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        if (sd->len < sd->total_len)
 700                more |= MSG_SENDPAGE_NOTLAST;
 701        return file->f_op->sendpage(file, buf->page, buf->offset,
 702                                    sd->len, &pos, more);
 703}
 704
 705/*
 706 * This is a little more tricky than the file -> pipe splicing. There are
 707 * basically three cases:
 708 *
 709 *      - Destination page already exists in the address space and there
 710 *        are users of it. For that case we have no other option that
 711 *        copying the data. Tough luck.
 712 *      - Destination page already exists in the address space, but there
 713 *        are no users of it. Make sure it's uptodate, then drop it. Fall
 714 *        through to last case.
 715 *      - Destination page does not exist, we can add the pipe page to
 716 *        the page cache and avoid the copy.
 717 *
 718 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 719 * sd->flags), we attempt to migrate pages from the pipe to the output
 720 * file address space page cache. This is possible if no one else has
 721 * the pipe page referenced outside of the pipe and page cache. If
 722 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 723 * a new page in the output file page cache and fill/dirty that.
 724 */
 725int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 726                 struct splice_desc *sd)
 727{
 728        struct file *file = sd->u.file;
 729        struct address_space *mapping = file->f_mapping;
 730        unsigned int offset, this_len;
 731        struct page *page;
 732        void *fsdata;
 733        int ret;
 734
 735        offset = sd->pos & ~PAGE_CACHE_MASK;
 736
 737        this_len = sd->len;
 738        if (this_len + offset > PAGE_CACHE_SIZE)
 739                this_len = PAGE_CACHE_SIZE - offset;
 740
 741        ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 742                                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 743        if (unlikely(ret))
 744                goto out;
 745
 746        if (buf->page != page) {
 747                char *src = buf->ops->map(pipe, buf, 1);
 748                char *dst = kmap_atomic(page);
 749
 750                memcpy(dst + offset, src + buf->offset, this_len);
 751                flush_dcache_page(page);
 752                kunmap_atomic(dst);
 753                buf->ops->unmap(pipe, buf, src);
 754        }
 755        ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 756                                page, fsdata);
 757out:
 758        return ret;
 759}
 760EXPORT_SYMBOL(pipe_to_file);
 761
 762static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 763{
 764        smp_mb();
 765        if (waitqueue_active(&pipe->wait))
 766                wake_up_interruptible(&pipe->wait);
 767        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 768}
 769
 770/**
 771 * splice_from_pipe_feed - feed available data from a pipe to a file
 772 * @pipe:       pipe to splice from
 773 * @sd:         information to @actor
 774 * @actor:      handler that splices the data
 775 *
 776 * Description:
 777 *    This function loops over the pipe and calls @actor to do the
 778 *    actual moving of a single struct pipe_buffer to the desired
 779 *    destination.  It returns when there's no more buffers left in
 780 *    the pipe or if the requested number of bytes (@sd->total_len)
 781 *    have been copied.  It returns a positive number (one) if the
 782 *    pipe needs to be filled with more data, zero if the required
 783 *    number of bytes have been copied and -errno on error.
 784 *
 785 *    This, together with splice_from_pipe_{begin,end,next}, may be
 786 *    used to implement the functionality of __splice_from_pipe() when
 787 *    locking is required around copying the pipe buffers to the
 788 *    destination.
 789 */
 790int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 791                          splice_actor *actor)
 792{
 793        int ret;
 794
 795        while (pipe->nrbufs) {
 796                struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 797                const struct pipe_buf_operations *ops = buf->ops;
 798
 799                sd->len = buf->len;
 800                if (sd->len > sd->total_len)
 801                        sd->len = sd->total_len;
 802
 803                ret = buf->ops->confirm(pipe, buf);
 804                if (unlikely(ret)) {
 805                        if (ret == -ENODATA)
 806                                ret = 0;
 807                        return ret;
 808                }
 809
 810                ret = actor(pipe, buf, sd);
 811                if (ret <= 0)
 812                        return ret;
 813
 814                buf->offset += ret;
 815                buf->len -= ret;
 816
 817                sd->num_spliced += ret;
 818                sd->len -= ret;
 819                sd->pos += ret;
 820                sd->total_len -= ret;
 821
 822                if (!buf->len) {
 823                        buf->ops = NULL;
 824                        ops->release(pipe, buf);
 825                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 826                        pipe->nrbufs--;
 827                        if (pipe->inode)
 828                                sd->need_wakeup = true;
 829                }
 830
 831                if (!sd->total_len)
 832                        return 0;
 833        }
 834
 835        return 1;
 836}
 837EXPORT_SYMBOL(splice_from_pipe_feed);
 838
 839/**
 840 * splice_from_pipe_next - wait for some data to splice from
 841 * @pipe:       pipe to splice from
 842 * @sd:         information about the splice operation
 843 *
 844 * Description:
 845 *    This function will wait for some data and return a positive
 846 *    value (one) if pipe buffers are available.  It will return zero
 847 *    or -errno if no more data needs to be spliced.
