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