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