 848 */
 849int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 850{
 851        while (!pipe->nrbufs) {
 852                if (!pipe->writers)
 853                        return 0;
 854
 855                if (!pipe->waiting_writers && sd->num_spliced)
 856                        return 0;
 857
 858                if (sd->flags & SPLICE_F_NONBLOCK)
 859                        return -EAGAIN;
 860
 861                if (signal_pending(current))
 862                        return -ERESTARTSYS;
 863
 864                if (sd->need_wakeup) {
 865                        wakeup_pipe_writers(pipe);
 866                        sd->need_wakeup = false;
 867                }
 868
 869                pipe_wait(pipe);
 870        }
 871
 872        return 1;
 873}
 874EXPORT_SYMBOL(splice_from_pipe_next);
 875
 876/**
 877 * splice_from_pipe_begin - start splicing from pipe
 878 * @sd:         information about the splice operation
 879 *
 880 * Description:
 881 *    This function should be called before a loop containing
 882 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 883 *    initialize the necessary fields of @sd.
 884 */
 885void splice_from_pipe_begin(struct splice_desc *sd)
 886{
 887        sd->num_spliced = 0;
 888        sd->need_wakeup = false;
 889}
 890EXPORT_SYMBOL(splice_from_pipe_begin);
 891
 892/**
 893 * splice_from_pipe_end - finish splicing from pipe
 894 * @pipe:       pipe to splice from
 895 * @sd:         information about the splice operation
 896 *
 897 * Description:
 898 *    This function will wake up pipe writers if necessary.  It should
 899 *    be called after a loop containing splice_from_pipe_next() and
 900 *    splice_from_pipe_feed().
 901 */
 902void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 903{
 904        if (sd->need_wakeup)
 905                wakeup_pipe_writers(pipe);
 906}
 907EXPORT_SYMBOL(splice_from_pipe_end);
 908
 909/**
 910 * __splice_from_pipe - splice data from a pipe to given actor
 911 * @pipe:       pipe to splice from
 912 * @sd:         information to @actor
 913 * @actor:      handler that splices the data
 914 *
 915 * Description:
 916 *    This function does little more than loop over the pipe and call
 917 *    @actor to do the actual moving of a single struct pipe_buffer to
 918 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 919 *    pipe_to_user.
 920 *
 921 */
 922ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 923                           splice_actor *actor)
 924{
 925        int ret;
 926
 927        splice_from_pipe_begin(sd);
 928        do {
 929                ret = splice_from_pipe_next(pipe, sd);
 930                if (ret > 0)
 931                        ret = splice_from_pipe_feed(pipe, sd, actor);
 932        } while (ret > 0);
 933        splice_from_pipe_end(pipe, sd);
 934
 935        return sd->num_spliced ? sd->num_spliced : ret;
 936}
 937EXPORT_SYMBOL(__splice_from_pipe);
 938
 939/**
 940 * splice_from_pipe - splice data from a pipe to a file
 941 * @pipe:       pipe to splice from
 942 * @out:        file to splice to
 943 * @ppos:       position in @out
 944 * @len:        how many bytes to splice
 945 * @flags:      splice modifier flags
 946 * @actor:      handler that splices the data
 947 *
 948 * Description:
 949 *    See __splice_from_pipe. This function locks the pipe inode,
 950 *    otherwise it's identical to __splice_from_pipe().
 951 *
 952 */
 953ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 954                         loff_t *ppos, size_t len, unsigned int flags,
 955                         splice_actor *actor)
 956{
 957        ssize_t ret;
 958        struct splice_desc sd = {
 959                .total_len = len,
 960                .flags = flags,
 961                .pos = *ppos,
 962                .u.file = out,
 963        };
 964
 965        pipe_lock(pipe);
 966        ret = __splice_from_pipe(pipe, &sd, actor);
 967        pipe_unlock(pipe);
 968
 969        return ret;
 970}
 971
 972/**
 973 * generic_file_splice_write - splice data from a pipe to a file
 974 * @pipe:       pipe info
 975 * @out:        file to write to
 976 * @ppos:       position in @out
 977 * @len:        number of bytes to splice
 978 * @flags:      splice modifier flags
 979 *
 980 * Description:
 981 *    Will either move or copy pages (determined by @flags options) from
 982 *    the given pipe inode to the given file.
