fs/splice.c

   1 /*
   2  * "splice": joining two ropes together by interweaving their strands.
   3  *
   4  * This is the "extended pipe" functionality, where a pipe is used as
   5  * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6  * buffer that you can use to transfer data from one end to the other.
   7  *
   8  * The traditional unix read/write is extended with a "splice()" operation
   9  * that transfers data buffers to or from a pipe buffer.
  10  *
  11  * Named by Larry McVoy, original implementation from Linus, extended by
  12  * Jens to support splicing to files, network, direct splicing, etc and
  13  * fixing lots of bugs.
  14  *
  15  * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  16  * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  17  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  18  *
  19  */
  20 #include <linux/fs.h>
  21 #include <linux/file.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/splice.h>
  24 #include <linux/memcontrol.h>
  25 #include <linux/mm_inline.h>
  26 #include <linux/swap.h>
  27 #include <linux/writeback.h>
  28 #include <linux/export.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/uio.h>
  31 #include <linux/security.h>
  32 #include <linux/gfp.h>
  33 #include <linux/socket.h>
  34 #include <linux/compat.h>
  35 #include "internal.h"
  36
  37 /*
  38  * Attempt to steal a page from a pipe buffer. This should perhaps go into
  39  * a vm helper function, it's already simplified quite a bit by the
  40  * addition of remove_mapping(). If success is returned, the caller may
  41  * attempt to reuse this page for another destination.
  42  */
  43 static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  44                                      struct pipe_buffer *buf)
  45 {
  46         struct page *page = buf->page;
  47         struct address_space *mapping;
  48
  49         lock_page(page);
  50
  51         mapping = page_mapping(page);
  52         if (mapping) {
  53                 WARN_ON(!PageUptodate(page));
  54
  55                 /*
  56                  * At least for ext2 with nobh option, we need to wait on
  57                  * writeback completing on this page, since we'll remove it
  58                  * from the pagecache.  Otherwise truncate wont wait on the
  59                  * page, allowing the disk blocks to be reused by someone else
  60                  * before we actually wrote our data to them. fs corruption
  61                  * ensues.
  62                  */
  63                 wait_on_page_writeback(page);
  64
  65                 if (page_has_private(page) &&
  66                     !try_to_release_page(page, GFP_KERNEL))
  67                         goto out_unlock;
  68
  69                 /*
  70                  * If we succeeded in removing the mapping, set LRU flag
  71                  * and return good.
  72                  */
  73                 if (remove_mapping(mapping, page)) {
  74                         buf->flags |= PIPE_BUF_FLAG_LRU;
  75                         return 0;
  76                 }
  77         }
  78
  79         /*
  80          * Raced with truncate or failed to remove page from current
  81          * address space, unlock and return failure.
  82          */
  83 out_unlock:
  84         unlock_page(page);
  85         return 1;
  86 }
  87
  88 static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  89                                         struct pipe_buffer *buf)
  90 {
  91         page_cache_release(buf->page);
  92         buf->flags &= ~PIPE_BUF_FLAG_LRU;
  93 }
  94
  95 /*
  96  * Check whether the contents of buf is OK to access. Since the content
  97  * is a page cache page, IO may be in flight.
  98  */
  99 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
 100                                        struct pipe_buffer *buf)
 101 {
 102         struct page *page = buf->page;
 103         int err;
 104
 105         if (!PageUptodate(page)) {
 106                 lock_page(page);
 107
 108                 /*
 109                  * Page got truncated/unhashed. This will cause a 0-byte
 110                  * splice, if this is the first page.
 111                  */
 112                 if (!page->mapping) {
 113                         err = -ENODATA;
 114                         goto error;
 115                 }
 116
 117                 /*
 118                  * Uh oh, read-error from disk.
 119                  */
 120                 if (!PageUptodate(page)) {
 121                         err = -EIO;
 122                         goto error;
 123                 }
 124
 125                 /*
 126                  * Page is ok afterall, we are done.
 127                  */
 128                 unlock_page(page);
 129         }
 130
 131         return 0;
 132 error:
 133         unlock_page(page);
 134         return err;
 135 }
 136
 137 const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 138         .can_merge = 0,
 139         .map = generic_pipe_buf_map,
 140         .unmap = generic_pipe_buf_unmap,
 141         .confirm = page_cache_pipe_buf_confirm,
 142         .release = page_cache_pipe_buf_release,
 143         .steal = page_cache_pipe_buf_steal,
 144         .get = generic_pipe_buf_get,
 145 };
 146
 147 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 148                                     struct pipe_buffer *buf)
 149 {
 150         if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 151                 return 1;
 152
 153         buf->flags |= PIPE_BUF_FLAG_LRU;
 154         return generic_pipe_buf_steal(pipe, buf);
 155 }
 156
 157 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 158         .can_merge = 0,
 159         .map = generic_pipe_buf_map,
 160         .unmap = generic_pipe_buf_unmap,
 161         .confirm = generic_pipe_buf_confirm,
 162         .release = page_cache_pipe_buf_release,
 163         .steal = user_page_pipe_buf_steal,
 164         .get = generic_pipe_buf_get,
 165 };
 166
 167 static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 168 {
 169         smp_mb();
 170         if (waitqueue_active(&pipe->wait))
 171                 wake_up_interruptible(&pipe->wait);
 172         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 173 }
 174
 175 /**
 176  * splice_to_pipe - fill passed data into a pipe
 177  * @pipe:       pipe to fill
 178  * @spd:        data to fill
 179  *
 180  * Description:
 181  *    @spd contains a map of pages and len/offset tuples, along with
 182  *    the struct pipe_buf_operations associated with these pages. This
 183  *    function will link that data to the pipe.
 184  *
 185  */
 186 ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 187                        struct splice_pipe_desc *spd)
 188 {
 189         unsigned int spd_pages = spd->nr_pages;
 190         int ret, do_wakeup, page_nr;
 191
 192         ret = 0;
 193         do_wakeup = 0;
 194         page_nr = 0;
 195
 196         pipe_lock(pipe);
 197
 198         for (;;) {
 199                 if (!pipe->readers) {
 200                         send_sig(SIGPIPE, current, 0);
 201                         if (!ret)
 202                                 ret = -EPIPE;
 203                         break;
 204                 }
 205
 206                 if (pipe->nrbufs < pipe->buffers) {
 207                         int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 208                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 209
 210                         buf->page = spd->pages[page_nr];
 211                         buf->offset = spd->partial[page_nr].offset;
 212                         buf->len = spd->partial[page_nr].len;
 213                         buf->private = spd->partial[page_nr].private;
 214                         buf->ops = spd->ops;
 215                         if (spd->flags & SPLICE_F_GIFT)
 216                                 buf->flags |= PIPE_BUF_FLAG_GIFT;
 217
 218                         pipe->nrbufs++;
 219                         page_nr++;
 220                         ret += buf->len;
 221
 222                         if (pipe->files)
 223                                 do_wakeup = 1;
 224
 225                         if (!--spd->nr_pages)
 226                                 break;
 227                         if (pipe->nrbufs < pipe->buffers)
 228                                 continue;
 229
 230                         break;
 231                 }
 232
 233                 if (spd->flags & SPLICE_F_NONBLOCK) {
 234                         if (!ret)
 235                                 ret = -EAGAIN;
 236                         break;
 237                 }
 238
 239                 if (signal_pending(current)) {
 240                         if (!ret)
 241                                 ret = -ERESTARTSYS;
 242                         break;
 243                 }
 244
 245                 if (do_wakeup) {
 246                         smp_mb();
 247                         if (waitqueue_active(&pipe->wait))
 248                                 wake_up_interruptible_sync(&pipe->wait);
 249                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 250                         do_wakeup = 0;
 251                 }
 252
 253                 pipe->waiting_writers++;
 254                 pipe_wait(pipe);
 255                 pipe->waiting_writers--;
 256         }
 257
 258         pipe_unlock(pipe);
 259
 260         if (do_wakeup)
 261                 wakeup_pipe_readers(pipe);
 262
 263         while (page_nr < spd_pages)
 264                 spd->spd_release(spd, page_nr++);
 265
 266         return ret;
 267 }
 268
 269 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 270 {
 271         page_cache_release(spd->pages[i]);
 272 }
 273
 274 /*
 275  * Check if we need to grow the arrays holding pages and partial page
 276  * descriptions.
