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 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 true;
  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 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++, n++) {
 666                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 667                         size_t this_len = buf->len;
 668
 669                         if (this_len > left)
 670                                 this_len = left;
 671
 672                         ret = pipe_buf_confirm(pipe, buf);
 673                         if (unlikely(ret)) {
 674                                 if (ret == -ENODATA)
 675                                         ret = 0;
 676                                 goto done;
 677                         }
 678
 679                         array[n].bv_page = buf->page;
 680                         array[n].bv_len = this_len;
 681                         array[n].bv_offset = buf->offset;
 682                         left -= this_len;
 683                 }
 684
 685                 iov_iter_bvec(&from, WRITE, array, n, sd.total_len - left);
 686                 ret = vfs_iter_write(out, &from, &sd.pos, 0);
 687                 if (ret <= 0)
 688                         break;
 689
 690                 sd.num_spliced += ret;
 691                 sd.total_len -= ret;
 692                 *ppos = sd.pos;
 693
 694                 /* dismiss the fully eaten buffers, adjust the partial one */
 695                 tail = pipe->tail;
 696                 while (ret) {
 697                         struct pipe_buffer *buf = &pipe->bufs[tail & mask];
 698                         if (ret >= buf->len) {
 699                                 ret -= buf->len;
 700                                 buf->len = 0;
 701                                 pipe_buf_release(pipe, buf);
 702                                 tail++;
 703                                 pipe->tail = tail;
 704                                 if (pipe->files)
 705                                         sd.need_wakeup = true;
 706                         } else {
 707                                 buf->offset += ret;
 708                                 buf->len -= ret;
 709                                 ret = 0;
 710                         }
 711                 }
 712         }
 713 done:
 714         kfree(array);
 715         splice_from_pipe_end(pipe, &sd);
 716
 717         pipe_unlock(pipe);
 718
 719         if (sd.num_spliced)
 720                 ret = sd.num_spliced;
 721
 722         return ret;
 723 }
 724
 725 EXPORT_SYMBOL(iter_file_splice_write);
 726
 727 /**
 728  * generic_splice_sendpage - splice data from a pipe to a socket
 729  * @pipe:       pipe to splice from
 730  * @out:        socket to write to
 731  * @ppos:       position in @out
 732  * @len:        number of bytes to splice
 733  * @flags:      splice modifier flags
 734  *
 735  * Description:
 736  *    Will send @len bytes from the pipe to a network socket. No data copying
 737  *    is involved.
 738  *
 739  */
 740 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
 741                                 loff_t *ppos, size_t len, unsigned int flags)
 742 {
 743         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 744 }
 745
 746 EXPORT_SYMBOL(generic_splice_sendpage);
 747
 748 static int warn_unsupported(struct file *file, const char *op)
 749 {
 750         pr_debug_ratelimited(
 751                 "splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
 752                 op, file, current->pid, current->comm);
 753         return -EINVAL;
 754 }
 755
 756 /*
 757  * Attempt to initiate a splice from pipe to file.
 758  */
 759 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 760                            loff_t *ppos, size_t len, unsigned int flags)
 761 {
 762         if (unlikely(!out->f_op->splice_write))
 763                 return warn_unsupported(out, "write");
 764         return out->f_op->splice_write(pipe, out, ppos, len, flags);
 765 }
 766
 767 /*
 768  * Attempt to initiate a splice from a file to a pipe.
 769  */
 770 static long do_splice_to(struct file *in, loff_t *ppos,
 771                          struct pipe_inode_info *pipe, size_t len,
 772                          unsigned int flags)
 773 {
 774         int ret;
 775
 776         if (unlikely(!(in->f_mode & FMODE_READ)))
 777                 return -EBADF;
 778
 779         ret = rw_verify_area(READ, in, ppos, len);
 780         if (unlikely(ret < 0))
 781                 return ret;
 782
 783         if (unlikely(len > MAX_RW_COUNT))
 784                 len = MAX_RW_COUNT;
 785
 786         if (unlikely(!in->f_op->splice_read))
 787                 return warn_unsupported(in, "read");
 788         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 789 }
 790
 791 /**
 792  * splice_direct_to_actor - splices data directly between two non-pipes
 793  * @in:         file to splice from
 794  * @sd:         actor information on where to splice to
 795  * @actor:      handles the data splicing
 796  *
 797  * Description:
 798  *    This is a special case helper to splice directly between two
 799  *    points, without requiring an explicit pipe. Internally an allocated
 800  *    pipe is cached in the process, and reused during the lifetime of
 801  *    that process.
