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/buffer_head.h>
  29#include <linux/module.h>
  30#include <linux/syscalls.h>
  31#include <linux/uio.h>
  32#include <linux/security.h>
  33#include <linux/gfp.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(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 277{
 278        if (pipe->buffers <= PIPE_DEF_BUFFERS)
 279                return 0;
 280
 281        spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
 282        spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
 283
 284        if (spd->pages && spd->partial)
 285                return 0;
 286
 287        kfree(spd->pages);
 288        kfree(spd->partial);
 289        return -ENOMEM;
 290}
 291
 292void splice_shrink_spd(struct pipe_inode_info *pipe,
 293                       struct splice_pipe_desc *spd)
 294{
 295        if (pipe->buffers <= PIPE_DEF_BUFFERS)
 296                return;
 297
 298        kfree(spd->pages);
 299        kfree(spd->partial);
 300}
 301
 302static int
 303__generic_file_splice_read(struct file *in, loff_t *ppos,
 304                           struct pipe_inode_info *pipe, size_t len,
 305                           unsigned int flags)
 306{
 307        struct address_space *mapping = in->f_mapping;
 308        unsigned int loff, nr_pages, req_pages;
 309        struct page *pages[PIPE_DEF_BUFFERS];
 310        struct partial_page partial[PIPE_DEF_BUFFERS];
 311        struct page *page;
 312        pgoff_t index, end_index;
 313        loff_t isize;
 314        int error, page_nr;
 315        struct splice_pipe_desc spd = {
 316                .pages = pages,
 317                .partial = partial,
 318                .flags = flags,
 319                .ops = &page_cache_pipe_buf_ops,
 320                .spd_release = spd_release_page,
 321        };
 322
 323        if (splice_grow_spd(pipe, &spd))
 324                return -ENOMEM;
 325
 326        index = *ppos >> PAGE_CACHE_SHIFT;
 327        loff = *ppos & ~PAGE_CACHE_MASK;
 328        req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 329        nr_pages = min(req_pages, pipe->buffers);
 330
 331        /*
 332         * Lookup the (hopefully) full range of pages we need.
 333         */
 334        spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
 335        index += spd.nr_pages;
 336
 337        /*
 338         * If find_get_pages_contig() returned fewer pages than we needed,
 339         * readahead/allocate the rest and fill in the holes.
 340         */
 341        if (spd.nr_pages < nr_pages)
 342                page_cache_sync_readahead(mapping, &in->f_ra, in,
 343                                index, req_pages - spd.nr_pages);
 344
 345        error = 0;
 346        while (spd.nr_pages < nr_pages) {
 347                /*
 348                 * Page could be there, find_get_pages_contig() breaks on
 349                 * the first hole.
 350                 */
 351                page = find_get_page(mapping, index);
 352                if (!page) {
 353                        /*
 354                         * page didn't exist, allocate one.
 355                         */
 356                        page = page_cache_alloc_cold(mapping);
 357                        if (!page)
 358                                break;
 359
 360                        error = add_to_page_cache_lru(page, mapping, index,
 361                                                GFP_KERNEL);
 362                        if (unlikely(error)) {
 363                                page_cache_release(page);
 364                                if (error == -EEXIST)
 365                                        continue;
 366                                break;
 367                        }
 368                        /*
 369                         * add_to_page_cache() locks the page, unlock it
 370                         * to avoid convoluting the logic below even more.
 371                         */
 372                        unlock_page(page);
 373                }
 374
 375                spd.pages[spd.nr_pages++] = page;
 376                index++;
 377        }
 378
 379        /*
 380         * Now loop over the map and see if we need to start IO on any
 381         * pages, fill in the partial map, etc.
 382         */
 383        index = *ppos >> PAGE_CACHE_SHIFT;
 384        nr_pages = spd.nr_pages;
 385        spd.nr_pages = 0;
 386        for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 387                unsigned int this_len;
 388
 389                if (!len)
 390                        break;
 391
 392                /*
 393                 * this_len is the max we'll use from this page
 394                 */
 395                this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 396                page = spd.pages[page_nr];
 397
 398                if (PageReadahead(page))
 399                        page_cache_async_readahead(mapping, &in->f_ra, in,
 400                                        page, index, req_pages - page_nr);
 401
 402                /*
 403                 * If the page isn't uptodate, we may need to start io on it
 404                 */
 405                if (!PageUptodate(page)) {
 406                        lock_page(page);
 407
 408                        /*
 409                         * Page was truncated, or invalidated by the
 410                         * filesystem.  Redo the find/create, but this time the
 411                         * page is kept locked, so there's no chance of another
 412                         * race with truncate/invalidate.