 277  */
 278 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 279 {
 280         unsigned int buffers = ACCESS_ONCE(pipe->buffers);
 281
 282         spd->nr_pages_max = buffers;
 283         if (buffers <= PIPE_DEF_BUFFERS)
 284                 return 0;
 285
 286         spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
 287         spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
 288
 289         if (spd->pages && spd->partial)
 290                 return 0;
 291
 292         kfree(spd->pages);
 293         kfree(spd->partial);
 294         return -ENOMEM;
 295 }
 296
 297 void splice_shrink_spd(struct splice_pipe_desc *spd)
 298 {
 299         if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
 300                 return;
 301
 302         kfree(spd->pages);
 303         kfree(spd->partial);
 304 }
 305
 306 static int
 307 __generic_file_splice_read(struct file *in, loff_t *ppos,
 308                            struct pipe_inode_info *pipe, size_t len,
 309                            unsigned int flags)
 310 {
 311         struct address_space *mapping = in->f_mapping;
 312         unsigned int loff, nr_pages, req_pages;
 313         struct page *pages[PIPE_DEF_BUFFERS];
 314         struct partial_page partial[PIPE_DEF_BUFFERS];
 315         struct page *page;
 316         pgoff_t index, end_index;
 317         loff_t isize;
 318         int error, page_nr;
 319         struct splice_pipe_desc spd = {
 320                 .pages = pages,
 321                 .partial = partial,
 322                 .nr_pages_max = PIPE_DEF_BUFFERS,
 323                 .flags = flags,
 324                 .ops = &page_cache_pipe_buf_ops,
 325                 .spd_release = spd_release_page,
 326         };
 327
 328         if (splice_grow_spd(pipe, &spd))
 329                 return -ENOMEM;
 330
 331         index = *ppos >> PAGE_CACHE_SHIFT;
 332         loff = *ppos & ~PAGE_CACHE_MASK;
 333         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 334         nr_pages = min(req_pages, spd.nr_pages_max);
 335
 336         /*
 337          * Lookup the (hopefully) full range of pages we need.
 338          */
 339         spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
 340         index += spd.nr_pages;
 341
 342         /*
 343          * If find_get_pages_contig() returned fewer pages than we needed,
 344          * readahead/allocate the rest and fill in the holes.
 345          */
 346         if (spd.nr_pages < nr_pages)
 347                 page_cache_sync_readahead(mapping, &in->f_ra, in,
 348                                 index, req_pages - spd.nr_pages);
 349
 350         error = 0;
 351         while (spd.nr_pages < nr_pages) {
 352                 /*
 353                  * Page could be there, find_get_pages_contig() breaks on
 354                  * the first hole.
 355                  */
 356                 page = find_get_page(mapping, index);
 357                 if (!page) {
 358                         /*
 359                          * page didn't exist, allocate one.
 360                          */
 361                         page = page_cache_alloc_cold(mapping);
 362                         if (!page)
 363                                 break;
 364
 365                         error = add_to_page_cache_lru(page, mapping, index,
 366                                                 GFP_KERNEL);
 367                         if (unlikely(error)) {
 368                                 page_cache_release(page);
 369                                 if (error == -EEXIST)
 370                                         continue;
 371                                 break;
 372                         }
 373                         /*
 374                          * add_to_page_cache() locks the page, unlock it
 375                          * to avoid convoluting the logic below even more.
 376                          */
 377                         unlock_page(page);
 378                 }
 379
 380                 spd.pages[spd.nr_pages++] = page;
 381                 index++;
 382         }
 383
 384         /*
 385          * Now loop over the map and see if we need to start IO on any
 386          * pages, fill in the partial map, etc.
 387          */
 388         index = *ppos >> PAGE_CACHE_SHIFT;
 389         nr_pages = spd.nr_pages;
 390         spd.nr_pages = 0;
 391         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 392                 unsigned int this_len;
 393
 394                 if (!len)
 395                         break;
 396
 397                 /*
 398                  * this_len is the max we'll use from this page
 399                  */
 400                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 401                 page = spd.pages[page_nr];
 402
 403                 if (PageReadahead(page))
 404                         page_cache_async_readahead(mapping, &in->f_ra, in,
 405                                         page, index, req_pages - page_nr);
 406
 407                 /*
 408                  * If the page isn't uptodate, we may need to start io on it
 409                  */
 410                 if (!PageUptodate(page)) {
 411                         lock_page(page);
 412
 413                         /*
 414                          * Page was truncated, or invalidated by the
 415                          * filesystem.  Redo the find/create, but this time the
 416                          * page is kept locked, so there's no chance of another
 417                          * race with truncate/invalidate.
 418                          */
 419                         if (!page->mapping) {
 420                                 unlock_page(page);
 421                                 page = find_or_create_page(mapping, index,
 422                                                 mapping_gfp_mask(mapping));
 423
 424                                 if (!page) {
 425                                         error = -ENOMEM;
 426                                         break;
 427                                 }
 428                                 page_cache_release(spd.pages[page_nr]);
 429                                 spd.pages[page_nr] = page;
 430                         }
 431                         /*
 432                          * page was already under io and is now done, great
 433                          */
 434                         if (PageUptodate(page)) {
 435                                 unlock_page(page);
 436                                 goto fill_it;
 437                         }
 438
 439                         /*
 440                          * need to read in the page
 441                          */
 442                         error = mapping->a_ops->readpage(in, page);
 443                         if (unlikely(error)) {
 444                                 /*
 445                                  * We really should re-lookup the page here,
 446                                  * but it complicates things a lot. Instead
 447                                  * lets just do what we already stored, and
 448                                  * we'll get it the next time we are called.
 449                                  */
 450                                 if (error == AOP_TRUNCATED_PAGE)
 451                                         error = 0;
 452
 453                                 break;
 454                         }
 455                 }
 456 fill_it:
 457                 /*
 458                  * i_size must be checked after PageUptodate.
 459                  */
 460                 isize = i_size_read(mapping->host);
 461                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 462                 if (unlikely(!isize || index > end_index))
 463                         break;
 464
 465                 /*
 466                  * if this is the last page, see if we need to shrink
 467                  * the length and stop
 468                  */
 469                 if (end_index == index) {
 470                         unsigned int plen;
 471
 472                         /*
 473                          * max good bytes in this page
 474                          */
 475                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 476                         if (plen <= loff)
 477                                 break;
 478
 479                         /*
 480                          * force quit after adding this page
 481                          */
 482                         this_len = min(this_len, plen - loff);
 483                         len = this_len;
 484                 }
 485
 486                 spd.partial[page_nr].offset = loff;
 487                 spd.partial[page_nr].len = this_len;
 488                 len -= this_len;
 489                 loff = 0;
 490                 spd.nr_pages++;
 491                 index++;
 492         }
 493
 494         /*
 495          * Release any pages at the end, if we quit early. 'page_nr' is how far
 496          * we got, 'nr_pages' is how many pages are in the map.
 497          */
 498         while (page_nr < nr_pages)
 499                 page_cache_release(spd.pages[page_nr++]);
 500         in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 501
 502         if (spd.nr_pages)
 503                 error = splice_to_pipe(pipe, &spd);
 504
 505         splice_shrink_spd(&spd);
 506         return error;
 507 }
 508
 509 /**
 510  * generic_file_splice_read - splice data from file to a pipe
 511  * @in:         file to splice from
 512  * @ppos:       position in @in
 513  * @pipe:       pipe to splice to
 514  * @len:        number of bytes to splice
 515  * @flags:      splice modifier flags
 516  *
 517  * Description:
 518  *    Will read pages from given file and fill them into a pipe. Can be
 519  *    used as long as the address_space operations for the source implements
 520  *    a readpage() hook.