 983 *
 984 */
 985ssize_t
 986generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 987                          loff_t *ppos, size_t len, unsigned int flags)
 988{
 989        struct address_space *mapping = out->f_mapping;
 990        struct inode *inode = mapping->host;
 991        struct splice_desc sd = {
 992                .total_len = len,
 993                .flags = flags,
 994                .pos = *ppos,
 995                .u.file = out,
 996        };
 997        ssize_t ret;
 998
 999        pipe_lock(pipe);
1000
1001        splice_from_pipe_begin(&sd);
1002        do {
1003                ret = splice_from_pipe_next(pipe, &sd);
1004                if (ret <= 0)
1005                        break;
1006
1007                mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1008                ret = file_remove_suid(out);
1009                if (!ret) {
1010                        ret = file_update_time(out);
1011                        if (!ret)
1012                                ret = splice_from_pipe_feed(pipe, &sd,
1013                                                            pipe_to_file);
1014                }
1015                mutex_unlock(&inode->i_mutex);
1016        } while (ret > 0);
1017        splice_from_pipe_end(pipe, &sd);
1018
1019        pipe_unlock(pipe);
1020
1021        if (sd.num_spliced)
1022                ret = sd.num_spliced;
1023
1024        if (ret > 0) {
1025                unsigned long nr_pages;
1026                int err;
1027
1028                nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1029
1030                err = generic_write_sync(out, *ppos, ret);
1031                if (err)
1032                        ret = err;
1033                else
1034                        *ppos += ret;
1035                balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1036        }
1037
1038        return ret;
1039}
1040
1041EXPORT_SYMBOL(generic_file_splice_write);
1042
1043static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1044                          struct splice_desc *sd)
1045{
1046        int ret;
1047        void *data;
1048
1049        data = buf->ops->map(pipe, buf, 0);
1050        ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1051        buf->ops->unmap(pipe, buf, data);
1052
1053        return ret;
1054}
1055
1056static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1057                                         struct file *out, loff_t *ppos,
1058                                         size_t len, unsigned int flags)
1059{
1060        ssize_t ret;
1061
1062        ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1063        if (ret > 0)
1064                *ppos += ret;
1065
1066        return ret;
1067}
1068
1069/**
1070 * generic_splice_sendpage - splice data from a pipe to a socket
1071 * @pipe:       pipe to splice from
1072 * @out:        socket to write to
1073 * @ppos:       position in @out
1074 * @len:        number of bytes to splice
1075 * @flags:      splice modifier flags
1076 *
1077 * Description:
1078 *    Will send @len bytes from the pipe to a network socket. No data copying
1079 *    is involved.
1080 *
1081 */
1082ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1083                                loff_t *ppos, size_t len, unsigned int flags)
1084{
1085        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1086}
1087
1088EXPORT_SYMBOL(generic_splice_sendpage);
1089
1090/*
1091 * Attempt to initiate a splice from pipe to file.
1092 */
1093static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1094                           loff_t *ppos, size_t len, unsigned int flags)
1095{
1096        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1097                                loff_t *, size_t, unsigned int);
1098        int ret;
1099
1100        if (unlikely(!(out->f_mode & FMODE_WRITE)))
1101                return -EBADF;
1102
1103        if (unlikely(out->f_flags & O_APPEND))
1104                return -EINVAL;
1105
1106        ret = rw_verify_area(WRITE, out, ppos, len);
1107        if (unlikely(ret < 0))
1108                return ret;
1109
1110        if (out->f_op && out->f_op->splice_write)
1111                splice_write = out->f_op->splice_write;
1112        else
1113                splice_write = default_file_splice_write;
1114
1115        return splice_write(pipe, out, ppos, len, flags);
1116}
1117
1118/*
1119 * Attempt to initiate a splice from a file to a pipe.
1120 */
1121static long do_splice_to(struct file *in, loff_t *ppos,
1122                         struct pipe_inode_info *pipe, size_t len,
1123                         unsigned int flags)
1124{
1125        ssize_t (*splice_read)(struct file *, loff_t *,
1126                               struct pipe_inode_info *, size_t, unsigned int);
1127        int ret;
1128
1129        if (unlikely(!(in->f_mode & FMODE_READ)))
1130                return -EBADF;
1131
1132        ret = rw_verify_area(READ, in, ppos, len);
1133        if (unlikely(ret < 0))
1134                return ret;
1135
1136        if (in->f_op && in->f_op->splice_read)
1137                splice_read = in->f_op->splice_read;
1138        else
1139                splice_read = default_file_splice_read;
1140
1141        return splice_read(in, ppos, pipe, len, flags);
1142}
1143
1144/**
1145 * splice_direct_to_actor - splices data directly between two non-pipes
1146 * @in:         file to splice from
1147 * @sd:         actor information on where to splice to
1148 * @actor:      handles the data splicing
1149 *
1150 * Description:
1151 *    This is a special case helper to splice directly between two
1152 *    points, without requiring an explicit pipe. Internally an allocated
1153 *    pipe is cached in the process, and reused during the lifetime of
1154 *    that process.
1155 *
1156 */
1157ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1158                               splice_direct_actor *actor)
1159{
1160        struct pipe_inode_info *pipe;
1161        long ret, bytes;
1162        umode_t i_mode;
1163        size_t len;
1164        int i, flags;
1165
1166        /*
1167         * We require the input being a regular file, as we don't want to
1168         * randomly drop data for eg socket -> socket splicing. Use the
1169         * piped splicing for that!
1170         */
1171        i_mode = in->f_path.dentry->d_inode->i_mode;
1172        if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1173                return -EINVAL;
1174
1175        /*
1176         * neither in nor out is a pipe, setup an internal pipe attached to
1177         * 'out' and transfer the wanted data from 'in' to 'out' through that
1178         */
1179        pipe = current->splice_pipe;
1180        if (unlikely(!pipe)) {
1181                pipe = alloc_pipe_info(NULL);
1182                if (!pipe)
1183                        return -ENOMEM;
1184
1185                /*
1186                 * We don't have an immediate reader, but we'll read the stuff
1187                 * out of the pipe right after the splice_to_pipe(). So set
1188                 * PIPE_READERS appropriately.
