242 }
1243
1244 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1245                         struct splice_desc *sd)
1246 {
1247         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1248         return n == sd->len ? n : -EFAULT;
1249 }
1250
1251 /*
1252  * For lack of a better implementation, implement vmsplice() to userspace
1253  * as a simple copy of the pipes pages to the user iov.
1254  */
1255 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1256                              unsigned int flags)
1257 {
1258         struct pipe_inode_info *pipe = get_pipe_info(file);
1259         struct splice_desc sd = {
1260                 .total_len = iov_iter_count(iter),
1261                 .flags = flags,
1262                 .u.data = iter
1263         };
1264         long ret = 0;
1265
1266         if (!pipe)
1267                 return -EBADF;
1268
1269         if (sd.total_len) {
1270                 pipe_lock(pipe);
1271                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1272                 pipe_unlock(pipe);
1273         }
1274
1275         return ret;
1276 }
1277
1278 /*
1279  * vmsplice splices a user address range into a pipe. It can be thought of
1280  * as splice-from-memory, where the regular splice is splice-from-file (or
1281  * to file). In both cases the output is a pipe, naturally.
1282  */
1283 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1284                              unsigned int flags)
1285 {
1286         struct pipe_inode_info *pipe;
1287         long ret = 0;
1288         unsigned buf_flag = 0;
1289
1290         if (flags & SPLICE_F_GIFT)
1291                 buf_flag = PIPE_BUF_FLAG_GIFT;
1292
1293         pipe = get_pipe_info(file);
1294         if (!pipe)
1295                 return -EBADF;
1296
1297         pipe_lock(pipe);
1298         ret = wait_for_space(pipe, flags);
1299         if (!ret)
1300                 ret = iter_to_pipe(iter, pipe, buf_flag);
1301         pipe_unlock(pipe);
1302         if (ret > 0)
1303                 wakeup_pipe_readers(pipe);
1304         return ret;
1305 }
1306
1307 static int vmsplice_type(struct fd f, int *type)
1308 {
1309         if (!f.file)
1310                 return -EBADF;
1311         if (f.file->f_mode & FMODE_WRITE) {
1312                 *type = WRITE;
1313         } else if (f.file->f_mode & FMODE_READ) {
1314                 *type = READ;
1315         } else {
1316                 fdput(f);
1317                 return -EBADF;
1318         }
1319         return 0;
1320 }
1321
1322 /*
1323  * Note that vmsplice only really supports true splicing _from_ user memory
1324  * to a pipe, not the other way around. Splicing from user memory is a simple
1325  * operation that can be supported without any funky alignment restrictions
1326  * or nasty vm tricks. We simply map in the user memory and fill them into
1327  * a pipe. The reverse isn't quite as easy, though. There are two possible
1328  * solutions for that:
1329  *
1330  *      - memcpy() the data internally, at which point we might as well just
1331  *        do a regular read() on the buffer anyway.
1332  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1333  *        has restriction limitations on both ends of the pipe).