 521  *
 522  */
 523 ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 524                                  struct pipe_inode_info *pipe, size_t len,
 525                                  unsigned int flags)
 526 {
 527         loff_t isize, left;
 528         int ret;
 529
 530         isize = i_size_read(in->f_mapping->host);
 531         if (unlikely(*ppos >= isize))
 532                 return 0;
 533
 534         left = isize - *ppos;
 535         if (unlikely(left < len))
 536                 len = left;
 537
 538         ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 539         if (ret > 0) {
 540                 *ppos += ret;
 541                 file_accessed(in);
 542         }
 543
 544         return ret;
 545 }
 546 EXPORT_SYMBOL(generic_file_splice_read);
 547
 548 static const struct pipe_buf_operations default_pipe_buf_ops = {
 549         .can_merge = 0,
 550         .map = generic_pipe_buf_map,
 551         .unmap = generic_pipe_buf_unmap,
 552         .confirm = generic_pipe_buf_confirm,
 553         .release = generic_pipe_buf_release,
 554         .steal = generic_pipe_buf_steal,
 555         .get = generic_pipe_buf_get,
 556 };
 557
 558 static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
 559                                     struct pipe_buffer *buf)
 560 {
 561         return 1;
 562 }
 563
 564 /* Pipe buffer operations for a socket and similar. */
 565 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
 566         .can_merge = 0,
 567         .map = generic_pipe_buf_map,
 568         .unmap = generic_pipe_buf_unmap,
 569         .confirm = generic_pipe_buf_confirm,
 570         .release = generic_pipe_buf_release,
 571         .steal = generic_pipe_buf_nosteal,
 572         .get = generic_pipe_buf_get,
 573 };
 574 EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 575
 576 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 577                             unsigned long vlen, loff_t offset)
 578 {
 579         mm_segment_t old_fs;
 580         loff_t pos = offset;
 581         ssize_t res;
 582
 583         old_fs = get_fs();
 584         set_fs(get_ds());
 585         /* The cast to a user pointer is valid due to the set_fs() */
 586         res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 587         set_fs(old_fs);
 588
 589         return res;
 590 }
 591
 592 ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 593                             loff_t pos)
 594 {
 595         mm_segment_t old_fs;
 596         ssize_t res;
 597
 598         old_fs = get_fs();
 599         set_fs(get_ds());
 600         /* The cast to a user pointer is valid due to the set_fs() */
 601         res = vfs_write(file, (__force const char __user *)buf, count, &pos);
 602         set_fs(old_fs);
 603
 604         return res;
 605 }
 606 EXPORT_SYMBOL(kernel_write);
 607
 608 ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 609                                  struct pipe_inode_info *pipe, size_t len,
 610                                  unsigned int flags)
 611 {
 612         unsigned int nr_pages;
 613         unsigned int nr_freed;
 614         size_t offset;
 615         struct page *pages[PIPE_DEF_BUFFERS];
 616         struct partial_page partial[PIPE_DEF_BUFFERS];
 617         struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 618         ssize_t res;
 619         size_t this_len;
 620         int error;
 621         int i;
 622         struct splice_pipe_desc spd = {
 623                 .pages = pages,
 624                 .partial = partial,
 625                 .nr_pages_max = PIPE_DEF_BUFFERS,
 626                 .flags = flags,
 627                 .ops = &default_pipe_buf_ops,
 628                 .spd_release = spd_release_page,
 629         };
 630
 631         if (splice_grow_spd(pipe, &spd))
 632                 return -ENOMEM;
 633
 634         res = -ENOMEM;
 635         vec = __vec;
 636         if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
 637                 vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
 638                 if (!vec)
 639                         goto shrink_ret;
 640         }
 641
 642         offset = *ppos & ~PAGE_CACHE_MASK;
 643         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 644
 645         for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
 646                 struct page *page;
 647
 648                 page = alloc_page(GFP_USER);
 649                 error = -ENOMEM;
 650                 if (!page)
 651                         goto err;
 652
 653                 this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 654                 vec[i].iov_base = (void __user *) page_address(page);
 655                 vec[i].iov_len = this_len;
 656                 spd.pages[i] = page;
 657                 spd.nr_pages++;
 658                 len -= this_len;
 659                 offset = 0;
 660         }
 661
 662         res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 663         if (res < 0) {
 664                 error = res;
 665                 goto err;
 666         }
 667
 668         error = 0;
 669         if (!res)
 670                 goto err;
 671
 672         nr_freed = 0;
 673         for (i = 0; i < spd.nr_pages; i++) {
 674                 this_len = min_t(size_t, vec[i].iov_len, res);
 675                 spd.partial[i].offset = 0;
 676                 spd.partial[i].len = this_len;
 677                 if (!this_len) {
 678                         __free_page(spd.pages[i]);
 679                         spd.pages[i] = NULL;
 680                         nr_freed++;
 681                 }
 682                 res -= this_len;
 683         }
 684         spd.nr_pages -= nr_freed;
 685
 686         res = splice_to_pipe(pipe, &spd);
 687         if (res > 0)
 688                 *ppos += res;
 689
 690 shrink_ret:
 691         if (vec != __vec)
 692                 kfree(vec);
 693         splice_shrink_spd(&spd);
 694         return res;
 695
 696 err:
 697         for (i = 0; i < spd.nr_pages; i++)
 698                 __free_page(spd.pages[i]);
 699
 700         res = error;
 701         goto shrink_ret;
 702 }
 703 EXPORT_SYMBOL(default_file_splice_read);
 704
 705 /*
 706  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 707  * using sendpage(). Return the number of bytes sent.
 708  */
 709 static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 710                             struct pipe_buffer *buf, struct splice_desc *sd)
 711 {
 712         struct file *file = sd->u.file;
 713         loff_t pos = sd->pos;
 714         int more;
 715
 716         if (!likely(file->f_op && file->f_op->sendpage))
 717                 return -EINVAL;
 718
 719         more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
 720
 721         if (sd->len < sd->total_len && pipe->nrbufs > 1)
 722                 more |= MSG_SENDPAGE_NOTLAST;
 723
 724         return file->f_op->sendpage(file, buf->page, buf->offset,
 725                                     sd->len, &pos, more);
 726 }
 727
 728 /*
 729  * This is a little more tricky than the file -> pipe splicing. There are
 730  * basically three cases:
 731  *
 732  *      - Destination page already exists in the address space and there
 733  *        are users of it. For that case we have no other option that
 734  *        copying the data. Tough luck.
 735  *      - Destination page already exists in the address space, but there
 736  *        are no users of it. Make sure it's uptodate, then drop it. Fall
 737  *        through to last case.
 738  *      - Destination page does not exist, we can add the pipe page to
 739  *        the page cache and avoid the copy.
 740  *
 741  * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 742  * sd->flags), we attempt to migrate pages from the pipe to the output
 743  * file address space page cache. This is possible if no one else has
 744  * the pipe page referenced outside of the pipe and page cache. If
 745  * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 746  * a new page in the output file page cache and fill/dirty that.
 747  */
 748 int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 749                  struct splice_desc *sd)
 750 {
 751         struct file *file = sd->u.file;
 752         struct address_space *mapping = file->f_mapping;
 753         unsigned int offset, this_len;
 754         struct page *page;
 755         void *fsdata;
 756         int ret;
 757
 758         offset = sd->pos & ~PAGE_CACHE_MASK;
 759
 760         this_len = sd->len;
 761         if (this_len + offset > PAGE_CACHE_SIZE)
 762                 this_len = PAGE_CACHE_SIZE - offset;
 763
 764         ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 765                                 AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 766         if (unlikely(ret))
 767                 goto out;
 768
 769         if (buf->page != page) {
 770                 char *src = buf->ops->map(pipe, buf, 1);
 771                 char *dst = kmap_atomic(page);
 772
 773                 memcpy(dst + offset, src + buf->offset, this_len);
 774                 flush_dcache_page(page);
 775                 kunmap_atomic(dst);
 776                 buf->ops->unmap(pipe, buf, src);
 777         }
 778         ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 779                                 page, fsdata);
 780 out:
 781         return ret;
 782 }
 783 EXPORT_SYMBOL(pipe_to_file);
 784
 785 static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 786 {
 787         smp_mb();
 788         if (waitqueue_active(&pipe->wait))
 789                 wake_up_interruptible(&pipe->wait);
 790         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 791 }
 792
 793 /**
 794  * splice_from_pipe_feed - feed available data from a pipe to a file
 795  * @pipe:       pipe to splice from
 796  * @sd:         information to @actor
 797  * @actor:      handler that splices the data
 798  *
 799  * Description:
 800  *    This function loops over the pipe and calls @actor to do the
 801  *    actual moving of a single struct pipe_buffer to the desired
 802  *    destination.  It returns when there's no more buffers left in
 803  *    the pipe or if the requested number of bytes (@sd->total_len)
 804  *    have been copied.  It returns a positive number (one) if the
 805  *    pipe needs to be filled with more data, zero if the required
 806  *    number of bytes have been copied and -errno on error.
