fs/splice.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * "splice": joining two ropes together by interweaving their strands.
   4  *
   5  * This is the "extended pipe" functionality, where a pipe is used as
   6  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   7  * buffer that you can use to transfer data from one end to the other.
   8  *
   9  * The traditional unix read/write is extended with a "splice()" operation
  10  * that transfers data buffers to or from a pipe buffer.
  11  *
  12  * Named by Larry McVoy, original implementation from Linus, extended by
  13  * Jens to support splicing to files, network, direct splicing, etc and
  14  * fixing lots of bugs.
  15  *
  16  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  17  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  18  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  19  *
  20  */
  21 #include <linux/bvec.h>
  22 #include <linux/fs.h>
  23 #include <linux/file.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/splice.h>
  26 #include <linux/memcontrol.h>
  27 #include <linux/mm_inline.h>
  28 #include <linux/swap.h>
  29 #include <linux/writeback.h>
  30 #include <linux/export.h>
  31 #include <linux/syscalls.h>
  32 #include <linux/uio.h>
  33 #include <linux/security.h>
  34 #include <linux/gfp.h>
  35 #include <linux/socket.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 bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe,
  47                 struct pipe_buffer *buf)
  48 {
  49         struct folio *folio = page_folio(buf->page);
  50         struct address_space *mapping;
  51
  52         folio_lock(folio);
  53
  54         mapping = folio_mapping(folio);
  55         if (mapping) {
  56                 WARN_ON(!folio_test_uptodate(folio));
  57
  58                 /*
  59                  * At least for ext2 with nobh option, we need to wait on
  60                  * writeback completing on this folio, since we'll remove it
  61                  * from the pagecache.  Otherwise truncate wont wait on the
  62                  * folio, 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                 folio_wait_writeback(folio);
  67
  68                 if (folio_has_private(folio) &&
  69                     !filemap_release_folio(folio, 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, folio)) {
  77                         buf->flags |= PIPE_BUF_FLAG_LRU;
  78                         return true;
  79                 }
  80         }
  81
  82         /*
  83          * Raced with truncate or failed to remove folio from current
  84          * address space, unlock and return failure.
  85          */
  86 out_unlock:
  87         folio_unlock(folio);
  88         return false;
  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         .try_steal      = page_cache_pipe_buf_try_steal,
 144         .get            = generic_pipe_buf_get,
 145 };
 146
 147 static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 148                 struct pipe_buffer *buf)
 149 {
 150         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 151                 return false;
 152
 153         buf->flags |= PIPE_BUF_FLAG_LRU;
 154         return generic_pipe_buf_try_steal(pipe, buf);
 155 }
 156
 157 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 158         .release        = page_cache_pipe_buf_release,
 159         .try_steal      = user_page_pipe_buf_try_steal,
 160         .get            = generic_pipe_buf_get,
 161 };
 162
 163 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 164 {
 165         smp_mb();
 166         if (waitqueue_active(&pipe->rd_wait))
 167                 wake_up_interruptible(&pipe->rd_wait);
 168         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 169 }
 170
 171 /**
 172  * splice_to_pipe - fill passed data into a pipe
 173  * @pipe:       pipe to fill
 174  * @spd:        data to fill
 175  *
 176  * Description:
 177  *    @spd contains a map of pages and len/offset tuples, along with
 178  *    the struct pipe_buf_operations associated with these pages. This
 179  *    function will link that data to the pipe.
 180  *
 181  */
 182 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 183                        struct splice_pipe_desc *spd)
 184 {
 185         unsigned int spd_pages = spd->nr_pages;
 186         unsigned int tail = pipe->tail;
 187         unsigned int head = pipe->head;
 188         unsigned int mask = pipe->ring_size - 1;
 189         int ret = 0, page_nr = 0;
 190
 191         if (!spd_pages)
 192                 return 0;
 193
 194         if (unlikely(!pipe->readers)) {
 195                 send_sig(SIGPIPE, current, 0);
 196                 ret = -EPIPE;
 197                 goto out;
 198         }
 199
 200         while (!pipe_full(head, tail, pipe->max_usage)) {
 201                 struct pipe_buffer *buf = &pipe->bufs[head & mask];
 202
 203                 buf->page = spd->pages[page_nr];
 204                 buf->offset = spd->partial[page_nr].offset;
 205                 buf->len = spd->partial[page_nr].len;
 206                 buf->private = spd->partial[page_nr].private;
 207                 buf->ops = spd->ops;
 208                 buf->flags = 0;
 209
 210                 head++;
 211                 pipe->head = head;
 212                 page_nr++;
 213                 ret += buf->len;
 214
 215                 if (!--spd->nr_pages)
 216                         break;
 217         }
 218
 219         if (!ret)
 220                 ret = -EAGAIN;
 221
 222 out:
 223         while (page_nr < spd_pages)
 224                 spd->spd_release(spd, page_nr++);
 225
 226         return ret;
 227 }
 228 EXPORT_SYMBOL_GPL(splice_to_pipe);
 229
 230 ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 231 {
 232         unsigned int head = pipe->head;
 233         unsigned int tail = pipe->tail;
 234         unsigned int mask = pipe->ring_size - 1;
 235         int ret;
 236
 237         if (unlikely(!pipe->readers)) {
 238                 send_sig(SIGPIPE, current, 0);
 239                 ret = -EPIPE;
 240         } else if (pipe_full(head, tail, pipe->max_usage)) {
 241                 ret = -EAGAIN;
 242         } else {
 243                 pipe->bufs[head & mask] = *buf;
 244                 pipe->head = head + 1;
 245                 return buf->len;
 246         }
 247         pipe_buf_release(pipe, buf);
 248         return ret;
 249 }
 250 EXPORT_SYMBOL(add_to_pipe);
 251
 252 /*
 253  * Check if we need to grow the arrays holding pages and partial page
 254  * descriptions.