 802  *
 803  */
 804 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 805                                splice_direct_actor *actor)
 806 {
 807         struct pipe_inode_info *pipe;
 808         long ret, bytes;
 809         umode_t i_mode;
 810         size_t len;
 811         int i, flags, more;
 812
 813         /*
 814          * We require the input being a regular file, as we don't want to
 815          * randomly drop data for eg socket -> socket splicing. Use the
 816          * piped splicing for that!
 817          */
 818         i_mode = file_inode(in)->i_mode;
 819         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
 820                 return -EINVAL;
 821
 822         /*
 823          * neither in nor out is a pipe, setup an internal pipe attached to
 824          * 'out' and transfer the wanted data from 'in' to 'out' through that
 825          */
 826         pipe = current->splice_pipe;
 827         if (unlikely(!pipe)) {
 828                 pipe = alloc_pipe_info();
 829                 if (!pipe)
 830                         return -ENOMEM;
 831
 832                 /*
 833                  * We don't have an immediate reader, but we'll read the stuff
 834                  * out of the pipe right after the splice_to_pipe(). So set
 835                  * PIPE_READERS appropriately.
 836                  */
 837                 pipe->readers = 1;
 838
 839                 current->splice_pipe = pipe;
 840         }
 841
 842         /*
 843          * Do the splice.
 844          */
 845         ret = 0;
 846         bytes = 0;
 847         len = sd->total_len;
 848         flags = sd->flags;
 849
 850         /*
 851          * Don't block on output, we have to drain the direct pipe.
 852          */
 853         sd->flags &= ~SPLICE_F_NONBLOCK;
 854         more = sd->flags & SPLICE_F_MORE;
 855
 856         WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail));
 857
 858         while (len) {
 859                 unsigned int p_space;
 860                 size_t read_len;
 861                 loff_t pos = sd->pos, prev_pos = pos;
 862
 863                 /* Don't try to read more the pipe has space for. */
 864                 p_space = pipe->max_usage -
 865                         pipe_occupancy(pipe->head, pipe->tail);
 866                 read_len = min_t(size_t, len, p_space << PAGE_SHIFT);
 867                 ret = do_splice_to(in, &pos, pipe, read_len, flags);
 868                 if (unlikely(ret <= 0))
 869                         goto out_release;
 870
 871                 read_len = ret;
 872                 sd->total_len = read_len;
 873
 874                 /*
 875                  * If more data is pending, set SPLICE_F_MORE
 876                  * If this is the last data and SPLICE_F_MORE was not set
 877                  * initially, clears it.
 878                  */
 879                 if (read_len < len)
 880                         sd->flags |= SPLICE_F_MORE;
 881                 else if (!more)
 882                         sd->flags &= ~SPLICE_F_MORE;
 883                 /*
 884                  * NOTE: nonblocking mode only applies to the input. We
 885                  * must not do the output in nonblocking mode as then we
 886                  * could get stuck data in the internal pipe:
 887                  */
 888                 ret = actor(pipe, sd);
 889                 if (unlikely(ret <= 0)) {
 890                         sd->pos = prev_pos;
 891                         goto out_release;
 892                 }
 893
 894                 bytes += ret;
 895                 len -= ret;
 896                 sd->pos = pos;
 897
 898                 if (ret < read_len) {
 899                         sd->pos = prev_pos + ret;
 900                         goto out_release;
 901                 }
 902         }
 903
 904 done:
 905         pipe->tail = pipe->head = 0;
 906         file_accessed(in);
 907         return bytes;
 908
 909 out_release:
 910         /*
 911          * If we did an incomplete transfer we must release
 912          * the pipe buffers in question:
 913          */
 914         for (i = 0; i < pipe->ring_size; i++) {
 915                 struct pipe_buffer *buf = &pipe->bufs[i];
 916
 917                 if (buf->ops)
 918                         pipe_buf_release(pipe, buf);
 919         }
 920
 921         if (!bytes)
 922                 bytes = ret;
 923
 924         goto done;
 925 }
 926 EXPORT_SYMBOL(splice_direct_to_actor);
 927
 928 static int direct_splice_actor(struct pipe_inode_info *pipe,
 929                                struct splice_desc *sd)
 930 {
 931         struct file *file = sd->u.file;
 932
 933         return do_splice_from(pipe, file, sd->opos, sd->total_len,
 934                               sd->flags);
 935 }
 936
 937 /**
 938  * do_splice_direct - splices data directly between two files
 939  * @in:         file to splice from
 940  * @ppos:       input file offset
 941  * @out:        file to splice to
 942  * @opos:       output file offset
 943  * @len:        number of bytes to splice
 944  * @flags:      splice modifier flags
 945  *
 946  * Description:
 947  *    For use by do_sendfile(). splice can easily emulate sendfile, but
 948  *    doing it in the application would incur an extra system call
 949  *    (splice in + splice out, as compared to just sendfile()). So this helper
 950  *    can splice directly through a process-private pipe.