 807  *
 808  *    This, together with splice_from_pipe_{begin,end,next}, may be
 809  *    used to implement the functionality of __splice_from_pipe() when
 810  *    locking is required around copying the pipe buffers to the
 811  *    destination.
 812  */
 813 int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 814                           splice_actor *actor)
 815 {
 816         int ret;
 817
 818         while (pipe->nrbufs) {
 819                 struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 820                 const struct pipe_buf_operations *ops = buf->ops;
 821
 822                 sd->len = buf->len;
 823                 if (sd->len > sd->total_len)
 824                         sd->len = sd->total_len;
 825
 826                 ret = buf->ops->confirm(pipe, buf);
 827                 if (unlikely(ret)) {
 828                         if (ret == -ENODATA)
 829                                 ret = 0;
 830                         return ret;
 831                 }
 832
 833                 ret = actor(pipe, buf, sd);
 834                 if (ret <= 0)
 835                         return ret;
 836
 837                 buf->offset += ret;
 838                 buf->len -= ret;
 839
 840                 sd->num_spliced += ret;
 841                 sd->len -= ret;
 842                 sd->pos += ret;
 843                 sd->total_len -= ret;
 844
 845                 if (!buf->len) {
 846                         buf->ops = NULL;
 847                         ops->release(pipe, buf);
 848                         pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 849                         pipe->nrbufs--;
 850                         if (pipe->files)
 851                                 sd->need_wakeup = true;
 852                 }
 853
 854                 if (!sd->total_len)
 855                         return 0;
 856         }
 857
 858         return 1;
 859 }
 860 EXPORT_SYMBOL(splice_from_pipe_feed);
 861
 862 /**
 863  * splice_from_pipe_next - wait for some data to splice from
 864  * @pipe:       pipe to splice from
 865  * @sd:         information about the splice operation
 866  *
 867  * Description:
 868  *    This function will wait for some data and return a positive
 869  *    value (one) if pipe buffers are available.  It will return zero
 870  *    or -errno if no more data needs to be spliced.
 871  */
 872 int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 873 {
 874         while (!pipe->nrbufs) {
 875                 if (!pipe->writers)
 876                         return 0;
 877
 878                 if (!pipe->waiting_writers && sd->num_spliced)
 879                         return 0;
 880
 881                 if (sd->flags & SPLICE_F_NONBLOCK)
 882                         return -EAGAIN;
 883
 884                 if (signal_pending(current))
 885                         return -ERESTARTSYS;
 886
 887                 if (sd->need_wakeup) {
 888                         wakeup_pipe_writers(pipe);
 889                         sd->need_wakeup = false;
 890                 }
 891
 892                 pipe_wait(pipe);
 893         }
 894
 895         return 1;
 896 }
 897 EXPORT_SYMBOL(splice_from_pipe_next);
 898
 899 /**
 900  * splice_from_pipe_begin - start splicing from pipe
 901  * @sd:         information about the splice operation
 902  *
 903  * Description:
 904  *    This function should be called before a loop containing
 905  *    splice_from_pipe_next() and splice_from_pipe_feed() to
 906  *    initialize the necessary fields of @sd.
 907  */
 908 void splice_from_pipe_begin(struct splice_desc *sd)
 909 {
 910         sd->num_spliced = 0;
 911         sd->need_wakeup = false;
 912 }
 913 EXPORT_SYMBOL(splice_from_pipe_begin);
 914
 915 /**
 916  * splice_from_pipe_end - finish splicing from pipe
 917  * @pipe:       pipe to splice from
 918  * @sd:         information about the splice operation
 919  *
 920  * Description:
 921  *    This function will wake up pipe writers if necessary.  It should
 922  *    be called after a loop containing splice_from_pipe_next() and
 923  *    splice_from_pipe_feed().
 924  */
 925 void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 926 {
 927         if (sd->need_wakeup)
 928                 wakeup_pipe_writers(pipe);
 929 }
 930 EXPORT_SYMBOL(splice_from_pipe_end);
 931
 932 /**
 933  * __splice_from_pipe - splice data from a pipe to given actor
 934  * @pipe:       pipe to splice from
 935  * @sd:         information to @actor
 936  * @actor:      handler that splices the data
 937  *
 938  * Description:
 939  *    This function does little more than loop over the pipe and call
 940  *    @actor to do the actual moving of a single struct pipe_buffer to
 941  *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 942  *    pipe_to_user.
 943  *
 944  */
 945 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 946                            splice_actor *actor)
 947 {
 948         int ret;
 949
 950         splice_from_pipe_begin(sd);
 951         do {
 952                 ret = splice_from_pipe_next(pipe, sd);
 953                 if (ret > 0)
 954                         ret = splice_from_pipe_feed(pipe, sd, actor);
 955         } while (ret > 0);
 956         splice_from_pipe_end(pipe, sd);
 957
 958         return sd->num_spliced ? sd->num_spliced : ret;
 959 }
 960 EXPORT_SYMBOL(__splice_from_pipe);
 961
 962 /**
 963  * splice_from_pipe - splice data from a pipe to a file
 964  * @pipe:       pipe to splice from
 965  * @out:        file to splice to
 966  * @ppos:       position in @out
 967  * @len:        how many bytes to splice
 968  * @flags:      splice modifier flags
 969  * @actor:      handler that splices the data
 970  *
 971  * Description:
 972  *    See __splice_from_pipe. This function locks the pipe inode,
 973  *    otherwise it's identical to __splice_from_pipe().
 974  *
 975  */
 976 ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 977                          loff_t *ppos, size_t len, unsigned int flags,
 978                          splice_actor *actor)
 979 {
 980         ssize_t ret;
 981         struct splice_desc sd = {
 982                 .total_len = len,
 983                 .flags = flags,
 984                 .pos = *ppos,
 985                 .u.file = out,
 986         };
 987
 988         pipe_lock(pipe);
 989         ret = __splice_from_pipe(pipe, &sd, actor);
 990         pipe_unlock(pipe);
 991
 992         return ret;
 993 }
 994
 995 /**
 996  * generic_file_splice_write - splice data from a pipe to a file
 997  * @pipe:       pipe info
 998  * @out:        file to write to
 999  * @ppos:       position in @out
1000  * @len:        number of bytes to splice
1001  * @flags:      splice modifier flags
1002  *
1003  * Description:
1004  *    Will either move or copy pages (determined by @flags options) from
1005  *    the given pipe inode to the given file.