 255  */
 256 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 257 {
 258         unsigned int max_usage = READ_ONCE(pipe->max_usage);
 259
 260         spd->nr_pages_max = max_usage;
 261         if (max_usage <= PIPE_DEF_BUFFERS)
 262                 return 0;
 263
 264         spd->pages = kmalloc_array(max_usage, sizeof(struct page *), GFP_KERNEL);
 265         spd->partial = kmalloc_array(max_usage, sizeof(struct partial_page),
 266                                      GFP_KERNEL);
 267
 268         if (spd->pages && spd->partial)
 269                 return 0;
 270
 271         kfree(spd->pages);
 272         kfree(spd->partial);
 273         return -ENOMEM;
 274 }
 275
 276 void splice_shrink_spd(struct splice_pipe_desc *spd)
 277 {
 278         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
 279                 return;
 280
 281         kfree(spd->pages);
 282         kfree(spd->partial);
 283 }
 284
 285 /**
 286  * generic_file_splice_read - splice data from file to a pipe
 287  * @in:         file to splice from
 288  * @ppos:       position in @in
 289  * @pipe:       pipe to splice to
 290  * @len:        number of bytes to splice
 291  * @flags:      splice modifier flags
 292  *
 293  * Description:
 294  *    Will read pages from given file and fill them into a pipe. Can be
 295  *    used as long as it has more or less sane ->read_iter().
 296  *
 297  */
 298 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 299                                  struct pipe_inode_info *pipe, size_t len,
 300                                  unsigned int flags)
 301 {
 302         struct iov_iter to;
 303         struct kiocb kiocb;
 304         unsigned int i_head;
 305         int ret;
 306
 307         iov_iter_pipe(&to, READ, pipe, len);
 308         i_head = to.head;
 309         init_sync_kiocb(&kiocb, in);
 310         kiocb.ki_pos = *ppos;
 311         ret = call_read_iter(in, &kiocb, &to);
 312         if (ret > 0) {
 313                 *ppos = kiocb.ki_pos;
 314                 file_accessed(in);
 315         } else if (ret < 0) {
 316                 to.head = i_head;
 317                 to.iov_offset = 0;
 318                 iov_iter_advance(&to, 0); /* to free what was emitted */
 319                 /*
 320                  * callers of ->splice_read() expect -EAGAIN on
 321                  * "can't put anything in there", rather than -EFAULT.
 322                  */
 323                 if (ret == -EFAULT)
 324                         ret = -EAGAIN;
 325         }
 326
 327         return ret;
 328 }
 329 EXPORT_SYMBOL(generic_file_splice_read);
 330
 331 const struct pipe_buf_operations default_pipe_buf_ops = {
 332         .release        = generic_pipe_buf_release,
 333         .try_steal      = generic_pipe_buf_try_steal,
 334         .get            = generic_pipe_buf_get,
 335 };
 336
 337 /* Pipe buffer operations for a socket and similar. */
 338 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
 339         .release        = generic_pipe_buf_release,
 340         .get            = generic_pipe_buf_get,
 341 };
 342 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 343
 344 /*
 345  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 346  * using sendpage(). Return the number of bytes sent.
 347  */
 348 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 349                             struct pipe_buffer *buf, struct splice_desc *sd)
 350 {
 351         struct file *file = sd->u.file;
 352         loff_t pos = sd->pos;
 353         int more;
 354
 355         if (!likely(file->f_op->sendpage))
 356                 return -EINVAL;
 357
 358         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
 359
 360         if (sd->len < sd->total_len &&
 361             pipe_occupancy(pipe->head, pipe->tail) > 1)
 362                 more |= MSG_SENDPAGE_NOTLAST;
 363
 364         return file->f_op->sendpage(file, buf->page, buf->offset,
 365                                     sd->len, &pos, more);
 366 }
 367
 368 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 369 {
 370         smp_mb();
 371         if (waitqueue_active(&pipe->wr_wait))
 372                 wake_up_interruptible(&pipe->wr_wait);
 373         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 374 }
 375
 376 /**
 377  * splice_from_pipe_feed - feed available data from a pipe to a file
 378  * @pipe:       pipe to splice from
 379  * @sd:         information to @actor
 380  * @actor:      handler that splices the data
 381  *
 382  * Description:
 383  *    This function loops over the pipe and calls @actor to do the
 384  *    actual moving of a single struct pipe_buffer to the desired
 385  *    destination.  It returns when there's no more buffers left in
 386  *    the pipe or if the requested number of bytes (@sd->total_len)
 387  *    have been copied.  It returns a positive number (one) if the
 388  *    pipe needs to be filled with more data, zero if the required
 389  *    number of bytes have been copied and -errno on error.
 390  *
 391  *    This, together with splice_from_pipe_{begin,end,next}, may be
 392  *    used to implement the functionality of __splice_from_pipe() when
 393  *    locking is required around copying the pipe buffers to the
 394  *    destination.
 395  */
 396 static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 397                           splice_actor *actor)
 398 {
 399         unsigned int head = pipe->head;
 400         unsigned int tail = pipe->tail;
 401         unsigned int mask = pipe->ring_size - 1;
 402         int ret;
 403
 404         while (!pipe_empty(head, tail)) {
 405                 struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 406
 407                 sd->len = buf->len;
 408                 if (sd->len > sd->total_len)
 409                         sd->len = sd->total_len;
 410
 411                 ret = pipe_buf_confirm(pipe, buf);
 412                 if (unlikely(ret)) {
 413                         if (ret == -ENODATA)
 414                                 ret = 0;
 415                         return ret;
 416                 }
 417
 418                 ret = actor(pipe, buf, sd);
 419                 if (ret <= 0)
 420                         return ret;
 421
 422                 buf->offset += ret;
 423                 buf->len -= ret;
 424
 425                 sd->num_spliced += ret;
 426                 sd->len -= ret;
 427                 sd->pos += ret;
 428                 sd->total_len -= ret;
 429
 430                 if (!buf->len) {
 431                         pipe_buf_release(pipe, buf);
 432                         tail++;
 433                         pipe->tail = tail;
 434                         if (pipe->files)
 435                                 sd->need_wakeup = true;
 436                 }
 437
 438                 if (!sd->total_len)
 439                         return 0;
 440         }
 441
 442         return 1;
 443 }
 444
 445 /* We know we have a pipe buffer, but maybe it's empty? */
 446 static inline bool eat_empty_buffer(struct pipe_inode_info *pipe)
 447 {
 448         unsigned int tail = pipe->tail;
 449         unsigned int mask = pipe->ring_size - 1;
 450         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 451
 452         if (unlikely(!buf->len)) {
 453                 pipe_buf_release(pipe, buf);
 454                 pipe->tail = tail+1;
 455                 return true;
 456         }
 457
 458         return false;
 459 }
 460
 461 /**
 462  * splice_from_pipe_next - wait for some data to splice from
 463  * @pipe:       pipe to splice from
 464  * @sd:         information about the splice operation
 465  *
 466  * Description:
 467  *    This function will wait for some data and return a positive
 468  *    value (one) if pipe buffers are available.  It will return zero
 469  *    or -errno if no more data needs to be spliced.