 951  *
 952  */
 953 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 954                       loff_t *opos, size_t len, unsigned int flags)
 955 {
 956         struct splice_desc sd = {
 957                 .len            = len,
 958                 .total_len      = len,
 959                 .flags          = flags,
 960                 .pos            = *ppos,
 961                 .u.file         = out,
 962                 .opos           = opos,
 963         };
 964         long ret;
 965
 966         if (unlikely(!(out->f_mode & FMODE_WRITE)))
 967                 return -EBADF;
 968
 969         if (unlikely(out->f_flags & O_APPEND))
 970                 return -EINVAL;
 971
 972         ret = rw_verify_area(WRITE, out, opos, len);
 973         if (unlikely(ret < 0))
 974                 return ret;
 975
 976         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
 977         if (ret > 0)
 978                 *ppos = sd.pos;
 979
 980         return ret;
 981 }
 982 EXPORT_SYMBOL(do_splice_direct);
 983
 984 static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
 985 {
 986         for (;;) {
 987                 if (unlikely(!pipe->readers)) {
 988                         send_sig(SIGPIPE, current, 0);
 989                         return -EPIPE;
 990                 }
 991                 if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
 992                         return 0;
 993                 if (flags & SPLICE_F_NONBLOCK)
 994                         return -EAGAIN;
 995                 if (signal_pending(current))
 996                         return -ERESTARTSYS;
 997                 pipe_wait_writable(pipe);
 998         }
 999 }
1000
1001 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1002                                struct pipe_inode_info *opipe,
1003                                size_t len, unsigned int flags);
1004
1005 /*
1006  * Determine where to splice to/from.
1007  */
1008 long do_splice(struct file *in, loff_t *off_in, struct file *out,
1009                loff_t *off_out, size_t len, unsigned int flags)
1010 {
1011         struct pipe_inode_info *ipipe;
1012         struct pipe_inode_info *opipe;
1013         loff_t offset;
1014         long ret;
1015
1016         if (unlikely(!(in->f_mode & FMODE_READ) ||
1017                      !(out->f_mode & FMODE_WRITE)))
1018                 return -EBADF;
1019
1020         ipipe = get_pipe_info(in, true);
1021         opipe = get_pipe_info(out, true);
1022
1023         if (ipipe && opipe) {
1024                 if (off_in || off_out)
1025                         return -ESPIPE;
1026
1027                 /* Splicing to self would be fun, but... */
1028                 if (ipipe == opipe)
1029                         return -EINVAL;
1030
1031                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1032                         flags |= SPLICE_F_NONBLOCK;
1033
1034                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1035         }
1036
1037         if (ipipe) {
1038                 if (off_in)
1039                         return -ESPIPE;
1040                 if (off_out) {
1041                         if (!(out->f_mode & FMODE_PWRITE))
1042                                 return -EINVAL;
1043                         offset = *off_out;
1044                 } else {
1045                         offset = out->f_pos;
1046                 }
1047
1048                 if (unlikely(out->f_flags & O_APPEND))
1049                         return -EINVAL;
1050
1051                 ret = rw_verify_area(WRITE, out, &offset, len);
1052                 if (unlikely(ret < 0))
1053                         return ret;
1054
1055                 if (in->f_flags & O_NONBLOCK)
1056                         flags |= SPLICE_F_NONBLOCK;
1057
1058                 file_start_write(out);
1059                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1060                 file_end_write(out);
1061
1062                 if (!off_out)
1063                         out->f_pos = offset;
1064                 else
1065                         *off_out = offset;
1066
1067                 return ret;
1068         }
1069
1070         if (opipe) {
1071                 if (off_out)
1072                         return -ESPIPE;
1073                 if (off_in) {
1074                         if (!(in->f_mode & FMODE_PREAD))
1075                                 return -EINVAL;
1076                         offset = *off_in;
1077                 } else {
1078                         offset = in->f_pos;
1079                 }
1080
1081                 if (out->f_flags & O_NONBLOCK)