1006  *
1007  */
1008 ssize_t
1009 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
1010                           loff_t *ppos, size_t len, unsigned int flags)
1011 {
1012         struct address_space *mapping = out->f_mapping;
1013         struct inode *inode = mapping->host;
1014         struct splice_desc sd = {
1015                 .flags = flags,
1016                 .u.file = out,
1017         };
1018         ssize_t ret;
1019
1020         ret = generic_write_checks(out, ppos, &len, S_ISBLK(inode->i_mode));
1021         if (ret)
1022                 return ret;
1023         sd.total_len = len;
1024         sd.pos = *ppos;
1025
1026         pipe_lock(pipe);
1027
1028         splice_from_pipe_begin(&sd);
1029         do {
1030                 ret = splice_from_pipe_next(pipe, &sd);
1031                 if (ret <= 0)
1032                         break;
1033
1034                 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1035                 ret = file_remove_suid(out);
1036                 if (!ret) {
1037                         ret = file_update_time(out);
1038                         if (!ret)
1039                                 ret = splice_from_pipe_feed(pipe, &sd,
1040                                                             pipe_to_file);
1041                 }
1042                 mutex_unlock(&inode->i_mutex);
1043         } while (ret > 0);
1044         splice_from_pipe_end(pipe, &sd);
1045
1046         pipe_unlock(pipe);
1047
1048         if (sd.num_spliced)
1049                 ret = sd.num_spliced;
1050
1051         if (ret > 0) {
1052                 int err;
1053
1054                 err = generic_write_sync(out, *ppos, ret);
1055                 if (err)
1056                         ret = err;
1057                 else
1058                         *ppos += ret;
1059                 balance_dirty_pages_ratelimited(mapping);
1060         }
1061
1062         return ret;
1063 }
1064
1065 EXPORT_SYMBOL(generic_file_splice_write);
1066
1067 static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1068                           struct splice_desc *sd)
1069 {
1070         int ret;
1071         void *data;
1072         loff_t tmp = sd->pos;
1073
1074         data = buf->ops->map(pipe, buf, 0);
1075         ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1076         buf->ops->unmap(pipe, buf, data);
1077
1078         return ret;
1079 }
1080
1081 static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1082                                          struct file *out, loff_t *ppos,
1083                                          size_t len, unsigned int flags)
1084 {
1085         ssize_t ret;
1086
1087         ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1088         if (ret > 0)
1089                 *ppos += ret;
1090
1091         return ret;
1092 }
1093
1094 /**
1095  * generic_splice_sendpage - splice data from a pipe to a socket
1096  * @pipe:       pipe to splice from
1097  * @out:        socket to write to
1098  * @ppos:       position in @out
1099  * @len:        number of bytes to splice
1100  * @flags:      splice modifier flags
1101  *
1102  * Description:
1103  *    Will send @len bytes from the pipe to a network socket. No data copying
1104  *    is involved.
1105  *
1106  */
1107 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1108                                 loff_t *ppos, size_t len, unsigned int flags)
1109 {
1110         return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1111 }
1112
1113 EXPORT_SYMBOL(generic_splice_sendpage);
1114
1115 /*
1116  * Attempt to initiate a splice from pipe to file.
1117  */
1118 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1119                            loff_t *ppos, size_t len, unsigned int flags)
1120 {
1121         ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1122                                 loff_t *, size_t, unsigned int);
1123         int ret;
1124
1125         if (unlikely(!(out->f_mode & FMODE_WRITE)))
1126                 return -EBADF;
1127
1128         if (unlikely(out->f_flags & O_APPEND))
1129                 return -EINVAL;
1130
1131         ret = rw_verify_area(WRITE, out, ppos, len);
1132         if (unlikely(ret < 0))
1133                 return ret;
1134
1135         if (out->f_op && out->f_op->splice_write)
1136                 splice_write = out->f_op->splice_write;
1137         else
1138                 splice_write = default_file_splice_write;
1139
1140         file_start_write(out);
1141         ret = splice_write(pipe, out, ppos, len, flags);
1142         file_end_write(out);
1143         return ret;
1144 }
1145
1146 /*
1147  * Attempt to initiate a splice from a file to a pipe.
1148  */
1149 static long do_splice_to(struct file *in, loff_t *ppos,
1150                          struct pipe_inode_info *pipe, size_t len,
1151                          unsigned int flags)
1152 {
1153         ssize_t (*splice_read)(struct file *, loff_t *,
1154                                struct pipe_inode_info *, size_t, unsigned int);
1155         int ret;
1156
1157         if (unlikely(!(in->f_mode & FMODE_READ)))
1158                 return -EBADF;
1159
1160         ret = rw_verify_area(READ, in, ppos, len);
1161         if (unlikely(ret < 0))
1162                 return ret;
1163
1164         if (in->f_op && in->f_op->splice_read)
1165                 splice_read = in->f_op->splice_read;
1166         else
1167                 splice_read = default_file_splice_read;
1168
1169         return splice_read(in, ppos, pipe, len, flags);
1170 }
1171
1172 /**
1173  * splice_direct_to_actor - splices data directly between two non-pipes
1174  * @in:         file to splice from
1175  * @sd:         actor information on where to splice to
1176  * @actor:      handles the data splicing
1177  *
1178  * Description:
1179  *    This is a special case helper to splice directly between two
1180  *    points, without requiring an explicit pipe. Internally an allocated
1181  *    pipe is cached in the process, and reused during the lifetime of
1182  *    that process.
1183  *
1184  */
1185 ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1186                                splice_direct_actor *actor)
1187 {
1188         struct pipe_inode_info *pipe;
1189         long ret, bytes;
1190         umode_t i_mode;
1191         size_t len;
1192         int i, flags;
1193
1194         /*
1195          * We require the input being a regular file, as we don't want to
1196          * randomly drop data for eg socket -> socket splicing. Use the
1197          * piped splicing for that!
1198          */
1199         i_mode = file_inode(in)->i_mode;
1200         if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1201                 return -EINVAL;
1202
1203         /*
1204          * neither in nor out is a pipe, setup an internal pipe attached to
1205          * 'out' and transfer the wanted data from 'in' to 'out' through that
1206          */
1207         pipe = current->splice_pipe;
1208         if (unlikely(!pipe)) {
1209                 pipe = alloc_pipe_info();
1210                 if (!pipe)
1211                         return -ENOMEM;
1212
1213                 /*
1214                  * We don't have an immediate reader, but we'll read the stuff
1215                  * out of the pipe right after the splice_to_pipe(). So set
1216                  * PIPE_READERS appropriately.
1217                  */
1218                 pipe->readers = 1;
1219
1220                 current->splice_pipe = pipe;
1221         }
1222
1223         /*
1224          * Do the splice.
1225          */
1226         ret = 0;
1227         bytes = 0;
1228         len = sd->total_len;
1229         flags = sd->flags;
1230
1231         /*
1232          * Don't block on output, we have to drain the direct pipe.
1233          */
1234         sd->flags &= ~SPLICE_F_NONBLOCK;
1235
1236         while (len) {
1237                 size_t read_len;
1238                 loff_t pos = sd->pos, prev_pos = pos;
1239
1240                 ret = do_splice_to(in, &pos, pipe, len, flags);
1241                 if (unlikely(ret <= 0))
1242                         goto out_release;
1243
1244                 read_len = ret;
1245                 sd->total_len = read_len;
1246
1247                 /*
1248                  * NOTE: nonblocking mode only applies to the input. We
1249                  * must not do the output in nonblocking mode as then we
1250                  * could get stuck data in the internal pipe:
1251                  */
1252                 ret = actor(pipe, sd);
1253                 if (unlikely(ret <= 0)) {
1254                         sd->pos = prev_pos;
1255                         goto out_release;
1256                 }
1257
1258                 bytes += ret;
1259                 len -= ret;
1260                 sd->pos = pos;
1261
1262                 if (ret < read_len) {
1263                         sd->pos = prev_pos + ret;
1264                         goto out_release;
1265                 }
1266         }
1267
1268 done:
1269         pipe->nrbufs = pipe->curbuf = 0;
1270         file_accessed(in);
1271         return bytes;
1272
1273 out_release:
1274         /*
1275          * If we did an incomplete transfer we must release
1276          * the pipe buffers in question:
1277          */
1278         for (i = 0; i < pipe->buffers; i++) {
1279                 struct pipe_buffer *buf = pipe->bufs + i;
1280
1281                 if (buf->ops) {
1282                         buf->ops->release(pipe, buf);
1283                         buf->ops = NULL;
1284                 }
1285         }
1286
1287         if (!bytes)
1288                 bytes = ret;
1289
1290         goto done;
1291 }
1292 EXPORT_SYMBOL(splice_direct_to_actor);
1293
1294 static int direct_splice_actor(struct pipe_inode_info *pipe,
1295                                struct splice_desc *sd)
1296 {
1297         struct file *file = sd->u.file;
1298
1299         return do_splice_from(pipe, file, sd->opos, sd->total_len,
1300                               sd->flags);
1301 }
1302
1303 /**
1304  * do_splice_direct - splices data directly between two files
1305  * @in:         file to splice from
1306  * @ppos:       input file offset
1307  * @out:        file to splice to
1308  * @opos:       output file offset
1309  * @len:        number of bytes to splice
1310  * @flags:      splice modifier flags
1311  *
1312  * Description:
1313  *    For use by do_sendfile(). splice can easily emulate sendfile, but
1314  *    doing it in the application would incur an extra system call
1315  *    (splice in + splice out, as compared to just sendfile()). So this helper
1316  *    can splice directly through a process-private pipe.