1189                 */
1190                pipe->readers = 1;
1191
1192                current->splice_pipe = pipe;
1193        }
1194
1195        /*
1196         * Do the splice.
1197         */
1198        ret = 0;
1199        bytes = 0;
1200        len = sd->total_len;
1201        flags = sd->flags;
1202
1203        /*
1204         * Don't block on output, we have to drain the direct pipe.
1205         */
1206        sd->flags &= ~SPLICE_F_NONBLOCK;
1207
1208        while (len) {
1209                size_t read_len;
1210                loff_t pos = sd->pos, prev_pos = pos;
1211
1212                ret = do_splice_to(in, &pos, pipe, len, flags);
1213                if (unlikely(ret <= 0))
1214                        goto out_release;
1215
1216                read_len = ret;
1217                sd->total_len = read_len;
1218
1219                /*
1220                 * NOTE: nonblocking mode only applies to the input. We
1221                 * must not do the output in nonblocking mode as then we
1222                 * could get stuck data in the internal pipe:
1223                 */
1224                ret = actor(pipe, sd);
1225                if (unlikely(ret <= 0)) {
1226                        sd->pos = prev_pos;
1227                        goto out_release;
1228                }
1229
1230                bytes += ret;
1231                len -= ret;
1232                sd->pos = pos;
1233
1234                if (ret < read_len) {
1235                        sd->pos = prev_pos + ret;
1236                        goto out_release;
1237                }
1238        }
1239
1240done:
1241        pipe->nrbufs = pipe->curbuf = 0;
1242        file_accessed(in);
1243        return bytes;
1244
1245out_release:
1246        /*
1247         * If we did an incomplete transfer we must release
1248         * the pipe buffers in question:
1249         */
1250        for (i = 0; i < pipe->buffers; i++) {
1251                struct pipe_buffer *buf = pipe->bufs + i;
1252
1253                if (buf->ops) {
1254                        buf->ops->release(pipe, buf);
1255                        buf->ops = NULL;
1256                }
1257        }
1258
1259        if (!bytes)
1260                bytes = ret;
1261
1262        goto done;
1263}
1264EXPORT_SYMBOL(splice_direct_to_actor);
1265
1266static int direct_splice_actor(struct pipe_inode_info *pipe,
1267                               struct splice_desc *sd)
1268{
1269        struct file *file = sd->u.file;
1270
1271        return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1272                              sd->flags);
1273}
1274
1275/**
1276 * do_splice_direct - splices data directly between two files
1277 * @in:         file to splice from
1278 * @ppos:       input file offset
1279 * @out:        file to splice to
1280 * @len:        number of bytes to splice
1281 * @flags:      splice modifier flags
1282 *
1283 * Description:
1284 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1285 *    doing it in the application would incur an extra system call
1286 *    (splice in + splice out, as compared to just sendfile()). So this helper
1287 *    can splice directly through a process-private pipe.
1288 *
1289 */
1290long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1291                      size_t len, unsigned int flags)
1292{
1293        struct splice_desc sd = {
1294                .len            = len,
1295                .total_len      = len,
1296                .flags          = flags,
1297                .pos            = *ppos,
1298                .u.file         = out,
1299        };
1300        long ret;
1301
1302        ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1303        if (ret > 0)
1304                *ppos = sd.pos;
1305
1306        return ret;
1307}
1308
1309static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1310                               struct pipe_inode_info *opipe,
1311                               size_t len, unsigned int flags);
1312
1313/*
1314 * Determine where to splice to/from.
1315 */
1316static long do_splice(struct file *in, loff_t __user *off_in,
1317                      struct file *out, loff_t __user *off_out,
1318                      size_t len, unsigned int flags)
1319{
1320        struct pipe_inode_info *ipipe;
1321        struct pipe_inode_info *opipe;
1322        loff_t offset, *off;
1323        long ret;
1324
1325        ipipe = get_pipe_info(in);
1326        opipe = get_pipe_info(out);
1327
1328        if (ipipe && opipe) {
1329                if (off_in || off_out)
1330                        return -ESPIPE;
1331
1332                if (!(in->f_mode & FMODE_READ))
1333                        return -EBADF;
1334
1335                if (!(out->f_mode & FMODE_WRITE))
1336                        return -EBADF;
1337
1338                /* Splicing to self would be fun, but... */
1339                if (ipipe == opipe)
1340                        return -EINVAL;
1341
1342                return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1343        }
1344
1345        if (ipipe) {
1346                if (off_in)
1347                        return -ESPIPE;
1348                if (off_out) {
1349                        if (!(out->f_mode & FMODE_PWRITE))
1350                                return -EINVAL;
1351                        if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1352                                return -EFAULT;
1353                        off = &offset;
1354                } else
1355                        off = &out->f_pos;
1356
1357                ret = do_splice_from(ipipe, out, off, len, flags);
1358
1359                if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1360                        ret = -EFAULT;
1361
1362                return ret;
1363        }
1364
1365        if (opipe) {
1366                if (off_out)
1367                        return -ESPIPE;
1368                if (off_in) {
1369                        if (!(in->f_mode & FMODE_PREAD))
1370                                return -EINVAL;
1371                        if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1372                                return -EFAULT;
1373                        off = &offset;
1374                } else
1375                        off = &in->f_pos;
1376
1377                ret = do_splice_to(in, off, opipe, len, flags);
1378
1379                if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1380                        ret = -EFAULT;
1381
1382                return ret;
1383        }
1384
1385        return -EINVAL;
1386}
1387
1388/*
1389 * Map an iov into an array of pages and offset/length tupples. With the
1390 * partial_page structure, we can map several non-contiguous ranges into
1391 * our ones pages[] map instead of splitting that operation into pieces.