 470  */
 471 static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 472 {
 473         /*
 474          * Check for signal early to make process killable when there are
 475          * always buffers available
 476          */
 477         if (signal_pending(current))
 478                 return -ERESTARTSYS;
 479
 480 repeat:
 481         while (pipe_empty(pipe->head, pipe->tail)) {
 482                 if (!pipe->writers)
 483                         return 0;
 484
 485                 if (sd->num_spliced)
 486                         return 0;
 487
 488                 if (sd->flags & SPLICE_F_NONBLOCK)
 489                         return -EAGAIN;
 490
 491                 if (signal_pending(current))
 492                         return -ERESTARTSYS;
 493
 494                 if (sd->need_wakeup) {
 495                         wakeup_pipe_writers(pipe);
 496                         sd->need_wakeup = false;
 497                 }
 498
 499                 pipe_wait_readable(pipe);
 500         }
 501
 502         if (eat_empty_buffer(pipe))
 503                 goto repeat;
 504
 505         return 1;
 506 }
 507
 508 /**
 509  * splice_from_pipe_begin - start splicing from pipe
 510  * @sd:         information about the splice operation
 511  *
 512  * Description:
 513  *    This function should be called before a loop containing
 514  *    splice_from_pipe_next() and splice_from_pipe_feed() to
 515  *    initialize the necessary fields of @sd.
 516  */
 517 static void splice_from_pipe_begin(struct splice_desc *sd)
 518 {
 519         sd->num_spliced = 0;
 520         sd->need_wakeup = false;
 521 }
 522
 523 /**
 524  * splice_from_pipe_end - finish splicing from pipe
 525  * @pipe:       pipe to splice from
 526  * @sd:         information about the splice operation
 527  *
 528  * Description:
 529  *    This function will wake up pipe writers if necessary.  It should
 530  *    be called after a loop containing splice_from_pipe_next() and
 531  *    splice_from_pipe_feed().
 532  */
 533 static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 534 {
 535         if (sd->need_wakeup)
 536                 wakeup_pipe_writers(pipe);
 537 }
 538
 539 /**
 540  * __splice_from_pipe - splice data from a pipe to given actor
 541  * @pipe:       pipe to splice from
 542  * @sd:         information to @actor
 543  * @actor:      handler that splices the data
 544  *
 545  * Description:
 546  *    This function does little more than loop over the pipe and call
 547  *    @actor to do the actual moving of a single struct pipe_buffer to
 548  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 549  *    pipe_to_user.
 550  *
 551  */
 552 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 553                            splice_actor *actor)
 554 {
 555         int ret;
 556
 557         splice_from_pipe_begin(sd);
 558         do {
 559                 cond_resched();
 560                 ret = splice_from_pipe_next(pipe, sd);
 561                 if (ret > 0)
 562                         ret = splice_from_pipe_feed(pipe, sd, actor);
 563         } while (ret > 0);
 564         splice_from_pipe_end(pipe, sd);
 565
 566         return sd->num_spliced ? sd->num_spliced : ret;
 567 }
 568 EXPORT_SYMBOL(__splice_from_pipe);
 569
 570 /**
 571  * splice_from_pipe - splice data from a pipe to a file
 572  * @pipe:       pipe to splice from
 573  * @out:        file to splice to
 574  * @ppos:       position in @out
 575  * @len:        how many bytes to splice
 576  * @flags:      splice modifier flags
 577  * @actor:      handler that splices the data
 578  *
 579  * Description:
 580  *    See __splice_from_pipe. This function locks the pipe inode,
 581  *    otherwise it's identical to __splice_from_pipe().
 582  *
 583  */
 584 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 585                          loff_t *ppos, size_t len, unsigned int flags,
 586                          splice_actor *actor)
 587 {
 588         ssize_t ret;
 589         struct splice_desc sd = {
 590                 .total_len = len,
 591                 .flags = flags,
 592                 .pos = *ppos,
 593                 .u.file = out,
 594         };
 595
 596         pipe_lock(pipe);
 597         ret = __splice_from_pipe(pipe, &sd, actor);
 598         pipe_unlock(pipe);
 599
 600         return ret;
 601 }
 602
 603 /**
 604  * iter_file_splice_write - splice data from a pipe to a file
 605  * @pipe:       pipe info
 606  * @out:        file to write to
 607  * @ppos:       position in @out
 608  * @len:        number of bytes to splice
 609  * @flags:      splice modifier flags
 610  *
 611  * Description:
 612  *    Will either move or copy pages (determined by @flags options) from
 613  *    the given pipe inode to the given file.
 614  *    This one is ->write_iter-based.