1317  *
1318  */
1319 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1320                       loff_t *opos, size_t len, unsigned int flags)
1321 {
1322         struct splice_desc sd = {
1323                 .len            = len,
1324                 .total_len      = len,
1325                 .flags          = flags,
1326                 .pos            = *ppos,
1327                 .u.file         = out,
1328                 .opos           = opos,
1329         };
1330         long ret;
1331
1332         ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1333         if (ret > 0)
1334                 *ppos = sd.pos;
1335
1336         return ret;
1337 }
1338
1339 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1340                                struct pipe_inode_info *opipe,
1341                                size_t len, unsigned int flags);
1342
1343 /*
1344  * Determine where to splice to/from.
1345  */
1346 static long do_splice(struct file *in, loff_t __user *off_in,
1347                       struct file *out, loff_t __user *off_out,
1348                       size_t len, unsigned int flags)
1349 {
1350         struct pipe_inode_info *ipipe;
1351         struct pipe_inode_info *opipe;
1352         loff_t offset;
1353         long ret;
1354
1355         ipipe = get_pipe_info(in);
1356         opipe = get_pipe_info(out);
1357
1358         if (ipipe && opipe) {
1359                 if (off_in || off_out)
1360                         return -ESPIPE;
1361
1362                 if (!(in->f_mode & FMODE_READ))
1363                         return -EBADF;
1364
1365                 if (!(out->f_mode & FMODE_WRITE))
1366                         return -EBADF;
1367
1368                 /* Splicing to self would be fun, but... */
1369                 if (ipipe == opipe)
1370                         return -EINVAL;
1371
1372                 return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1373         }
1374
1375         if (ipipe) {
1376                 if (off_in)
1377                         return -ESPIPE;
1378                 if (off_out) {
1379                         if (!(out->f_mode & FMODE_PWRITE))
1380                                 return -EINVAL;
1381                         if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1382                                 return -EFAULT;
1383                 } else {
1384                         offset = out->f_pos;
1385                 }
1386
1387                 ret = do_splice_from(ipipe, out, &offset, len, flags);
1388
1389                 if (!off_out)
1390                         out->f_pos = offset;
1391                 else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1392                         ret = -EFAULT;
1393
1394                 return ret;
1395         }
1396
1397         if (opipe) {
1398                 if (off_out)
1399                         return -ESPIPE;
1400                 if (off_in) {
1401                         if (!(in->f_mode & FMODE_PREAD))
1402                                 return -EINVAL;
1403                         if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1404                                 return -EFAULT;
1405                 } else {
1406                         offset = in->f_pos;
1407                 }
1408
1409                 ret = do_splice_to(in, &offset, opipe, len, flags);
1410
1411                 if (!off_in)
1412                         in->f_pos = offset;
1413                 else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1414                         ret = -EFAULT;
1415
1416                 return ret;
1417         }
1418
1419         return -EINVAL;
1420 }
1421
1422 /*
1423  * Map an iov into an array of pages and offset/length tupples. With the
1424  * partial_page structure, we can map several non-contiguous ranges into
1425  * our ones pages[] map instead of splitting that operation into pieces.
1426  * Could easily be exported as a generic helper for other users, in which
1427  * case one would probably want to add a 'max_nr_pages' parameter as well.
1428  */
1429 static int get_iovec_page_array(const struct iovec __user *iov,
1430                                 unsigned int nr_vecs, struct page **pages,
1431                                 struct partial_page *partial, bool aligned,
1432                                 unsigned int pipe_buffers)
1433 {
1434         int buffers = 0, error = 0;
1435
1436         while (nr_vecs) {
1437                 unsigned long off, npages;
1438                 struct iovec entry;
1439                 void __user *base;
1440                 size_t len;
1441                 int i;
1442
1443                 error = -EFAULT;
1444                 if (copy_from_user(&entry, iov, sizeof(entry)))
1445                         break;
1446
1447                 base = entry.iov_base;
1448                 len = entry.iov_len;
1449
1450                 /*
1451                  * Sanity check this iovec. 0 read succeeds.
1452                  */
1453                 error = 0;
1454                 if (unlikely(!len))
1455                         break;
1456                 error = -EFAULT;
1457                 if (!access_ok(VERIFY_READ, base, len))
1458                         break;
1459
1460                 /*
1461                  * Get this base offset and number of pages, then map
1462                  * in the user pages.
1463                  */
1464                 off = (unsigned long) base & ~PAGE_MASK;
1465
1466                 /*
1467                  * If asked for alignment, the offset must be zero and the
1468                  * length a multiple of the PAGE_SIZE.
1469                  */
1470                 error = -EINVAL;
1471                 if (aligned && (off || len & ~PAGE_MASK))
1472                         break;
1473
1474                 npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1475                 if (npages > pipe_buffers - buffers)
1476                         npages = pipe_buffers - buffers;
1477
1478                 error = get_user_pages_fast((unsigned long)base, npages,
1479                                         0, &pages[buffers]);
1480
1481                 if (unlikely(error <= 0))
1482                         break;
1483
1484                 /*
1485                  * Fill this contiguous range into the partial page map.
1486                  */
1487                 for (i = 0; i < error; i++) {
1488                         const int plen = min_t(size_t, len, PAGE_SIZE - off);
1489
1490                         partial[buffers].offset = off;
1491                         partial[buffers].len = plen;
1492
1493                         off = 0;
1494                         len -= plen;
1495                         buffers++;
1496                 }
1497
1498                 /*
1499                  * We didn't complete this iov, stop here since it probably
1500                  * means we have to move some of this into a pipe to
1501                  * be able to continue.
1502                  */
1503                 if (len)
1504                         break;
1505
1506                 /*
1507                  * Don't continue if we mapped fewer pages than we asked for,
1508                  * or if we mapped the max number of pages that we have
1509                  * room for.
1510                  */
1511                 if (error < npages || buffers == pipe_buffers)
1512                         break;
1513
1514                 nr_vecs--;
1515                 iov++;
1516         }
1517
1518         if (buffers)
1519                 return buffers;
1520
1521         return error;
1522 }
1523
1524 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1525                         struct splice_desc *sd)
1526 {
1527         char *src;
1528         int ret;
1529
1530         /*
1531          * See if we can use the atomic maps, by prefaulting in the
1532          * pages and doing an atomic copy
1533          */
1534         if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1535                 src = buf->ops->map(pipe, buf, 1);
1536                 ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1537                                                         sd->len);
1538                 buf->ops->unmap(pipe, buf, src);
1539                 if (!ret) {
1540                         ret = sd->len;
1541                         goto out;
1542                 }
1543         }
1544
1545         /*
1546          * No dice, use slow non-atomic map and copy
1547          */
1548         src = buf->ops->map(pipe, buf, 0);
1549
1550         ret = sd->len;
1551         if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1552                 ret = -EFAULT;
1553
1554         buf->ops->unmap(pipe, buf, src);
1555 out:
1556         if (ret > 0)
1557                 sd->u.userptr += ret;
1558         return ret;
1559 }
1560
1561 /*
1562  * For lack of a better implementation, implement vmsplice() to userspace
1563  * as a simple copy of the pipes pages to the user iov.