1082                         flags |= SPLICE_F_NONBLOCK;
1083
1084                 pipe_lock(opipe);
1085                 ret = wait_for_space(opipe, flags);
1086                 if (!ret) {
1087                         unsigned int p_space;
1088
1089                         /* Don't try to read more the pipe has space for. */
1090                         p_space = opipe->max_usage - pipe_occupancy(opipe->head, opipe->tail);
1091                         len = min_t(size_t, len, p_space << PAGE_SHIFT);
1092
1093                         ret = do_splice_to(in, &offset, opipe, len, flags);
1094                 }
1095                 pipe_unlock(opipe);
1096                 if (ret > 0)
1097                         wakeup_pipe_readers(opipe);
1098                 if (!off_in)
1099                         in->f_pos = offset;
1100                 else
1101                         *off_in = offset;
1102
1103                 return ret;
1104         }
1105
1106         return -EINVAL;
1107 }
1108
1109 static long __do_splice(struct file *in, loff_t __user *off_in,
1110                         struct file *out, loff_t __user *off_out,
1111                         size_t len, unsigned int flags)
1112 {
1113         struct pipe_inode_info *ipipe;
1114         struct pipe_inode_info *opipe;
1115         loff_t offset, *__off_in = NULL, *__off_out = NULL;
1116         long ret;
1117
1118         ipipe = get_pipe_info(in, true);
1119         opipe = get_pipe_info(out, true);
1120
1121         if (ipipe && off_in)
1122                 return -ESPIPE;
1123         if (opipe && off_out)
1124                 return -ESPIPE;
1125
1126         if (off_out) {
1127                 if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1128                         return -EFAULT;
1129                 __off_out = &offset;
1130         }
1131         if (off_in) {
1132                 if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1133                         return -EFAULT;
1134                 __off_in = &offset;
1135         }
1136
1137         ret = do_splice(in, __off_in, out, __off_out, len, flags);
1138         if (ret < 0)
1139                 return ret;
1140
1141         if (__off_out && copy_to_user(off_out, __off_out, sizeof(loff_t)))
1142                 return -EFAULT;
1143         if (__off_in && copy_to_user(off_in, __off_in, sizeof(loff_t)))
1144                 return -EFAULT;
1145
1146         return ret;
1147 }
1148
1149 static int iter_to_pipe(struct iov_iter *from,
1150                         struct pipe_inode_info *pipe,
1151                         unsigned flags)
1152 {
1153         struct pipe_buffer buf = {
1154                 .ops = &user_page_pipe_buf_ops,
1155                 .flags = flags
1156         };
1157         size_t total = 0;
1158         int ret = 0;
1159         bool failed = false;
1160
1161         while (iov_iter_count(from) && !failed) {
1162                 struct page *pages[16];
1163                 ssize_t copied;
1164                 size_t start;
1165                 int n;
1166
1167                 copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
1168                 if (copied <= 0) {
1169                         ret = copied;
1170                         break;
1171                 }
1172
1173                 for (n = 0; copied; n++, start = 0) {
1174                         int size = min_t(int, copied, PAGE_SIZE - start);
1175                         if (!failed) {
1176                                 buf.page = pages[n];
1177                                 buf.offset = start;
1178                                 buf.len = size;
1179                                 ret = add_to_pipe(pipe, &buf);
1180                                 if (unlikely(ret < 0)) {
1181                                         failed = true;
1182                                 } else {
1183                                         iov_iter_advance(from, ret);
1184                                         total += ret;
1185                                 }
1186                         } else {
1187                                 put_page(pages[n]);
1188                         }
1189                         copied -= size;
1190                 }
1191         }
1192         return total ? total : ret;
1193 }
1194
1195 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1196                         struct splice_desc *sd)
1197 {
1198         int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
1199         return n == sd->len ? n : -EFAULT;
1200 }
1201
1202 /*
1203  * For lack of a better implementation, implement vmsplice() to userspace
1204  * as a simple copy of the pipes pages to the user iov.