1392 * Could easily be exported as a generic helper for other users, in which
1393 * case one would probably want to add a 'max_nr_pages' parameter as well.
1394 */
1395static int get_iovec_page_array(const struct iovec __user *iov,
1396                                unsigned int nr_vecs, struct page **pages,
1397                                struct partial_page *partial, bool aligned,
1398                                unsigned int pipe_buffers)
1399{
1400        int buffers = 0, error = 0;
1401
1402        while (nr_vecs) {
1403                unsigned long off, npages;
1404                struct iovec entry;
1405                void __user *base;
1406                size_t len;
1407                int i;
1408
1409                error = -EFAULT;
1410                if (copy_from_user(&entry, iov, sizeof(entry)))
1411                        break;
1412
1413                base = entry.iov_base;
1414                len = entry.iov_len;
1415
1416                /*
1417                 * Sanity check this iovec. 0 read succeeds.
1418                 */
1419                error = 0;
1420                if (unlikely(!len))
1421                        break;
1422                error = -EFAULT;
1423                if (!access_ok(VERIFY_READ, base, len))
1424                        break;
1425
1426                /*
1427                 * Get this base offset and number of pages, then map
1428                 * in the user pages.
1429                 */
1430                off = (unsigned long) base & ~PAGE_MASK;
1431
1432                /*
1433                 * If asked for alignment, the offset must be zero and the
1434                 * length a multiple of the PAGE_SIZE.
1435                 */
1436                error = -EINVAL;
1437                if (aligned && (off || len & ~PAGE_MASK))
1438                        break;
1439
1440                npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1441                if (npages > pipe_buffers - buffers)
1442                        npages = pipe_buffers - buffers;
1443
1444                error = get_user_pages_fast((unsigned long)base, npages,
1445                                        0, &pages[buffers]);
1446
1447                if (unlikely(error <= 0))
1448                        break;
1449
1450                /*
1451                 * Fill this contiguous range into the partial page map.
1452                 */
1453                for (i = 0; i < error; i++) {
1454                        const int plen = min_t(size_t, len, PAGE_SIZE - off);
1455
1456                        partial[buffers].offset = off;
1457                        partial[buffers].len = plen;
1458
1459                        off = 0;
1460                        len -= plen;
1461                        buffers++;
1462                }
1463
1464                /*
1465                 * We didn't complete this iov, stop here since it probably
1466                 * means we have to move some of this into a pipe to
1467                 * be able to continue.
1468                 */
1469                if (len)
1470                        break;
1471
1472                /*
1473                 * Don't continue if we mapped fewer pages than we asked for,
1474                 * or if we mapped the max number of pages that we have
1475                 * room for.
1476                 */
1477                if (error < npages || buffers == pipe_buffers)
1478                        break;
1479
1480                nr_vecs--;
1481                iov++;
1482        }
1483
1484        if (buffers)
1485                return buffers;
1486
1487        return error;
1488}
1489
1490static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1491                        struct splice_desc *sd)
1492{
1493        char *src;
1494        int ret;
1495
1496        /*
1497         * See if we can use the atomic maps, by prefaulting in the
1498         * pages and doing an atomic copy
1499         */
1500        if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1501                src = buf->ops->map(pipe, buf, 1);
1502                ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1503                                                        sd->len);
1504                buf->ops->unmap(pipe, buf, src);
1505                if (!ret) {
1506                        ret = sd->len;
1507                        goto out;
1508                }
1509        }
1510
1511        /*
1512         * No dice, use slow non-atomic map and copy
1513         */
1514        src = buf->ops->map(pipe, buf, 0);
1515
1516        ret = sd->len;
1517        if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1518                ret = -EFAULT;
1519
1520        buf->ops->unmap(pipe, buf, src);
1521out:
1522        if (ret > 0)
1523                sd->u.userptr += ret;
1524        return ret;
1525}
1526
1527/*
1528 * For lack of a better implementation, implement vmsplice() to userspace
1529 * as a simple copy of the pipes pages to the user iov.