1564  */
1565 static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1566                              unsigned long nr_segs, unsigned int flags)
1567 {
1568         struct pipe_inode_info *pipe;
1569         struct splice_desc sd;
1570         ssize_t size;
1571         int error;
1572         long ret;
1573
1574         pipe = get_pipe_info(file);
1575         if (!pipe)
1576                 return -EBADF;
1577
1578         pipe_lock(pipe);
1579
1580         error = ret = 0;
1581         while (nr_segs) {
1582                 void __user *base;
1583                 size_t len;
1584
1585                 /*
1586                  * Get user address base and length for this iovec.
1587                  */
1588                 error = get_user(base, &iov->iov_base);
1589                 if (unlikely(error))
1590                         break;
1591                 error = get_user(len, &iov->iov_len);
1592                 if (unlikely(error))
1593                         break;
1594
1595                 /*
1596                  * Sanity check this iovec. 0 read succeeds.
1597                  */
1598                 if (unlikely(!len))
1599                         break;
1600                 if (unlikely(!base)) {
1601                         error = -EFAULT;
1602                         break;
1603                 }
1604
1605                 if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1606                         error = -EFAULT;
1607                         break;
1608                 }
1609
1610                 sd.len = 0;
1611                 sd.total_len = len;
1612                 sd.flags = flags;
1613                 sd.u.userptr = base;
1614                 sd.pos = 0;
1615
1616                 size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1617                 if (size < 0) {
1618                         if (!ret)
1619                                 ret = size;
1620
1621                         break;
1622                 }
1623
1624                 ret += size;
1625
1626                 if (size < len)
1627                         break;
1628
1629                 nr_segs--;
1630                 iov++;
1631         }
1632
1633         pipe_unlock(pipe);
1634
1635         if (!ret)
1636                 ret = error;
1637
1638         return ret;
1639 }
1640
1641 /*
1642  * vmsplice splices a user address range into a pipe. It can be thought of
1643  * as splice-from-memory, where the regular splice is splice-from-file (or
1644  * to file). In both cases the output is a pipe, naturally.
1645  */
1646 static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1647                              unsigned long nr_segs, unsigned int flags)
1648 {
1649         struct pipe_inode_info *pipe;
1650         struct page *pages[PIPE_DEF_BUFFERS];
1651         struct partial_page partial[PIPE_DEF_BUFFERS];
1652         struct splice_pipe_desc spd = {
1653                 .pages = pages,
1654                 .partial = partial,
1655                 .nr_pages_max = PIPE_DEF_BUFFERS,
1656                 .flags = flags,
1657                 .ops = &user_page_pipe_buf_ops,
1658                 .spd_release = spd_release_page,
1659         };
1660         long ret;
1661
1662         pipe = get_pipe_info(file);
1663         if (!pipe)
1664                 return -EBADF;
1665
1666         if (splice_grow_spd(pipe, &spd))
1667                 return -ENOMEM;
1668
1669         spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1670                                             spd.partial, false,
1671                                             spd.nr_pages_max);
1672         if (spd.nr_pages <= 0)
1673                 ret = spd.nr_pages;
1674         else
1675                 ret = splice_to_pipe(pipe, &spd);
1676
1677         splice_shrink_spd(&spd);
1678         return ret;
1679 }
1680
1681 /*
1682  * Note that vmsplice only really supports true splicing _from_ user memory
1683  * to a pipe, not the other way around. Splicing from user memory is a simple
1684  * operation that can be supported without any funky alignment restrictions
1685  * or nasty vm tricks. We simply map in the user memory and fill them into
1686  * a pipe. The reverse isn't quite as easy, though. There are two possible
1687  * solutions for that:
1688  *
1689  *      - memcpy() the data internally, at which point we might as well just
1690  *        do a regular read() on the buffer anyway.
1691  *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1692  *        has restriction limitations on both ends of the pipe).
1693  *
1694  * Currently we punt and implement it as a normal copy, see pipe_to_user().
1695  *
1696  */
1697 SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1698                 unsigned long, nr_segs, unsigned int, flags)
1699 {
1700         struct fd f;
1701         long error;
1702
1703         if (unlikely(nr_segs > UIO_MAXIOV))
1704                 return -EINVAL;
1705         else if (unlikely(!nr_segs))
1706                 return 0;
1707
1708         error = -EBADF;
1709         f = fdget(fd);
1710         if (f.file) {
1711                 if (f.file->f_mode & FMODE_WRITE)
1712                         error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1713                 else if (f.file->f_mode & FMODE_READ)
1714                         error = vmsplice_to_user(f.file, iov, nr_segs, flags);
1715
1716                 fdput(f);
1717         }
1718
1719         return error;
1720 }
1721
1722 #ifdef CONFIG_COMPAT
1723 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1724                     unsigned int, nr_segs, unsigned int, flags)
1725 {
1726         unsigned i;
1727         struct iovec __user *iov;
1728         if (nr_segs > UIO_MAXIOV)
1729                 return -EINVAL;
1730         iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1731         for (i = 0; i < nr_segs; i++) {
1732                 struct compat_iovec v;
1733                 if (get_user(v.iov_base, &iov32[i].iov_base) ||
1734                     get_user(v.iov_len, &iov32[i].iov_len) ||
1735                     put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1736                     put_user(v.iov_len, &iov[i].iov_len))
1737                         return -EFAULT;
1738         }
1739         return sys_vmsplice(fd, iov, nr_segs, flags);
1740 }
1741 #endif
1742
1743 SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1744                 int, fd_out, loff_t __user *, off_out,
1745                 size_t, len, unsigned int, flags)
1746 {
1747         struct fd in, out;
1748         long error;
1749
1750         if (unlikely(!len))
1751                 return 0;
1752
1753         error = -EBADF;
1754         in = fdget(fd_in);
1755         if (in.file) {
1756                 if (in.file->f_mode & FMODE_READ) {
1757                         out = fdget(fd_out);
1758                         if (out.file) {
1759                                 if (out.file->f_mode & FMODE_WRITE)
1760                                         error = do_splice(in.file, off_in,
1761                                                           out.file, off_out,
1762                                                           len, flags);
1763                                 fdput(out);
1764                         }
1765                 }
1766                 fdput(in);
1767         }
1768         return error;
1769 }
1770
1771 /*
1772  * Make sure there's data to read. Wait for input if we can, otherwise
1773  * return an appropriate error.
1774  */
1775 static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1776 {
1777         int ret;
1778
1779         /*
1780          * Check ->nrbufs without the inode lock first. This function
1781          * is speculative anyways, so missing one is ok.
1782          */
1783         if (pipe->nrbufs)
1784                 return 0;
1785
1786         ret = 0;
1787         pipe_lock(pipe);
1788
1789         while (!pipe->nrbufs) {
1790                 if (signal_pending(current)) {
1791                         ret = -ERESTARTSYS;
1792                         break;
1793                 }
1794                 if (!pipe->writers)
1795                         break;
1796                 if (!pipe->waiting_writers) {
1797                         if (flags & SPLICE_F_NONBLOCK) {
1798                                 ret = -EAGAIN;
1799                                 break;
1800                         }
1801                 }
1802                 pipe_wait(pipe);
1803         }
1804
1805         pipe_unlock(pipe);
1806         return ret;
1807 }
1808
1809 /*
1810  * Make sure there's writeable room. Wait for room if we can, otherwise
1811  * return an appropriate error.
1812  */
1813 static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1814 {
1815         int ret;
1816
1817         /*
1818          * Check ->nrbufs without the inode lock first. This function
1819          * is speculative anyways, so missing one is ok.
1820          */
1821         if (pipe->nrbufs < pipe->buffers)
1822                 return 0;
1823
1824         ret = 0;
1825         pipe_lock(pipe);
1826
1827         while (pipe->nrbufs >= pipe->buffers) {
1828                 if (!pipe->readers) {
1829                         send_sig(SIGPIPE, current, 0);
1830                         ret = -EPIPE;
1831                         break;
1832                 }
1833                 if (flags & SPLICE_F_NONBLOCK) {
1834                         ret = -EAGAIN;
1835                         break;
1836                 }
1837                 if (signal_pending(current)) {
1838                         ret = -ERESTARTSYS;
1839                         break;
1840                 }
1841                 pipe->waiting_writers++;
1842                 pipe_wait(pipe);
1843                 pipe->waiting_writers--;
1844         }
1845
1846         pipe_unlock(pipe);
1847         return ret;
1848 }
1849
1850 /*
1851  * Splice contents of ipipe to opipe.