 615  *
 616  */
 617 ssize_t
 618 iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 619                           loff_t *ppos, size_t len, unsigned int flags)
 620 {
 621         struct splice_desc sd = {
 622                 .total_len = len,
 623                 .flags = flags,
 624                 .pos = *ppos,
 625                 .u.file = out,
 626         };
 627         int nbufs = pipe->max_usage;
 628         struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
 629                                         GFP_KERNEL);
 630         ssize_t ret;
 631
 632         if (unlikely(!array))
 633                 return -ENOMEM;
 634
 635         pipe_lock(pipe);
 636
 637         splice_from_pipe_begin(&sd);
 638         while (sd.total_len) {
 639                 struct iov_iter from;
 640                 unsigned int head, tail, mask;
 641                 size_t left;
 642                 int n;
 643
 644                 ret = splice_from_pipe_next(pipe, &sd);
 645                 if (ret <= 0)
 646                         break;
 647
 648                 if (unlikely(nbufs < pipe->max_usage)) {
 649                         kfree(array);
 650                         nbufs = pipe->max_usage;
 651                         array = kcalloc(nbufs, sizeof(struct bio_vec),
 652                                         GFP_KERNEL);
 653                         if (!array) {
 654                                 ret = -ENOMEM;
 655                                 break;
 656                         }
 657                 }
 658
 659                 head = pipe->head;
 660                 tail = pipe->tail;
 661                 mask = pipe->ring_size - 1;
 662
 663                 /* build the vector */
 664                 left = sd.total_len;
 665                 for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) {
 666                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 667                         size_t this_len = buf->len;
 668
 669                         /* zero-length bvecs are not supported, skip them */
 670                         if (!this_len)
 671                                 continue;
 672                         this_len = min(this_len, left);
 673
 674                         ret = pipe_buf_confirm(pipe, buf);
 675                         if (unlikely(ret)) {
 676                                 if (ret == -ENODATA)
 677                                         ret = 0;
 678                                 goto done;
 679                         }
 680
 681                         array[n].bv_page = buf->page;
 682                         array[n].bv_len = this_len;
 683                         array[n].bv_offset = buf->offset;
 684                         left -= this_len;
 685                         n++;
 686                 }
 687
 688                 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
 689                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
 690                 if (ret <= 0)
 691                         break;
 692
 693                 sd.num_spliced += ret;
 694                 sd.total_len -= ret;
 695                 *ppos = sd.pos;
 696
 697                 /* dismiss the fully eaten buffers, adjust the partial one */
 698                 tail = pipe->tail;
 699                 while (ret) {
 700                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 701                         if (ret >= buf->len) {
 702                                 ret -= buf->len;
 703                                 buf->len = 0;
 704                                 pipe_buf_release(pipe, buf);
 705                                 tail++;
 706                                 pipe->tail = tail;
 707                                 if (pipe->files)
 708                                         sd.need_wakeup = true;
 709                         } else {
 710                                 buf->offset += ret;
 711                                 buf->len -= ret;
 712                                 ret = 0;
 713                         }
 714                 }
 715         }
 716 done:
 717         kfree(array);
 718         splice_from_pipe_end(pipe, &sd);
 719
 720         pipe_unlock(pipe);
 721
 722         if (sd.num_spliced)
 723                 ret = sd.num_spliced;
 724
 725         return ret;
 726 }
 727
 728 EXPORT_SYMBOL(iter_file_splice_write);
 729
 730 /**
 731  * generic_splice_sendpage - splice data from a pipe to a socket
 732  * @pipe:       pipe to splice from
 733  * @out:        socket to write to
 734  * @ppos:       position in @out
 735  * @len:        number of bytes to splice
 736  * @flags:      splice modifier flags
 737  *
 738  * Description:
 739  *    Will send @len bytes from the pipe to a network socket. No data copying
 740  *    is involved.
 741  *
 742  */
 743 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 744                                 loff_t *ppos, size_t len, unsigned int flags)
 745 {
 746         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 747 }
 748
 749 EXPORT_SYMBOL(generic_splice_sendpage);
 750
 751 static int warn_unsupported(struct file *file, const char *op)
 752 {
 753         pr_debug_ratelimited(
 754                 "splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
 755                 op, file, current->pid, current->comm);
 756         return -EINVAL;
 757 }
 758
 759 /*
 760  * Attempt to initiate a splice from pipe to file.
 761  */
 762 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 763                            loff_t *ppos, size_t len, unsigned int flags)
 764 {
 765         if (unlikely(!out->f_op->splice_write))
 766                 return warn_unsupported(out, "write");
 767         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 768 }
 769
 770 /*
 771  * Attempt to initiate a splice from a file to a pipe.
 772  */
 773 static long do_splice_to(struct file *in, loff_t *ppos,
 774                          struct pipe_inode_info *pipe, size_t len,
 775                          unsigned int flags)
 776 {
 777         unsigned int p_space;
 778         int ret;
 779
 780         if (unlikely(!(in->f_mode & FMODE_READ)))
 781                 return -EBADF;
 782
 783         /* Don't try to read more the pipe has space for. */
 784         p_space = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail);
 785         len = min_t(size_t, len, p_space << PAGE_SHIFT);
 786
 787         ret = rw_verify_area(READ, in, ppos, len);
 788         if (unlikely(ret < 0))
 789                 return ret;
 790
 791         if (unlikely(len > MAX_RW_COUNT))
 792                 len = MAX_RW_COUNT;
 793
 794         if (unlikely(!in->f_op->splice_read))
 795                 return warn_unsupported(in, "read");
 796         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 797 }
 798
 799 /**
 800  * splice_direct_to_actor - splices data directly between two non-pipes
 801  * @in:         file to splice from
 802  * @sd:         actor information on where to splice to
 803  * @actor:      handles the data splicing
 804  *
 805  * Description:
 806  *    This is a special case helper to splice directly between two
 807  *    points, without requiring an explicit pipe. Internally an allocated
 808  *    pipe is cached in the process, and reused during the lifetime of
 809  *    that process.
 810  *
 811  */
 812 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 813                                splice_direct_actor *actor)
 814 {
 815         struct pipe_inode_info *pipe;
 816         long ret, bytes;
 817         umode_t i_mode;
 818         size_t len;
 819         int i, flags, more;
 820
 821         /*
 822          * We require the input being a regular file, as we don't want to
 823          * randomly drop data for eg socket -> socket splicing. Use the
 824          * piped splicing for that!
 825          */
 826         i_mode = file_inode(in)->i_mode;
 827         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 828                 return -EINVAL;
 829
 830         /*
 831          * neither in nor out is a pipe, setup an internal pipe attached to
 832          * 'out' and transfer the wanted data from 'in' to 'out' through that
 833          */
 834         pipe = current->splice_pipe;
 835         if (unlikely(!pipe)) {
 836                 pipe = alloc_pipe_info();
 837                 if (!pipe)
 838                         return -ENOMEM;
 839
 840                 /*
 841                  * We don't have an immediate reader, but we'll read the stuff
 842                  * out of the pipe right after the splice_to_pipe(). So set
 843                  * PIPE_READERS appropriately.
 844                  */
 845                 pipe->readers = 1;
 846
 847                 current->splice_pipe = pipe;
 848         }
 849
 850         /*
 851          * Do the splice.
 852          */
 853         ret = 0;
 854         bytes = 0;
 855         len = sd->total_len;
 856         flags = sd->flags;
 857
 858         /*
 859          * Don't block on output, we have to drain the direct pipe.
 860          */
 861         sd->flags &= ~SPLICE_F_NONBLOCK;
 862         more = sd->flags & SPLICE_F_MORE;
 863
 864         WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail));
 865
 866         while (len) {
 867                 size_t read_len;
 868                 loff_t pos = sd->pos, prev_pos = pos;
 869
 870                 ret = do_splice_to(in, &pos, pipe, len, flags);
 871                 if (unlikely(ret <= 0))
 872                         goto out_release;
 873
 874                 read_len = ret;
 875                 sd->total_len = read_len;
 876
 877                 /*
 878                  * If more data is pending, set SPLICE_F_MORE
 879                  * If this is the last data and SPLICE_F_MORE was not set
 880                  * initially, clears it.
