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