1334  *
1335  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1336  *
1337  */
1338 static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
1339 {
1340         if (unlikely(flags & ~SPLICE_F_ALL))
1341                 return -EINVAL;
1342
1343         if (!iov_iter_count(iter))
1344                 return 0;
1345
1346         if (iov_iter_rw(iter) == WRITE)
1347                 return vmsplice_to_pipe(f, iter, flags);
1348         else
1349                 return vmsplice_to_user(f, iter, flags);
1350 }
1351
1352 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1353                 unsigned long, nr_segs, unsigned int, flags)
1354 {
1355         struct iovec iovstack[UIO_FASTIOV];
1356         struct iovec *iov = iovstack;
1357         struct iov_iter iter;
1358         long error;
1359         struct fd f;
1360         int type;
1361
1362         f = fdget(fd);
1363         error = vmsplice_type(f, &type);
1364         if (error)
1365                 return error;
1366
1367         error = import_iovec(type, uiov, nr_segs,
1368                              ARRAY_SIZE(iovstack), &iov, &iter);
1369         if (!error) {
1370                 error = do_vmsplice(f.file, &iter, flags);
1371                 kfree(iov);
1372         }
1373         fdput(f);
1374         return error;
1375 }
1376
1377 #ifdef CONFIG_COMPAT
1378 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1379                     unsigned int, nr_segs, unsigned int, flags)
1380 {
1381         struct iovec iovstack[UIO_FASTIOV];
1382         struct iovec *iov = iovstack;
1383         struct iov_iter iter;
1384         long error;
1385         struct fd f;
1386         int type;
1387
1388         f = fdget(fd);
1389         error = vmsplice_type(f, &type);
1390         if (error)
1391                 return error;
1392
1393         error = compat_import_iovec(type, iov32, nr_segs,
1394                              ARRAY_SIZE(iovstack), &iov, &iter);
1395         if (!error) {
1396                 error = do_vmsplice(f.file, &iter, flags);
1397                 kfree(iov);
1398         }
1399         fdput(f);
1400         return error;
1401 }
1402 #endif
1403
1404 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1405                 int, fd_out, loff_t __user *, off_out,
1406                 size_t, len, unsigned int, flags)
1407 {
1408         struct fd in, out;
1409         long error;
1410
1411         if (unlikely(!len))
1412                 return 0;
1413
1414         if (unlikely(flags & ~SPLICE_F_ALL))
1415                 return -EINVAL;
1416
1417         error = -EBADF;
1418         in = fdget(fd_in);
1419         if (in.file) {
1420                 if (in.file->f_mode & FMODE_READ) {
1421                         out = fdget(fd_out);
1422                         if (out.file) {
1423                                 if (out.file->f_mode & FMODE_WRITE)
1424                                         error = do_splice(in.file, off_in,
1425                                                           out.file, off_out,
1426                                                           len, flags);
1427                                 fdput(out);
1428                         }
1429                 }
1430                 fdput(in);
1431         }
1432         return error;
1433 }
1434
1435 /*
1436  * Make sure there's data to read. Wait for input if we can, otherwise
1437  * return an appropriate error.
1438  */
1439 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1440 {
1441         int ret;
1442
1443         /*
1444          * Check ->nrbufs without the inode lock first. This function
1445          * is speculative anyways, so missing one is ok.
1446          */
1447         if (pipe->nrbufs)
1448                 return 0;
1449
1450         ret = 0;
1451         pipe_lock(pipe);
1452
1453         while (!pipe->nrbufs) {
1454                 if (signal_pending(current)) {
1455                         ret = -ERESTARTSYS;
1456                         break;
1457                 }
1458                 if (!pipe->writers)
1459                         break;
1460                 if (!pipe->waiting_writers) {
1461                         if (flags & SPLICE_F_NONBLOCK) {
1462                                 ret = -EAGAIN;
1463                                 break;
1464                         }
1465                 }
1466                 pipe_wait(pipe);
1467         }
1468
1469         pipe_unlock(pipe);
1470         return ret;
1471 }
1472
1473 /*
1474  * Make sure there's writeable room. Wait for room if we can, otherwise
1475  * return an appropriate error.
1476  */
1477 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1478 {
1479         int ret;
1480
1481         /*
1482          * Check ->nrbufs without the inode lock first. This function
1483          * is speculative anyways, so missing one is ok.
1484          */
1485         if (pipe->nrbufs < pipe->buffers)
1486                 return 0;
1487
1488         ret = 0;
1489         pipe_lock(pipe);
1490
1491         while (pipe->nrbufs >= pipe->buffers) {
1492                 if (!pipe->readers) {
1493                         send_sig(SIGPIPE, current, 0);
1494                         ret = -EPIPE;
1495                         break;
1496                 }
1497                 if (flags & SPLICE_F_NONBLOCK) {
1498                         ret = -EAGAIN;
1499                         break;
1500                 }
1501                 if (signal_pending(current)) {
1502                         ret = -ERESTARTSYS;
1503                         break;
1504                 }
1505                 pipe->waiting_writers++;
1506                 pipe_wait(pipe);
1507                 pipe->waiting_writers--;
1508         }
1509
1510         pipe_unlock(pipe);
1511         return ret;
1512 }
1513
1514 /*
1515  * Splice contents of ipipe to opipe.