1852  */
1853 static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1854                                struct pipe_inode_info *opipe,
1855                                size_t len, unsigned int flags)
1856 {
1857         struct pipe_buffer *ibuf, *obuf;
1858         int ret = 0, nbuf;
1859         bool input_wakeup = false;
1860
1861
1862 retry:
1863         ret = ipipe_prep(ipipe, flags);
1864         if (ret)
1865                 return ret;
1866
1867         ret = opipe_prep(opipe, flags);
1868         if (ret)
1869                 return ret;
1870
1871         /*
1872          * Potential ABBA deadlock, work around it by ordering lock
1873          * grabbing by pipe info address. Otherwise two different processes
1874          * could deadlock (one doing tee from A -> B, the other from B -> A).
1875          */
1876         pipe_double_lock(ipipe, opipe);
1877
1878         do {
1879                 if (!opipe->readers) {
1880                         send_sig(SIGPIPE, current, 0);
1881                         if (!ret)
1882                                 ret = -EPIPE;
1883                         break;
1884                 }
1885
1886                 if (!ipipe->nrbufs && !ipipe->writers)
1887                         break;
1888
1889                 /*
1890                  * Cannot make any progress, because either the input
1891                  * pipe is empty or the output pipe is full.
1892                  */
1893                 if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1894                         /* Already processed some buffers, break */
1895                         if (ret)
1896                                 break;
1897
1898                         if (flags & SPLICE_F_NONBLOCK) {
1899                                 ret = -EAGAIN;
1900                                 break;
1901                         }
1902
1903                         /*
1904                          * We raced with another reader/writer and haven't
1905                          * managed to process any buffers.  A zero return
1906                          * value means EOF, so retry instead.
1907                          */
1908                         pipe_unlock(ipipe);
1909                         pipe_unlock(opipe);
1910                         goto retry;
1911                 }
1912
1913                 ibuf = ipipe->bufs + ipipe->curbuf;
1914                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1915                 obuf = opipe->bufs + nbuf;
1916
1917                 if (len >= ibuf->len) {
1918                         /*
1919                          * Simply move the whole buffer from ipipe to opipe
1920                          */
1921                         *obuf = *ibuf;
1922                         ibuf->ops = NULL;
1923                         opipe->nrbufs++;
1924                         ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1925                         ipipe->nrbufs--;
1926                         input_wakeup = true;
1927                 } else {
1928                         /*
1929                          * Get a reference to this pipe buffer,
1930                          * so we can copy the contents over.
1931                          */
1932                         ibuf->ops->get(ipipe, ibuf);
1933                         *obuf = *ibuf;
1934
1935                         /*
1936                          * Don't inherit the gift flag, we need to
1937                          * prevent multiple steals of this page.
1938                          */
1939                         obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1940
1941                         obuf->len = len;
1942                         opipe->nrbufs++;
1943                         ibuf->offset += obuf->len;
1944                         ibuf->len -= obuf->len;
1945                 }
1946                 ret += obuf->len;
1947                 len -= obuf->len;
1948         } while (len);
1949
1950         pipe_unlock(ipipe);
1951         pipe_unlock(opipe);
1952
1953         /*
1954          * If we put data in the output pipe, wakeup any potential readers.
1955          */
1956         if (ret > 0)
1957                 wakeup_pipe_readers(opipe);
1958
1959         if (input_wakeup)
1960                 wakeup_pipe_writers(ipipe);
1961
1962         return ret;
1963 }
1964
1965 /*
1966  * Link contents of ipipe to opipe.
1967  */
1968 static int link_pipe(struct pipe_inode_info *ipipe,
1969                      struct pipe_inode_info *opipe,
1970                      size_t len, unsigned int flags)
1971 {
1972         struct pipe_buffer *ibuf, *obuf;
1973         int ret = 0, i = 0, nbuf;
1974
1975         /*
1976          * Potential ABBA deadlock, work around it by ordering lock
1977          * grabbing by pipe info address. Otherwise two different processes
1978          * could deadlock (one doing tee from A -> B, the other from B -> A).
1979          */
1980         pipe_double_lock(ipipe, opipe);
1981
1982         do {
1983                 if (!opipe->readers) {
1984                         send_sig(SIGPIPE, current, 0);
1985                         if (!ret)
1986                                 ret = -EPIPE;
1987                         break;
1988                 }
1989
1990                 /*
1991                  * If we have iterated all input buffers or ran out of
1992                  * output room, break.
1993                  */
1994                 if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1995                         break;
1996
1997                 ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1998                 nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1999
2000                 /*
2001                  * Get a reference to this pipe buffer,
2002                  * so we can copy the contents over.
2003                  */
2004                 ibuf->ops->get(ipipe, ibuf);
2005
2006                 obuf = opipe->bufs + nbuf;
2007                 *obuf = *ibuf;
2008
2009                 /*
2010                  * Don't inherit the gift flag, we need to
2011                  * prevent multiple steals of this page.
2012                  */
2013                 obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
2014
2015                 if (obuf->len > len)
2016                         obuf->len = len;
2017
2018                 opipe->nrbufs++;
2019                 ret += obuf->len;
2020                 len -= obuf->len;
2021                 i++;
2022         } while (len);
2023
2024         /*
2025          * return EAGAIN if we have the potential of some data in the
2026          * future, otherwise just return 0
2027          */
2028         if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
2029                 ret = -EAGAIN;
2030
2031         pipe_unlock(ipipe);
2032         pipe_unlock(opipe);
2033
2034         /*
2035          * If we put data in the output pipe, wakeup any potential readers.
2036          */
2037         if (ret > 0)
2038                 wakeup_pipe_readers(opipe);
2039
2040         return ret;
2041 }
2042
2043 /*
2044  * This is a tee(1) implementation that works on pipes. It doesn't copy
2045  * any data, it simply references the 'in' pages on the 'out' pipe.
2046  * The 'flags' used are the SPLICE_F_* variants, currently the only
2047  * applicable one is SPLICE_F_NONBLOCK.
2048  */
2049 static long do_tee(struct file *in, struct file *out, size_t len,
2050                    unsigned int flags)
2051 {
2052         struct pipe_inode_info *ipipe = get_pipe_info(in);
2053         struct pipe_inode_info *opipe = get_pipe_info(out);
2054         int ret = -EINVAL;
2055
2056         /*
2057          * Duplicate the contents of ipipe to opipe without actually
2058          * copying the data.
2059          */
2060         if (ipipe && opipe && ipipe != opipe) {
2061                 /*
2062                  * Keep going, unless we encounter an error. The ipipe/opipe
2063                  * ordering doesn't really matter.
2064                  */
2065                 ret = ipipe_prep(ipipe, flags);
2066                 if (!ret) {
2067                         ret = opipe_prep(opipe, flags);
2068                         if (!ret)
2069                                 ret = link_pipe(ipipe, opipe, len, flags);
2070                 }
2071         }
2072
2073         return ret;
2074 }
2075
2076 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2077 {
2078         struct fd in;
2079         int error;
2080
2081         if (unlikely(!len))
2082                 return 0;
2083
2084         error = -EBADF;
2085         in = fdget(fdin);
2086         if (in.file) {
2087                 if (in.file->f_mode & FMODE_READ) {
2088                         struct fd out = fdget(fdout);
2089                         if (out.file) {
2090                                 if (out.file->f_mode & FMODE_WRITE)
2091                                         error = do_tee(in.file, out.file,
2092                                                         len, flags);
2093                                 fdput(out);
2094                         }
2095                 }
2096                 fdput(in);
2097         }
2098
2099         return error;
2100 }