 881                  */
 882                 if (read_len < len)
 883                         sd->flags |= SPLICE_F_MORE;
 884                 else if (!more)
 885                         sd->flags &= ~SPLICE_F_MORE;
 886                 /*
 887                  * NOTE: nonblocking mode only applies to the input. We
 888                  * must not do the output in nonblocking mode as then we
 889                  * could get stuck data in the internal pipe:
 890                  */
 891                 ret = actor(pipe, sd);
 892                 if (unlikely(ret <= 0)) {
 893                         sd->pos = prev_pos;
 894                         goto out_release;
 895                 }
 896
 897                 bytes += ret;
 898                 len -= ret;
 899                 sd->pos = pos;
 900
 901                 if (ret < read_len) {
 902                         sd->pos = prev_pos + ret;
 903                         goto out_release;
 904                 }
 905         }
 906
 907 done:
 908         pipe->tail = pipe->head = 0;
 909         file_accessed(in);
 910         return bytes;
 911
 912 out_release:
 913         /*
 914          * If we did an incomplete transfer we must release
 915          * the pipe buffers in question:
 916          */
 917         for (i = 0; i < pipe->ring_size; i++) {
 918                 struct pipe_buffer *buf = &pipe->bufs[i];
 919
 920                 if (buf->ops)
 921                         pipe_buf_release(pipe, buf);
 922         }
 923
 924         if (!bytes)
 925                 bytes = ret;
 926
 927         goto done;
 928 }
 929 EXPORT_SYMBOL(splice_direct_to_actor);
 930
 931 static int direct_splice_actor(struct pipe_inode_info *pipe,
 932                                struct splice_desc *sd)
 933 {
 934         struct file *file = sd->u.file;
 935
 936         return do_splice_from(pipe, file, sd->opos, sd->total_len,
 937                               sd->flags);
 938 }
 939
 940 /**
 941  * do_splice_direct - splices data directly between two files
 942  * @in:         file to splice from
 943  * @ppos:       input file offset
 944  * @out:        file to splice to
 945  * @opos:       output file offset
 946  * @len:        number of bytes to splice
 947  * @flags:      splice modifier flags
 948  *
 949  * Description:
 950  *    For use by do_sendfile(). splice can easily emulate sendfile, but
 951  *    doing it in the application would incur an extra system call
 952  *    (splice in + splice out, as compared to just sendfile()). So this helper
 953  *    can splice directly through a process-private pipe.
 954  *
 955  */
 956 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 957                       loff_t *opos, size_t len, unsigned int flags)
 958 {
 959         struct splice_desc sd = {
 960                 .len            = len,
 961                 .total_len      = len,
 962                 .flags          = flags,
 963                 .pos            = *ppos,
 964                 .u.file         = out,
 965                 .opos           = opos,
 966         };
 967         long ret;
 968
 969         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 970                 return -EBADF;
 971
 972         if (unlikely(out->f_flags & O_APPEND))
 973                 return -EINVAL;
 974
 975         ret = rw_verify_area(WRITE, out, opos, len);
 976         if (unlikely(ret < 0))
 977                 return ret;
 978
 979         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
 980         if (ret > 0)
 981                 *ppos = sd.pos;
 982
 983         return ret;
 984 }
 985 EXPORT_SYMBOL(do_splice_direct);
 986
 987 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
 988 {
 989         for (;;) {
 990                 if (unlikely(!pipe->readers)) {
 991                         send_sig(SIGPIPE, current, 0);
 992                         return -EPIPE;
 993                 }
 994                 if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 995                         return 0;
 996                 if (flags & SPLICE_F_NONBLOCK)
 997                         return -EAGAIN;
 998                 if (signal_pending(current))
 999                         return -ERESTARTSYS;
1000                 pipe_wait_writable(pipe);
1001         }
1002 }
1003
1004 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1005                                struct pipe_inode_info *opipe,
1006                                size_t len, unsigned int flags);
1007
1008 long splice_file_to_pipe(struct file *in,
1009                          struct pipe_inode_info *opipe,
1010                          loff_t *offset,
1011                          size_t len, unsigned int flags)
1012 {
1013         long ret;
1014
1015         pipe_lock(opipe);
1016         ret = wait_for_space(opipe, flags);
1017         if (!ret)
1018                 ret = do_splice_to(in, offset, opipe, len, flags);
1019         pipe_unlock(opipe);
1020         if (ret > 0)
1021                 wakeup_pipe_readers(opipe);
1022         return ret;
1023 }
1024
1025 /*
1026  * Determine where to splice to/from.
1027  */
1028 long do_splice(struct file *in, loff_t *off_in, struct file *out,
1029                loff_t *off_out, size_t len, unsigned int flags)
1030 {
1031         struct pipe_inode_info *ipipe;
1032         struct pipe_inode_info *opipe;
1033         loff_t offset;
1034         long ret;
1035
1036         if (unlikely(!(in->f_mode & FMODE_READ) ||
1037                      !(out->f_mode & FMODE_WRITE)))
1038                 return -EBADF;
1039
1040         ipipe = get_pipe_info(in, true);
1041         opipe = get_pipe_info(out, true);
1042
1043         if (ipipe && opipe) {
1044                 if (off_in || off_out)
1045                         return -ESPIPE;
1046
1047                 /* Splicing to self would be fun, but... */
1048                 if (ipipe == opipe)
1049                         return -EINVAL;
1050
1051                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1052                         flags |= SPLICE_F_NONBLOCK;
1053
1054                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1055         }
1056
1057         if (ipipe) {
1058                 if (off_in)
1059                         return -ESPIPE;
1060                 if (off_out) {
1061                         if (!(out->f_mode & FMODE_PWRITE))
1062                                 return -EINVAL;
1063                         offset = *off_out;
1064                 } else {
1065                         offset = out->f_pos;
1066                 }
1067
1068                 if (unlikely(out->f_flags & O_APPEND))
1069                         return -EINVAL;
1070
1071                 ret = rw_verify_area(WRITE, out, &offset, len);
1072                 if (unlikely(ret < 0))
1073                         return ret;
1074
1075                 if (in->f_flags & O_NONBLOCK)
1076                         flags |= SPLICE_F_NONBLOCK;
1077
1078                 file_start_write(out);
1079                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1080                 file_end_write(out);
1081
1082                 if (!off_out)
1083                         out->f_pos = offset;
1084                 else
1085                         *off_out = offset;
1086
1087                 return ret;
1088         }
1089
1090         if (opipe) {