1516  */
1517 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1518                                struct pipe_inode_info *opipe,
1519                                size_t len, unsigned int flags)
1520 {
1521         struct pipe_buffer *ibuf, *obuf;
1522         int ret = 0, nbuf;
1523         bool input_wakeup = false;
1524
1525
1526 retry:
1527         ret = ipipe_prep(ipipe, flags);
1528         if (ret)
1529                 return ret;
1530
1531         ret = opipe_prep(opipe, flags);
1532         if (ret)
1533                 return ret;
1534
1535         /*
1536          * Potential ABBA deadlock, work around it by ordering lock
1537          * grabbing by pipe info address. Otherwise two different processes
1538          * could deadlock (one doing tee from A -> B, the other from B -> A).
1539          */
1540         pipe_double_lock(ipipe, opipe);
1541
1542         do {
1543                 if (!opipe->readers) {
1544                         send_sig(SIGPIPE, current, 0);
1545                         if (!ret)
1546                                 ret = -EPIPE;
1547                         break;
1548                 }
1549
1550                 if (!ipipe->nrbufs && !ipipe->writers)
1551                         break;
1552
1553                 /*
1554                  * Cannot make any progress, because either the input
1555                  * pipe is empty or the output pipe is full.
1556                  */
1557                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1558                         /* Already processed some buffers, break */
1559                         if (ret)
1560                                 break;
1561
1562                         if (flags & SPLICE_F_NONBLOCK) {
1563                                 ret = -EAGAIN;
1564                                 break;
1565                         }
1566
1567                         /*
1568                          * We raced with another reader/writer and haven't
1569                          * managed to process any buffers.  A zero return
1570                          * value means EOF, so retry instead.
1571                          */
1572                         pipe_unlock(ipipe);
1573                         pipe_unlock(opipe);
1574                         goto retry;
1575                 }
1576
1577                 ibuf = ipipe->bufs + ipipe->curbuf;
1578                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1579                 obuf = opipe->bufs + nbuf;
1580
1581                 if (len >= ibuf->len) {
1582                         /*
1583                          * Simply move the whole buffer from ipipe to opipe
1584                          */
1585                         *obuf = *ibuf;
1586                         ibuf->ops = NULL;
1587                         opipe->nrbufs++;
1588                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1589                         ipipe->nrbufs--;
1590                         input_wakeup = true;
1591                 } else {
1592                         /*
1593                          * Get a reference to this pipe buffer,
1594                          * so we can copy the contents over.
1595                          */
1596                         if (!pipe_buf_get(ipipe, ibuf)) {
1597                                 if (ret == 0)
1598                                         ret = -EFAULT;
1599                                 break;
1600                         }
1601                         *obuf = *ibuf;
1602
1603                         /*
1604                          * Don't inherit the gift flag, we need to
1605                          * prevent multiple steals of this page.
1606                          */
1607                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1608
1609                         pipe_buf_mark_unmergeable(obuf);
1610
1611                         obuf->len = len;
1612                         opipe->nrbufs++;
1613                         ibuf->offset += obuf->len;
1614                         ibuf->len -= obuf->len;
1615                 }
1616                 ret += obuf->len;
1617                 len -= obuf->len;
1618         } while (len);
1619
1620         pipe_unlock(ipipe);
1621         pipe_unlock(opipe);
1622
1623         /*
1624          * If we put data in the output pipe, wakeup any potential readers.
1625          */
1626         if (ret > 0)
1627                 wakeup_pipe_readers(opipe);
1628
1629         if (input_wakeup)
1630                 wakeup_pipe_writers(ipipe);
1631
1632         return ret;
1633 }
1634
1635 /*
1636  * Link contents of ipipe to opipe.
1637  */
1638 static int link_pipe(struct pipe_inode_info *ipipe,
1639                      struct pipe_inode_info *opipe,
1640                      size_t len, unsigned int flags)
1641 {
1642         struct pipe_buffer *ibuf, *obuf;
1643         int ret = 0, i = 0, nbuf;
1644
1645         /*
1646          * Potential ABBA deadlock, work around it by ordering lock
1647          * grabbing by pipe info address. Otherwise two different processes
1648          * could deadlock (one doing tee from A -> B, the other from B -> A).
