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