1530 */
1531static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1532                             unsigned long nr_segs, unsigned int flags)
1533{
1534        struct pipe_inode_info *pipe;
1535        struct splice_desc sd;
1536        ssize_t size;
1537        int error;
1538        long ret;
1539
1540        pipe = get_pipe_info(file);
1541        if (!pipe)
1542                return -EBADF;
1543
1544        pipe_lock(pipe);
1545
1546        error = ret = 0;
1547        while (nr_segs) {
1548                void __user *base;
1549                size_t len;
1550
1551                /*
1552                 * Get user address base and length for this iovec.
1553                 */
1554                error = get_user(base, &iov->iov_base);
1555                if (unlikely(error))
1556                        break;
1557                error = get_user(len, &iov->iov_len);
1558                if (unlikely(error))
1559                        break;
1560
1561                /*
1562                 * Sanity check this iovec. 0 read succeeds.
1563                 */
1564                if (unlikely(!len))
1565                        break;
1566                if (unlikely(!base)) {
1567                        error = -EFAULT;
1568                        break;
1569                }
1570
1571                if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1572                        error = -EFAULT;
1573                        break;
1574                }
1575
1576                sd.len = 0;
1577                sd.total_len = len;
1578                sd.flags = flags;
1579                sd.u.userptr = base;
1580                sd.pos = 0;
1581
1582                size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1583                if (size < 0) {
1584                        if (!ret)
1585                                ret = size;
1586
1587                        break;
1588                }
1589
1590                ret += size;
1591
1592                if (size < len)
1593                        break;
1594
1595                nr_segs--;
1596                iov++;
1597        }
1598
1599        pipe_unlock(pipe);
1600
1601        if (!ret)
1602                ret = error;
1603
1604        return ret;
1605}
1606
1607/*
1608 * vmsplice splices a user address range into a pipe. It can be thought of
1609 * as splice-from-memory, where the regular splice is splice-from-file (or
1610 * to file). In both cases the output is a pipe, naturally.
1611 */
1612static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1613                             unsigned long nr_segs, unsigned int flags)
1614{
1615        struct pipe_inode_info *pipe;
1616        struct page *pages[PIPE_DEF_BUFFERS];
1617        struct partial_page partial[PIPE_DEF_BUFFERS];
1618        struct splice_pipe_desc spd = {
1619                .pages = pages,
1620                .partial = partial,
1621                .nr_pages_max = PIPE_DEF_BUFFERS,
1622                .flags = flags,
1623                .ops = &user_page_pipe_buf_ops,
1624                .spd_release = spd_release_page,
1625        };
1626        long ret;
1627
1628        pipe = get_pipe_info(file);
1629        if (!pipe)
1630                return -EBADF;
1631
1632        if (splice_grow_spd(pipe, &spd))
1633                return -ENOMEM;
1634
1635        spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1636                                            spd.partial, false,
1637                                            spd.nr_pages_max);
1638        if (spd.nr_pages <= 0)
1639                ret = spd.nr_pages;
1640        else
1641                ret = splice_to_pipe(pipe, &spd);
1642
1643        splice_shrink_spd(&spd);
1644        return ret;
1645}
1646
1647/*
1648 * Note that vmsplice only really supports true splicing _from_ user memory
1649 * to a pipe, not the other way around. Splicing from user memory is a simple
1650 * operation that can be supported without any funky alignment restrictions
1651 * or nasty vm tricks. We simply map in the user memory and fill them into
1652 * a pipe. The reverse isn't quite as easy, though. There are two possible
1653 * solutions for that:
1654 *
1655 *      - memcpy() the data internally, at which point we might as well just
1656 *        do a regular read() on the buffer anyway.
1657 *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1658 *        has restriction limitations on both ends of the pipe).
1659 *
1660 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1661 *
1662 */
1663SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1664                unsigned long, nr_segs, unsigned int, flags)
1665{
1666        struct file *file;
1667        long error;
1668        int fput;
1669
1670        if (unlikely(nr_segs > UIO_MAXIOV))
1671                return -EINVAL;
1672        else if (unlikely(!nr_segs))
1673                return 0;
1674
1675        error = -EBADF;
1676        file = fget_light(fd, &fput);
1677        if (file) {
1678                if (file->f_mode & FMODE_WRITE)
1679                        error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1680                else if (file->f_mode & FMODE_READ)
1681                        error = vmsplice_to_user(file, iov, nr_segs, flags);
1682
1683                fput_light(file, fput);
1684        }
1685
1686        return error;
1687}
1688
1689SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1690                int, fd_out, loff_t __user *, off_out,
1691                size_t, len, unsigned int, flags)
1692{
1693        long error;
1694        struct file *in, *out;
1695        int fput_in, fput_out;
1696
1697        if (unlikely(!len))
1698                return 0;
1699
1700        error = -EBADF;
1701        in = fget_light(fd_in, &fput_in);
1702        if (in) {
1703                if (in->f_mode & FMODE_READ) {
1704                        out = fget_light(fd_out, &fput_out);
1705                        if (out) {
1706                                if (out->f_mode & FMODE_WRITE)
1707                                        error = do_splice(in, off_in,
1708                                                          out, off_out,
1709                                                          len, flags);
1710                                fput_light(out, fput_out);
1711                        }
1712                }
1713
1714                fput_light(in, fput_in);
1715        }
1716
1717        return error;
1718}
1719
1720/*
1721 * Make sure there's data to read. Wait for input if we can, otherwise
1722 * return an appropriate error.