1205  */
1206 static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
1207                              unsigned int flags)
1208 {
1209         struct pipe_inode_info *pipe = get_pipe_info(file, true);
1210         struct splice_desc sd = {
1211                 .total_len = iov_iter_count(iter),
1212                 .flags = flags,
1213                 .u.data = iter
1214         };
1215         long ret = 0;
1216
1217         if (!pipe)
1218                 return -EBADF;
1219
1220         if (sd.total_len) {
1221                 pipe_lock(pipe);
1222                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
1223                 pipe_unlock(pipe);
1224         }
1225
1226         return ret;
1227 }
1228
1229 /*
1230  * vmsplice splices a user address range into a pipe. It can be thought of
1231  * as splice-from-memory, where the regular splice is splice-from-file (or
1232  * to file). In both cases the output is a pipe, naturally.
1233  */
1234 static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
1235                              unsigned int flags)
1236 {
1237         struct pipe_inode_info *pipe;
1238         long ret = 0;
1239         unsigned buf_flag = 0;
1240
1241         if (flags & SPLICE_F_GIFT)
1242                 buf_flag = PIPE_BUF_FLAG_GIFT;
1243
1244         pipe = get_pipe_info(file, true);
1245         if (!pipe)
1246                 return -EBADF;
1247
1248         pipe_lock(pipe);
1249         ret = wait_for_space(pipe, flags);
1250         if (!ret)
1251                 ret = iter_to_pipe(iter, pipe, buf_flag);
1252         pipe_unlock(pipe);
1253         if (ret > 0)
1254                 wakeup_pipe_readers(pipe);
1255         return ret;
1256 }
1257
1258 static int vmsplice_type(struct fd f, int *type)
1259 {
1260         if (!f.file)
1261                 return -EBADF;
1262         if (f.file->f_mode & FMODE_WRITE) {
1263                 *type = WRITE;
1264         } else if (f.file->f_mode & FMODE_READ) {
1265                 *type = READ;
1266         } else {
1267                 fdput(f);
1268                 return -EBADF;
1269         }
1270         return 0;
1271 }
1272
1273 /*
1274  * Note that vmsplice only really supports true splicing _from_ user memory
1275  * to a pipe, not the other way around. Splicing from user memory is a simple
1276  * operation that can be supported without any funky alignment restrictions
1277  * or nasty vm tricks. We simply map in the user memory and fill them into
1278  * a pipe. The reverse isn't quite as easy, though. There are two possible
1279  * solutions for that:
1280  *
1281  *      - memcpy() the data internally, at which point we might as well just
1282  *        do a regular read() on the buffer anyway.
1283  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1284  *        has restriction limitations on both ends of the pipe).