1091                 if (off_out)
1092                         return -ESPIPE;
1093                 if (off_in) {
1094                         if (!(in->f_mode & FMODE_PREAD))
1095                                 return -EINVAL;
1096                         offset = *off_in;
1097                 } else {
1098                         offset = in->f_pos;
1099                 }
1100
1101                 if (out->f_flags & O_NONBLOCK)
1102                         flags |= SPLICE_F_NONBLOCK;
1103
1104                 ret = splice_file_to_pipe(in, opipe, &offset, len, flags);
1105                 if (!off_in)
1106                         in->f_pos = offset;
1107                 else
1108                         *off_in = offset;
1109
1110                 return ret;
1111         }
1112
1113         return -EINVAL;
1114 }
1115
1116 static long __do_splice(struct file *in, loff_t __user *off_in,
1117                         struct file *out, loff_t __user *off_out,
1118                         size_t len, unsigned int flags)
1119 {
1120         struct pipe_inode_info *ipipe;
1121         struct pipe_inode_info *opipe;
1122         loff_t offset, *__off_in = NULL, *__off_out = NULL;
1123         long ret;
1124
1125         ipipe = get_pipe_info(in, true);
1126         opipe = get_pipe_info(out, true);
1127
1128         if (ipipe && off_in)
1129                 return -ESPIPE;
1130         if (opipe && off_out)
1131                 return -ESPIPE;
1132
1133         if (off_out) {
1134                 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1135                         return -EFAULT;
1136                 __off_out = &offset;
1137         }
1138         if (off_in) {
1139                 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1140                         return -EFAULT;
1141                 __off_in = &offset;
1142         }
1143
1144         ret = do_splice(in, __off_in, out, __off_out, len, flags);
1145         if (ret < 0)
1146                 return ret;
1147
1148         if (__off_out && copy_to_user(off_out, __off_out, sizeof(loff_t)))
1149                 return -EFAULT;
1150         if (__off_in && copy_to_user(off_in, __off_in, sizeof(loff_t)))
1151                 return -EFAULT;
1152
1153         return ret;
1154 }
1155
1156 static int iter_to_pipe(struct iov_iter *from,
1157                         struct pipe_inode_info *pipe,
1158                         unsigned flags)
1159 {
1160         struct pipe_buffer buf = {
1161                 .ops = &user_page_pipe_buf_ops,
1162                 .flags = flags
1163         };
1164         size_t total = 0;
1165         int ret = 0;
1166         bool failed = false;
1167
1168         while (iov_iter_count(from) && !failed) {
1169                 struct page *pages[16];
1170                 ssize_t copied;
1171                 size_t start;
1172                 int n;
1173
1174                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1175                 if (copied <= 0) {
1176                         ret = copied;
1177                         break;
1178                 }
1179
1180                 for (n = 0; copied; n++, start = 0) {
1181                         int size = min_t(int, copied, PAGE_SIZE - start);
1182                         if (!failed) {
1183                                 buf.page = pages[n];
1184                                 buf.offset = start;
1185                                 buf.len = size;
1186                                 ret = add_to_pipe(pipe, &buf);
1187                                 if (unlikely(ret < 0)) {
1188                                         failed = true;
1189                                 } else {
1190                                         iov_iter_advance(from, ret);
1191                                         total += ret;
1192                                 }
1193                         } else {
1194                                 put_page(pages[n]);
1195                         }
1196                         copied -= size;
1197                 }
1198         }
1199         return total ? total : ret;
1200 }
1201
1202 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1203                         struct splice_desc *sd)
1204 {
1205         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1206         return n == sd->len ? n : -EFAULT;
1207 }
1208
1209 /*
1210  * For lack of a better implementation, implement vmsplice() to userspace
1211  * as a simple copy of the pipes pages to the user iov.
1212  */
1213 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1214                              unsigned int flags)
1215 {
1216         struct pipe_inode_info *pipe = get_pipe_info(file, true);
1217         struct splice_desc sd = {
1218                 .total_len = iov_iter_count(iter),
1219                 .flags = flags,
1220                 .u.data = iter
1221         };
1222         long ret = 0;
1223
1224         if (!pipe)
1225                 return -EBADF;
1226
1227         if (sd.total_len) {
1228                 pipe_lock(pipe);
1229                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1230                 pipe_unlock(pipe);
1231         }
1232
1233         return ret;
1234 }
1235
1236 /*
1237  * vmsplice splices a user address range into a pipe. It can be thought of
1238  * as splice-from-memory, where the regular splice is splice-from-file (or
1239  * to file). In both cases the output is a pipe, naturally.
1240  */
1241 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1242                              unsigned int flags)
1243 {
1244         struct pipe_inode_info *pipe;
1245         long ret = 0;
1246         unsigned buf_flag = 0;
1247
1248         if (flags & SPLICE_F_GIFT)
1249                 buf_flag = PIPE_BUF_FLAG_GIFT;
1250
1251         pipe = get_pipe_info(file, true);
1252         if (!pipe)
1253                 return -EBADF;
1254
1255         pipe_lock(pipe);
1256         ret = wait_for_space(pipe, flags);
1257         if (!ret)
1258                 ret = iter_to_pipe(iter, pipe, buf_flag);
1259         pipe_unlock(pipe);
1260         if (ret > 0)
1261                 wakeup_pipe_readers(pipe);
1262         return ret;
1263 }
1264
1265 static int vmsplice_type(struct fd f, int *type)
1266 {
1267         if (!f.file)
1268                 return -EBADF;
1269         if (f.file->f_mode & FMODE_WRITE) {
1270                 *type = WRITE;
1271         } else if (f.file->f_mode & FMODE_READ) {
1272                 *type = READ;
1273         } else {
1274                 fdput(f);
1275                 return -EBADF;
1276         }
1277         return 0;
1278 }
1279
1280 /*
1281  * Note that vmsplice only really supports true splicing _from_ user memory
1282  * to a pipe, not the other way around. Splicing from user memory is a simple
1283  * operation that can be supported without any funky alignment restrictions
1284  * or nasty vm tricks. We simply map in the user memory and fill them into
1285  * a pipe. The reverse isn't quite as easy, though. There are two possible
1286  * solutions for that:
1287  *
1288  *      - memcpy() the data internally, at which point we might as well just
1289  *        do a regular read() on the buffer anyway.
1290  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1291  *        has restriction limitations on both ends of the pipe).