1723 */
1724static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1725{
1726        int ret;
1727
1728        /*
1729         * Check ->nrbufs without the inode lock first. This function
1730         * is speculative anyways, so missing one is ok.
1731         */
1732        if (pipe->nrbufs)
1733                return 0;
1734
1735        ret = 0;
1736        pipe_lock(pipe);
1737
1738        while (!pipe->nrbufs) {
1739                if (signal_pending(current)) {
1740                        ret = -ERESTARTSYS;
1741                        break;
1742                }
1743                if (!pipe->writers)
1744                        break;
1745                if (!pipe->waiting_writers) {
1746                        if (flags & SPLICE_F_NONBLOCK) {
1747                                ret = -EAGAIN;
1748                                break;
1749                        }
1750                }
1751                pipe_wait(pipe);
1752        }
1753
1754        pipe_unlock(pipe);
1755        return ret;
1756}
1757
1758/*
1759 * Make sure there's writeable room. Wait for room if we can, otherwise
1760 * return an appropriate error.
1761 */
1762static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1763{
1764        int ret;
1765
1766        /*
1767         * Check ->nrbufs without the inode lock first. This function
1768         * is speculative anyways, so missing one is ok.
1769         */
1770        if (pipe->nrbufs < pipe->buffers)
1771                return 0;
1772
1773        ret = 0;
1774        pipe_lock(pipe);
1775
1776        while (pipe->nrbufs >= pipe->buffers) {
1777                if (!pipe->readers) {
1778                        send_sig(SIGPIPE, current, 0);
1779                        ret = -EPIPE;
1780                        break;
1781                }
1782                if (flags & SPLICE_F_NONBLOCK) {
1783                        ret = -EAGAIN;
1784                        break;
1785                }
1786                if (signal_pending(current)) {
1787                        ret = -ERESTARTSYS;
1788                        break;
1789                }
1790                pipe->waiting_writers++;
1791                pipe_wait(pipe);
1792                pipe->waiting_writers--;
1793        }
1794
1795        pipe_unlock(pipe);
1796        return ret;
1797}
1798
1799/*
1800 * Splice contents of ipipe to opipe.
1801 */
1802static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1803                               struct pipe_inode_info *opipe,
1804                               size_t len, unsigned int flags)
1805{
1806        struct pipe_buffer *ibuf, *obuf;
1807        int ret = 0, nbuf;
1808        bool input_wakeup = false;
1809
1810
1811retry:
1812        ret = ipipe_prep(ipipe, flags);
1813        if (ret)
1814                return ret;
1815
1816        ret = opipe_prep(opipe, flags);
1817        if (ret)
1818                return ret;
1819
1820        /*
1821         * Potential ABBA deadlock, work around it by ordering lock
1822         * grabbing by pipe info address. Otherwise two different processes
1823         * could deadlock (one doing tee from A -> B, the other from B -> A).
1824         */
1825        pipe_double_lock(ipipe, opipe);
1826
1827        do {
1828                if (!opipe->readers) {
1829                        send_sig(SIGPIPE, current, 0);
1830                        if (!ret)
1831                                ret = -EPIPE;
1832                        break;
1833                }
1834
1835                if (!ipipe->nrbufs && !ipipe->writers)
1836                        break;
1837
1838                /*
1839                 * Cannot make any progress, because either the input
1840                 * pipe is empty or the output pipe is full.
1841                 */
1842                if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1843                        /* Already processed some buffers, break */
1844                        if (ret)
1845                                break;
1846
1847                        if (flags & SPLICE_F_NONBLOCK) {
1848                                ret = -EAGAIN;
1849                                break;
1850                        }
1851
1852                        /*
1853                         * We raced with another reader/writer and haven't
1854                         * managed to process any buffers.  A zero return
1855                         * value means EOF, so retry instead.
1856                         */
1857                        pipe_unlock(ipipe);
1858                        pipe_unlock(opipe);
1859                        goto retry;
1860                }
1861
1862                ibuf = ipipe->bufs + ipipe->curbuf;
1863                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1864                obuf = opipe->bufs + nbuf;
1865
1866                if (len >= ibuf->len) {
1867                        /*
1868                         * Simply move the whole buffer from ipipe to opipe
1869                         */
1870                        *obuf = *ibuf;
1871                        ibuf->ops = NULL;
1872                        opipe->nrbufs++;
1873                        ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1874                        ipipe->nrbufs--;
1875                        input_wakeup = true;
1876                } else {
1877                        /*
1878                         * Get a reference to this pipe buffer,
1879                         * so we can copy the contents over.