1285  *
1286  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1287  *
1288  */
1289 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
1290                 unsigned long, nr_segs, unsigned int, flags)
1291 {
1292         struct iovec iovstack[UIO_FASTIOV];
1293         struct iovec *iov = iovstack;
1294         struct iov_iter iter;
1295         ssize_t error;
1296         struct fd f;
1297         int type;
1298
1299         if (unlikely(flags & ~SPLICE_F_ALL))
1300                 return -EINVAL;
1301
1302         f = fdget(fd);
1303         error = vmsplice_type(f, &type);
1304         if (error)
1305                 return error;
1306
1307         error = import_iovec(type, uiov, nr_segs,
1308                              ARRAY_SIZE(iovstack), &iov, &iter);
1309         if (error < 0)
1310                 goto out_fdput;
1311
1312         if (!iov_iter_count(&iter))
1313                 error = 0;
1314         else if (iov_iter_rw(&iter) == WRITE)
1315                 error = vmsplice_to_pipe(f.file, &iter, flags);
1316         else
1317                 error = vmsplice_to_user(f.file, &iter, flags);
1318
1319         kfree(iov);
1320 out_fdput:
1321         fdput(f);
1322         return error;
1323 }
1324
1325 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1326                 int, fd_out, loff_t __user *, off_out,
1327                 size_t, len, unsigned int, flags)
1328 {
1329         struct fd in, out;
1330         long error;
1331
1332         if (unlikely(!len))
1333                 return 0;
1334
1335         if (unlikely(flags & ~SPLICE_F_ALL))
1336                 return -EINVAL;
1337
1338         error = -EBADF;
1339         in = fdget(fd_in);
1340         if (in.file) {
1341                 out = fdget(fd_out);
1342                 if (out.file) {
1343                         error = __do_splice(in.file, off_in, out.file, off_out,
1344                                                 len, flags);
1345                         fdput(out);
1346                 }
1347                 fdput(in);
1348         }
1349         return error;
1350 }
1351
1352 /*
1353  * Make sure there's data to read. Wait for input if we can, otherwise
1354  * return an appropriate error.
1355  */
1356 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1357 {
1358         int ret;
1359
1360         /*
1361          * Check the pipe occupancy without the inode lock first. This function
1362          * is speculative anyways, so missing one is ok.
1363          */
1364         if (!pipe_empty(pipe->head, pipe->tail))
1365                 return 0;
1366
1367         ret = 0;
1368         pipe_lock(pipe);
1369
1370         while (pipe_empty(pipe->head, pipe->tail)) {
1371                 if (signal_pending(current)) {
1372                         ret = -ERESTARTSYS;
1373                         break;
1374                 }
1375                 if (!pipe->writers)
1376                         break;
1377                 if (flags & SPLICE_F_NONBLOCK) {
1378                         ret = -EAGAIN;
1379                         break;
1380                 }
1381                 pipe_wait_readable(pipe);
1382         }
1383
1384         pipe_unlock(pipe);
1385         return ret;
1386 }
1387
1388 /*
1389  * Make sure there's writeable room. Wait for room if we can, otherwise
1390  * return an appropriate error.
1391  */
1392 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1393 {
1394         int ret;
1395
1396         /*
1397          * Check pipe occupancy without the inode lock first. This function
1398          * is speculative anyways, so missing one is ok.
1399          */
1400         if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage))
1401                 return 0;
1402
1403         ret = 0;
1404         pipe_lock(pipe);
1405
1406         while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
1407                 if (!pipe->readers) {
1408                         send_sig(SIGPIPE, current, 0);
1409                         ret = -EPIPE;
1410                         break;
1411                 }
1412                 if (flags & SPLICE_F_NONBLOCK) {
1413                         ret = -EAGAIN;
1414                         break;
1415                 }
1416                 if (signal_pending(current)) {
1417                         ret = -ERESTARTSYS;
1418                         break;
1419                 }
1420                 pipe_wait_writable(pipe);
1421         }
1422
1423         pipe_unlock(pipe);
1424         return ret;
1425 }
1426
1427 /*
1428  * Splice contents of ipipe to opipe.
1429  */
1430 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1431                                struct pipe_inode_info *opipe,
1432                                size_t len, unsigned int flags)
1433 {
1434         struct pipe_buffer *ibuf, *obuf;
1435         unsigned int i_head, o_head;
1436         unsigned int i_tail, o_tail;
1437         unsigned int i_mask, o_mask;
1438         int ret = 0;
1439         bool input_wakeup = false;
1440
1441
1442 retry:
1443         ret = ipipe_prep(ipipe, flags);
1444         if (ret)
1445                 return ret;
1446
1447         ret = opipe_prep(opipe, flags);
1448         if (ret)
1449                 return ret;
1450
1451         /*
1452          * Potential ABBA deadlock, work around it by ordering lock
1453          * grabbing by pipe info address. Otherwise two different processes
1454          * could deadlock (one doing tee from A -> B, the other from B -> A).