1292  *
1293  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1294  *
1295  */
1296 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1297                 unsigned long, nr_segs, unsigned int, flags)
1298 {
1299         struct iovec iovstack[UIO_FASTIOV];
1300         struct iovec *iov = iovstack;
1301         struct iov_iter iter;
1302         ssize_t error;
1303         struct fd f;
1304         int type;
1305
1306         if (unlikely(flags & ~SPLICE_F_ALL))
1307                 return -EINVAL;
1308
1309         f = fdget(fd);
1310         error = vmsplice_type(f, &type);
1311         if (error)
1312                 return error;
1313
1314         error = import_iovec(type, uiov, nr_segs,
1315                              ARRAY_SIZE(iovstack), &iov, &iter);
1316         if (error < 0)
1317                 goto out_fdput;
1318
1319         if (!iov_iter_count(&iter))
1320                 error = 0;
1321         else if (iov_iter_rw(&iter) == WRITE)
1322                 error = vmsplice_to_pipe(f.file, &iter, flags);
1323         else
1324                 error = vmsplice_to_user(f.file, &iter, flags);
1325
1326         kfree(iov);
1327 out_fdput:
1328         fdput(f);
1329         return error;
1330 }
1331
1332 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1333                 int, fd_out, loff_t __user *, off_out,
1334                 size_t, len, unsigned int, flags)
1335 {
1336         struct fd in, out;
1337         long error;
1338
1339         if (unlikely(!len))
1340                 return 0;
1341
1342         if (unlikely(flags & ~SPLICE_F_ALL))
1343                 return -EINVAL;
1344
1345         error = -EBADF;
1346         in = fdget(fd_in);
1347         if (in.file) {
1348                 out = fdget(fd_out);
1349                 if (out.file) {
1350                         error = __do_splice(in.file, off_in, out.file, off_out,
1351                                                 len, flags);
1352                         fdput(out);
1353                 }
1354                 fdput(in);
1355         }
1356         return error;
1357 }
1358
1359 /*
1360  * Make sure there's data to read. Wait for input if we can, otherwise
1361  * return an appropriate error.
1362  */
1363 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1364 {
1365         int ret;
1366
1367         /*
1368          * Check the pipe occupancy without the inode lock first. This function
1369          * is speculative anyways, so missing one is ok.
1370          */
1371         if (!pipe_empty(pipe->head, pipe->tail))
1372                 return 0;
1373
1374         ret = 0;
1375         pipe_lock(pipe);
1376
1377         while (pipe_empty(pipe->head, pipe->tail)) {
1378                 if (signal_pending(current)) {
1379                         ret = -ERESTARTSYS;
1380                         break;
1381                 }
1382                 if (!pipe->writers)
1383                         break;
1384                 if (flags & SPLICE_F_NONBLOCK) {
1385                         ret = -EAGAIN;
1386                         break;
1387                 }
1388                 pipe_wait_readable(pipe);
1389         }
1390
1391         pipe_unlock(pipe);
1392         return ret;
1393 }
1394
1395 /*
1396  * Make sure there's writeable room. Wait for room if we can, otherwise
1397  * return an appropriate error.
1398  */
1399 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1400 {
1401         int ret;
1402
1403         /*
1404          * Check pipe occupancy without the inode lock first. This function
1405          * is speculative anyways, so missing one is ok.
1406          */
1407         if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
1408                 return 0;
1409
1410         ret = 0;
1411         pipe_lock(pipe);
1412
1413         while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
1414                 if (!pipe->readers) {
1415                         send_sig(SIGPIPE, current, 0);
1416                         ret = -EPIPE;
1417                         break;
1418                 }
1419                 if (flags & SPLICE_F_NONBLOCK) {
1420                         ret = -EAGAIN;
1421                         break;
1422                 }
1423                 if (signal_pending(current)) {
1424                         ret = -ERESTARTSYS;
1425                         break;
1426                 }
1427                 pipe_wait_writable(pipe);
1428         }
1429
1430         pipe_unlock(pipe);
1431         return ret;
1432 }
1433
1434 /*
1435  * Splice contents of ipipe to opipe.
1436  */
1437 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1438                                struct pipe_inode_info *opipe,
1439                                size_t len, unsigned int flags)
1440 {
1441         struct pipe_buffer *ibuf, *obuf;
1442         unsigned int i_head, o_head;
1443         unsigned int i_tail, o_tail;
1444         unsigned int i_mask, o_mask;
1445         int ret = 0;
1446         bool input_wakeup = false;
1447
1448
1449 retry:
1450         ret = ipipe_prep(ipipe, flags);
1451         if (ret)
1452                 return ret;
1453
1454         ret = opipe_prep(opipe, flags);
1455         if (ret)
1456                 return ret;
1457
1458         /*
1459          * Potential ABBA deadlock, work around it by ordering lock
1460          * grabbing by pipe info address. Otherwise two different processes
1461          * could deadlock (one doing tee from A -> B, the other from B -> A).
1462          */
1463         pipe_double_lock(ipipe, opipe);
1464
1465         i_tail = ipipe->tail;
1466         i_mask = ipipe->ring_size - 1;
1467         o_head = opipe->head;
1468         o_mask = opipe->ring_size - 1;
1469
1470         do {
1471                 size_t o_len;
1472
1473                 if (!opipe->readers) {
1474                         send_sig(SIGPIPE, current, 0);
1475                         if (!ret)
1476                                 ret = -EPIPE;
1477                         break;
1478                 }
1479
1480                 i_head = ipipe->head;
1481                 o_tail = opipe->tail;
1482
1483                 if (pipe_empty(i_head, i_tail) && !ipipe->writers)
1484                         break;
1485
1486                 /*
1487                  * Cannot make any progress, because either the input
1488                  * pipe is empty or the output pipe is full.
1489                  */
1490                 if (pipe_empty(i_head, i_tail) ||
1491                     pipe_full(o_head, o_tail, opipe->max_usage)) {
1492                         /* Already processed some buffers, break */
1493                         if (ret)
1494                                 break;
1495
1496                         if (flags & SPLICE_F_NONBLOCK) {
1497                                 ret = -EAGAIN;
1498                                 break;
1499                         }
1500
1501                         /*
1502                          * We raced with another reader/writer and haven't
1503                          * managed to process any buffers.  A zero return
1504                          * value means EOF, so retry instead.