1880                         */
1881                        ibuf->ops->get(ipipe, ibuf);
1882                        *obuf = *ibuf;
1883
1884                        /*
1885                         * Don't inherit the gift flag, we need to
1886                         * prevent multiple steals of this page.
1887                         */
1888                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1889
1890                        obuf->len = len;
1891                        opipe->nrbufs++;
1892                        ibuf->offset += obuf->len;
1893                        ibuf->len -= obuf->len;
1894                }
1895                ret += obuf->len;
1896                len -= obuf->len;
1897        } while (len);
1898
1899        pipe_unlock(ipipe);
1900        pipe_unlock(opipe);
1901
1902        /*
1903         * If we put data in the output pipe, wakeup any potential readers.
1904         */
1905        if (ret > 0)
1906                wakeup_pipe_readers(opipe);
1907
1908        if (input_wakeup)
1909                wakeup_pipe_writers(ipipe);
1910
1911        return ret;
1912}
1913
1914/*
1915 * Link contents of ipipe to opipe.
1916 */
1917static int link_pipe(struct pipe_inode_info *ipipe,
1918                     struct pipe_inode_info *opipe,
1919                     size_t len, unsigned int flags)
1920{
1921        struct pipe_buffer *ibuf, *obuf;
1922        int ret = 0, i = 0, nbuf;
1923
1924        /*
1925         * Potential ABBA deadlock, work around it by ordering lock
1926         * grabbing by pipe info address. Otherwise two different processes
1927         * could deadlock (one doing tee from A -> B, the other from B -> A).
1928         */
1929        pipe_double_lock(ipipe, opipe);
1930
1931        do {
1932                if (!opipe->readers) {
1933                        send_sig(SIGPIPE, current, 0);
1934                        if (!ret)
1935                                ret = -EPIPE;
1936                        break;
1937                }
1938
1939                /*
1940                 * If we have iterated all input buffers or ran out of
1941                 * output room, break.
1942                 */
1943                if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1944                        break;
1945
1946                ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1947                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1948
1949                /*
1950                 * Get a reference to this pipe buffer,
1951                 * so we can copy the contents over.
1952                 */
1953                ibuf->ops->get(ipipe, ibuf);
1954
1955                obuf = opipe->bufs + nbuf;
1956                *obuf = *ibuf;
1957
1958                /*
1959                 * Don't inherit the gift flag, we need to
1960                 * prevent multiple steals of this page.
1961                 */
1962                obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1963
1964                if (obuf->len > len)
1965                        obuf->len = len;
1966
1967                opipe->nrbufs++;
1968                ret += obuf->len;
1969                len -= obuf->len;
1970                i++;
1971        } while (len);
1972
1973        /*
1974         * return EAGAIN if we have the potential of some data in the
1975         * future, otherwise just return 0
1976         */
1977        if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1978                ret = -EAGAIN;
1979
1980        pipe_unlock(ipipe);
1981        pipe_unlock(opipe);
1982
1983        /*
1984         * If we put data in the output pipe, wakeup any potential readers.
1985         */
1986        if (ret > 0)
1987                wakeup_pipe_readers(opipe);
1988
1989        return ret;
1990}
1991
1992/*
1993 * This is a tee(1) implementation that works on pipes. It doesn't copy
1994 * any data, it simply references the 'in' pages on the 'out' pipe.
1995 * The 'flags' used are the SPLICE_F_* variants, currently the only
1996 * applicable one is SPLICE_F_NONBLOCK.
1997 */
1998static long do_tee(struct file *in, struct file *out, size_t len,
1999                   unsigned int flags)
2000{
2001        struct pipe_inode_info *ipipe = get_pipe_info(in);
2002        struct pipe_inode_info *opipe = get_pipe_info(out);
2003        int ret = -EINVAL;
2004
2005        /*
2006         * Duplicate the contents of ipipe to opipe without actually
2007         * copying the data.
2008         */
2009        if (ipipe && opipe && ipipe != opipe) {
2010                /*
2011                 * Keep going, unless we encounter an error. The ipipe/opipe
2012                 * ordering doesn't really matter.
2013                 */
2014                ret = ipipe_prep(ipipe, flags);
2015                if (!ret) {
2016                        ret = opipe_prep(opipe, flags);
2017                        if (!ret)
2018                                ret = link_pipe(ipipe, opipe, len, flags);
2019                }
2020        }
2021
2022        return ret;
2023}
2024
2025SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2026{
2027        struct file *in;
2028        int error, fput_in;
2029
2030        if (unlikely(!len))
2031                return 0;
2032
2033        error = -EBADF;
2034        in = fget_light(fdin, &fput_in);
2035        if (in) {
2036                if (in->f_mode & FMODE_READ) {
2037                        int fput_out;
2038                        struct file *out = fget_light(fdout, &fput_out);
2039
2040                        if (out) {
2041                                if (out->f_mode & FMODE_WRITE)
2042                                        error = do_tee(in, out, len, flags);
2043                                fput_light(out, fput_out);
2044                        }
2045                }
2046                fput_light(in, fput_in);
2047        }
2048
2049        return error;
2050}
2051
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