1455          */
1456         pipe_double_lock(ipipe, opipe);
1457
1458         i_tail = ipipe->tail;
1459         i_mask = ipipe->ring_size - 1;
1460         o_head = opipe->head;
1461         o_mask = opipe->ring_size - 1;
1462
1463         do {
1464                 size_t o_len;
1465
1466                 if (!opipe->readers) {
1467                         send_sig(SIGPIPE, current, 0);
1468                         if (!ret)
1469                                 ret = -EPIPE;
1470                         break;
1471                 }
1472
1473                 i_head = ipipe->head;
1474                 o_tail = opipe->tail;
1475
1476                 if (pipe_empty(i_head, i_tail) && !ipipe->writers)
1477                         break;
1478
1479                 /*
1480                  * Cannot make any progress, because either the input
1481                  * pipe is empty or the output pipe is full.
1482                  */
1483                 if (pipe_empty(i_head, i_tail) ||
1484                     pipe_full(o_head, o_tail, opipe->max_usage)) {
1485                         /* Already processed some buffers, break */
1486                         if (ret)
1487                                 break;
1488
1489                         if (flags & SPLICE_F_NONBLOCK) {
1490                                 ret = -EAGAIN;
1491                                 break;
1492                         }
1493
1494                         /*
1495                          * We raced with another reader/writer and haven't
1496                          * managed to process any buffers.  A zero return
1497                          * value means EOF, so retry instead.
1498                          */
1499                         pipe_unlock(ipipe);
1500                         pipe_unlock(opipe);
1501                         goto retry;
1502                 }
1503
1504                 ibuf = &ipipe->bufs[i_tail & i_mask];
1505                 obuf = &opipe->bufs[o_head & o_mask];
1506
1507                 if (len >= ibuf->len) {
1508                         /*
1509                          * Simply move the whole buffer from ipipe to opipe
1510                          */
1511                         *obuf = *ibuf;
1512                         ibuf->ops = NULL;
1513                         i_tail++;
1514                         ipipe->tail = i_tail;
1515                         input_wakeup = true;
1516                         o_len = obuf->len;
1517                         o_head++;
1518                         opipe->head = o_head;
1519                 } else {
1520                         /*
1521                          * Get a reference to this pipe buffer,
1522                          * so we can copy the contents over.
1523                          */
1524                         if (!pipe_buf_get(ipipe, ibuf)) {
1525                                 if (ret == 0)
1526                                         ret = -EFAULT;
1527                                 break;
1528                         }
1529                         *obuf = *ibuf;
1530
1531                         /*
1532                          * Don't inherit the gift and merge flags, we need to
1533                          * prevent multiple steals of this page.
1534                          */
1535                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1536                         obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1537
1538                         obuf->len = len;
1539                         ibuf->offset += len;
1540                         ibuf->len -= len;
1541                         o_len = len;
1542                         o_head++;
1543                         opipe->head = o_head;
1544                 }
1545                 ret += o_len;
1546                 len -= o_len;
1547         } while (len);
1548
1549         pipe_unlock(ipipe);
1550         pipe_unlock(opipe);
1551
1552         /*
1553          * If we put data in the output pipe, wakeup any potential readers.
1554          */
1555         if (ret > 0)
1556                 wakeup_pipe_readers(opipe);
1557
1558         if (input_wakeup)
1559                 wakeup_pipe_writers(ipipe);
1560
1561         return ret;
1562 }
1563
1564 /*
1565  * Link contents of ipipe to opipe.
1566  */
1567 static int link_pipe(struct pipe_inode_info *ipipe,
1568                      struct pipe_inode_info *opipe,
1569                      size_t len, unsigned int flags)
1570 {
1571         struct pipe_buffer *ibuf, *obuf;
1572         unsigned int i_head, o_head;
1573         unsigned int i_tail, o_tail;
1574         unsigned int i_mask, o_mask;
1575         int ret = 0;
1576
1577         /*
1578          * Potential ABBA deadlock, work around it by ordering lock
1579          * grabbing by pipe info address. Otherwise two different processes
1580          * could deadlock (one doing tee from A -> B, the other from B -> A).