1505                          */
1506                         pipe_unlock(ipipe);
1507                         pipe_unlock(opipe);
1508                         goto retry;
1509                 }
1510
1511                 ibuf = &ipipe->bufs[i_tail & i_mask];
1512                 obuf = &opipe->bufs[o_head & o_mask];
1513
1514                 if (len >= ibuf->len) {
1515                         /*
1516                          * Simply move the whole buffer from ipipe to opipe
1517                          */
1518                         *obuf = *ibuf;
1519                         ibuf->ops = NULL;
1520                         i_tail++;
1521                         ipipe->tail = i_tail;
1522                         input_wakeup = true;
1523                         o_len = obuf->len;
1524                         o_head++;
1525                         opipe->head = o_head;
1526                 } else {
1527                         /*
1528                          * Get a reference to this pipe buffer,
1529                          * so we can copy the contents over.
1530                          */
1531                         if (!pipe_buf_get(ipipe, ibuf)) {
1532                                 if (ret == 0)
1533                                         ret = -EFAULT;
1534                                 break;
1535                         }
1536                         *obuf = *ibuf;
1537
1538                         /*
1539                          * Don't inherit the gift and merge flags, we need to
1540                          * prevent multiple steals of this page.
1541                          */
1542                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1543                         obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1544
1545                         obuf->len = len;
1546                         ibuf->offset += len;
1547                         ibuf->len -= len;
1548                         o_len = len;
1549                         o_head++;
1550                         opipe->head = o_head;
1551                 }
1552                 ret += o_len;
1553                 len -= o_len;
1554         } while (len);
1555
1556         pipe_unlock(ipipe);
1557         pipe_unlock(opipe);
1558
1559         /*
1560          * If we put data in the output pipe, wakeup any potential readers.
1561          */
1562         if (ret > 0)
1563                 wakeup_pipe_readers(opipe);
1564
1565         if (input_wakeup)
1566                 wakeup_pipe_writers(ipipe);
1567
1568         return ret;
1569 }
1570
1571 /*
1572  * Link contents of ipipe to opipe.
1573  */
1574 static int link_pipe(struct pipe_inode_info *ipipe,
1575                      struct pipe_inode_info *opipe,
1576                      size_t len, unsigned int flags)
1577 {
1578         struct pipe_buffer *ibuf, *obuf;
1579         unsigned int i_head, o_head;
1580         unsigned int i_tail, o_tail;
1581         unsigned int i_mask, o_mask;
1582         int ret = 0;
1583
1584         /*
1585          * Potential ABBA deadlock, work around it by ordering lock
1586          * grabbing by pipe info address. Otherwise two different processes
1587          * could deadlock (one doing tee from A -> B, the other from B -> A).
1588          */
1589         pipe_double_lock(ipipe, opipe);
1590
1591         i_tail = ipipe->tail;
1592         i_mask = ipipe->ring_size - 1;
1593         o_head = opipe->head;
1594         o_mask = opipe->ring_size - 1;
1595
1596         do {
1597                 if (!opipe->readers) {
1598                         send_sig(SIGPIPE, current, 0);
1599                         if (!ret)
1600                                 ret = -EPIPE;
1601                         break;
1602                 }
1603
1604                 i_head = ipipe->head;
1605                 o_tail = opipe->tail;
1606
1607                 /*
1608                  * If we have iterated all input buffers or run out of
1609                  * output room, break.
1610                  */
1611                 if (pipe_empty(i_head, i_tail) ||
1612                     pipe_full(o_head, o_tail, opipe->max_usage))
1613                         break;
1614
1615                 ibuf = &ipipe->bufs[i_tail & i_mask];
1616                 obuf = &opipe->bufs[o_head & o_mask];
1617
1618                 /*
1619                  * Get a reference to this pipe buffer,
1620                  * so we can copy the contents over.
1621                  */
1622                 if (!pipe_buf_get(ipipe, ibuf)) {
1623                         if (ret == 0)
1624                                 ret = -EFAULT;
1625                         break;
1626                 }
1627
1628                 *obuf = *ibuf;
1629
1630                 /*
1631                  * Don't inherit the gift and merge flag, we need to prevent
1632                  * multiple steals of this page.
1633                  */
1634                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1635                 obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1636
1637                 if (obuf->len > len)
1638                         obuf->len = len;
1639                 ret += obuf->len;
1640                 len -= obuf->len;
1641
1642                 o_head++;
1643                 opipe->head = o_head;
1644                 i_tail++;
1645         } while (len);
1646
1647         pipe_unlock(ipipe);
1648         pipe_unlock(opipe);
1649
1650         /*
1651          * If we put data in the output pipe, wakeup any potential readers.
1652          */
1653         if (ret > 0)
1654                 wakeup_pipe_readers(opipe);
1655
1656         return ret;
1657 }
1658
1659 /*
1660  * This is a tee(1) implementation that works on pipes. It doesn't copy
1661  * any data, it simply references the 'in' pages on the 'out' pipe.
1662  * The 'flags' used are the SPLICE_F_* variants, currently the only
1663  * applicable one is SPLICE_F_NONBLOCK.
1664  */
1665 long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
1666 {
1667         struct pipe_inode_info *ipipe = get_pipe_info(in, true);
1668         struct pipe_inode_info *opipe = get_pipe_info(out, true);
1669         int ret = -EINVAL;
1670
1671         if (unlikely(!(in->f_mode & FMODE_READ) ||
1672                      !(out->f_mode & FMODE_WRITE)))
1673                 return -EBADF;
1674
1675         /*
1676          * Duplicate the contents of ipipe to opipe without actually
1677          * copying the data.
1678          */
1679         if (ipipe && opipe && ipipe != opipe) {
1680                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1681                         flags |= SPLICE_F_NONBLOCK;
1682
1683                 /*
1684                  * Keep going, unless we encounter an error. The ipipe/opipe
1685                  * ordering doesn't really matter.
1686                  */
1687                 ret = ipipe_prep(ipipe, flags);
1688                 if (!ret) {
1689                         ret = opipe_prep(opipe, flags);
1690                         if (!ret)
1691                                 ret = link_pipe(ipipe, opipe, len, flags);
1692                 }
1693         }
1694
1695         return ret;
1696 }
1697
1698 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1699 {
1700         struct fd in, out;
1701         int error;
1702
1703         if (unlikely(flags & ~SPLICE_F_ALL))
1704                 return -EINVAL;
1705
1706         if (unlikely(!len))
1707                 return 0;
1708
1709         error = -EBADF;
1710         in = fdget(fdin);
1711         if (in.file) {
1712                 out = fdget(fdout);
1713                 if (out.file) {
1714                         error = do_tee(in.file, out.file, len, flags);
1715                         fdput(out);
1716                 }
1717                 fdput(in);
1718         }
1719
1720         return error;
1721 }