1649          */
1650         pipe_double_lock(ipipe, opipe);
1651
1652         do {
1653                 if (!opipe->readers) {
1654                         send_sig(SIGPIPE, current, 0);
1655                         if (!ret)
1656                                 ret = -EPIPE;
1657                         break;
1658                 }
1659
1660                 /*
1661                  * If we have iterated all input buffers or ran out of
1662                  * output room, break.
1663                  */
1664                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1665                         break;
1666
1667                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1668                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1669
1670                 /*
1671                  * Get a reference to this pipe buffer,
1672                  * so we can copy the contents over.
1673                  */
1674                 if (!pipe_buf_get(ipipe, ibuf)) {
1675                         if (ret == 0)
1676                                 ret = -EFAULT;
1677                         break;
1678                 }
1679
1680                 obuf = opipe->bufs + nbuf;
1681                 *obuf = *ibuf;
1682
1683                 /*
1684                  * Don't inherit the gift flag, we need to
1685                  * prevent multiple steals of this page.
1686                  */
1687                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1688
1689                 pipe_buf_mark_unmergeable(obuf);
1690
1691                 if (obuf->len > len)
1692                         obuf->len = len;
1693
1694                 opipe->nrbufs++;
1695                 ret += obuf->len;
1696                 len -= obuf->len;
1697                 i++;
1698         } while (len);
1699
1700         /*
1701          * return EAGAIN if we have the potential of some data in the
1702          * future, otherwise just return 0
1703          */
1704         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1705                 ret = -EAGAIN;
1706
1707         pipe_unlock(ipipe);
1708         pipe_unlock(opipe);
1709
1710         /*
1711          * If we put data in the output pipe, wakeup any potential readers.
1712          */
1713         if (ret > 0)
1714                 wakeup_pipe_readers(opipe);
1715
1716         return ret;
1717 }
1718
1719 /*
1720  * This is a tee(1) implementation that works on pipes. It doesn't copy
1721  * any data, it simply references the 'in' pages on the 'out' pipe.
1722  * The 'flags' used are the SPLICE_F_* variants, currently the only
1723  * applicable one is SPLICE_F_NONBLOCK.
1724  */
1725 static long do_tee(struct file *in, struct file *out, size_t len,
1726                    unsigned int flags)
1727 {
1728         struct pipe_inode_info *ipipe = get_pipe_info(in);
1729         struct pipe_inode_info *opipe = get_pipe_info(out);
1730         int ret = -EINVAL;
1731
1732         /*
1733          * Duplicate the contents of ipipe to opipe without actually
1734          * copying the data.
1735          */
1736         if (ipipe && opipe && ipipe != opipe) {
1737                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1738                         flags |= SPLICE_F_NONBLOCK;
1739
1740                 /*
1741                  * Keep going, unless we encounter an error. The ipipe/opipe
1742                  * ordering doesn't really matter.
1743                  */
1744                 ret = ipipe_prep(ipipe, flags);
1745                 if (!ret) {
1746                         ret = opipe_prep(opipe, flags);
1747                         if (!ret)
1748                                 ret = link_pipe(ipipe, opipe, len, flags);
1749                 }
1750         }
1751
1752         return ret;
1753 }
1754
1755 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1756 {
1757         struct fd in;
1758         int error;
1759
1760         if (unlikely(flags & ~SPLICE_F_ALL))
1761                 return -EINVAL;
1762
1763         if (unlikely(!len))
1764                 return 0;
1765
1766         error = -EBADF;
1767         in = fdget(fdin);
1768         if (in.file) {
1769                 if (in.file->f_mode & FMODE_READ) {
1770                         struct fd out = fdget(fdout);
1771                         if (out.file) {
1772                                 if (out.file->f_mode & FMODE_WRITE)
1773                                         error = do_tee(in.file, out.file,
1774                                                         len, flags);
1775                                 fdput(out);
1776                         }
1777                 }
1778                 fdput(in);
1779         }
1780
1781         return error;
1782 }