1581          */
1582         pipe_double_lock(ipipe, opipe);
1583
1584         i_tail = ipipe->tail;
1585         i_mask = ipipe->ring_size - 1;
1586         o_head = opipe->head;
1587         o_mask = opipe->ring_size - 1;
1588
1589         do {
1590                 if (!opipe->readers) {
1591                         send_sig(SIGPIPE, current, 0);
1592                         if (!ret)
1593                                 ret = -EPIPE;
1594                         break;
1595                 }
1596
1597                 i_head = ipipe->head;
1598                 o_tail = opipe->tail;
1599
1600                 /*
1601                  * If we have iterated all input buffers or run out of
1602                  * output room, break.
1603                  */
1604                 if (pipe_empty(i_head, i_tail) ||
1605                     pipe_full(o_head, o_tail, opipe->max_usage))
1606                         break;
1607
1608                 ibuf = &ipipe->bufs[i_tail & i_mask];
1609                 obuf = &opipe->bufs[o_head & o_mask];
1610
1611                 /*
1612                  * Get a reference to this pipe buffer,
1613                  * so we can copy the contents over.
1614                  */
1615                 if (!pipe_buf_get(ipipe, ibuf)) {
1616                         if (ret == 0)
1617                                 ret = -EFAULT;
1618                         break;
1619                 }
1620
1621                 *obuf = *ibuf;
1622
1623                 /*
1624                  * Don't inherit the gift and merge flag, we need to prevent
1625                  * multiple steals of this page.
1626                  */
1627                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1628                 obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
1629
1630                 if (obuf->len > len)
1631                         obuf->len = len;
1632                 ret += obuf->len;
1633                 len -= obuf->len;
1634
1635                 o_head++;
1636                 opipe->head = o_head;
1637                 i_tail++;
1638         } while (len);
1639
1640         pipe_unlock(ipipe);
1641         pipe_unlock(opipe);
1642
1643         /*
1644          * If we put data in the output pipe, wakeup any potential readers.
1645          */
1646         if (ret > 0)
1647                 wakeup_pipe_readers(opipe);
1648
1649         return ret;
1650 }
1651
1652 /*
1653  * This is a tee(1) implementation that works on pipes. It doesn't copy
1654  * any data, it simply references the 'in' pages on the 'out' pipe.
1655  * The 'flags' used are the SPLICE_F_* variants, currently the only
1656  * applicable one is SPLICE_F_NONBLOCK.
1657  */
1658 long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
1659 {
1660         struct pipe_inode_info *ipipe = get_pipe_info(in, true);
1661         struct pipe_inode_info *opipe = get_pipe_info(out, true);
1662         int ret = -EINVAL;
1663
1664         if (unlikely(!(in->f_mode & FMODE_READ) ||
1665                      !(out->f_mode & FMODE_WRITE)))
1666                 return -EBADF;
1667
1668         /*
1669          * Duplicate the contents of ipipe to opipe without actually
1670          * copying the data.
1671          */
1672         if (ipipe && opipe && ipipe != opipe) {
1673                 if ((in->f_flags | out->f_flags) & O_NONBLOCK)
1674                         flags |= SPLICE_F_NONBLOCK;
1675
1676                 /*
1677                  * Keep going, unless we encounter an error. The ipipe/opipe
1678                  * ordering doesn't really matter.
1679                  */
1680                 ret = ipipe_prep(ipipe, flags);
1681                 if (!ret) {
1682                         ret = opipe_prep(opipe, flags);
1683                         if (!ret)
1684                                 ret = link_pipe(ipipe, opipe, len, flags);
1685                 }
1686         }
1687
1688         return ret;
1689 }
1690
1691 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
1692 {
1693         struct fd in, out;
1694         int error;
1695
1696         if (unlikely(flags & ~SPLICE_F_ALL))
1697                 return -EINVAL;
1698
1699         if (unlikely(!len))
1700                 return 0;
1701
1702         error = -EBADF;
1703         in = fdget(fdin);
1704         if (in.file) {
1705                 out = fdget(fdout);
1706                 if (out.file) {
1707                         error = do_tee(in.file, out.file, len, flags);
1708                         fdput(out);
1709                 }
1710                 fdput(in);
1711         }
1712
1713         return error;
1714 }