 413                         */
 414                        if (!page->mapping) {
 415                                unlock_page(page);
 416                                page = find_or_create_page(mapping, index,
 417                                                mapping_gfp_mask(mapping));
 418
 419                                if (!page) {
 420                                        error = -ENOMEM;
 421                                        break;
 422                                }
 423                                page_cache_release(spd.pages[page_nr]);
 424                                spd.pages[page_nr] = page;
 425                        }
 426                        /*
 427                         * page was already under io and is now done, great
 428                         */
 429                        if (PageUptodate(page)) {
 430                                unlock_page(page);
 431                                goto fill_it;
 432                        }
 433
 434                        /*
 435                         * need to read in the page
 436                         */
 437                        error = mapping->a_ops->readpage(in, page);
 438                        if (unlikely(error)) {
 439                                /*
 440                                 * We really should re-lookup the page here,
 441                                 * but it complicates things a lot. Instead
 442                                 * lets just do what we already stored, and
 443                                 * we'll get it the next time we are called.
 444                                 */
 445                                if (error == AOP_TRUNCATED_PAGE)
 446                                        error = 0;
 447
 448                                break;
 449                        }
 450                }
 451fill_it:
 452                /*
 453                 * i_size must be checked after PageUptodate.
 454                 */
 455                isize = i_size_read(mapping->host);
 456                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 457                if (unlikely(!isize || index > end_index))
 458                        break;
 459
 460                /*
 461                 * if this is the last page, see if we need to shrink
 462                 * the length and stop
 463                 */
 464                if (end_index == index) {
 465                        unsigned int plen;
 466
 467                        /*
 468                         * max good bytes in this page
 469                         */
 470                        plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 471                        if (plen <= loff)
 472                                break;
 473
 474                        /*
 475                         * force quit after adding this page
 476                         */
 477                        this_len = min(this_len, plen - loff);
 478                        len = this_len;
 479                }
 480
 481                spd.partial[page_nr].offset = loff;
 482                spd.partial[page_nr].len = this_len;
 483                len -= this_len;
 484                loff = 0;
 485                spd.nr_pages++;
 486                index++;
 487        }
 488
 489        /*
 490         * Release any pages at the end, if we quit early. 'page_nr' is how far
 491         * we got, 'nr_pages' is how many pages are in the map.
 492         */
 493        while (page_nr < nr_pages)
 494                page_cache_release(spd.pages[page_nr++]);
 495        in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 496
 497        if (spd.nr_pages)
 498                error = splice_to_pipe(pipe, &spd);
 499
 500        splice_shrink_spd(pipe, &spd);
 501        return error;
 502}
 503
 504/**
 505 * generic_file_splice_read - splice data from file to a pipe
 506 * @in:         file to splice from
 507 * @ppos:       position in @in
 508 * @pipe:       pipe to splice to
 509 * @len:        number of bytes to splice
 510 * @flags:      splice modifier flags
 511 *
 512 * Description:
 513 *    Will read pages from given file and fill them into a pipe. Can be
 514 *    used as long as the address_space operations for the source implements
 515 *    a readpage() hook.
 516 *
 517 */
 518ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 519                                 struct pipe_inode_info *pipe, size_t len,
 520                                 unsigned int flags)
 521{
 522        loff_t isize, left;
 523        int ret;
 524
 525        isize = i_size_read(in->f_mapping->host);
 526        if (unlikely(*ppos >= isize))
 527                return 0;
 528
 529        left = isize - *ppos;
 530        if (unlikely(left < len))
 531                len = left;
 532
 533        ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 534        if (ret > 0) {
 535                *ppos += ret;
 536                file_accessed(in);
 537        }
 538
 539        return ret;
 540}
 541EXPORT_SYMBOL(generic_file_splice_read);
 542
 543static const struct pipe_buf_operations default_pipe_buf_ops = {
 544        .can_merge = 0,
 545        .map = generic_pipe_buf_map,
 546        .unmap = generic_pipe_buf_unmap,
 547        .confirm = generic_pipe_buf_confirm,
 548        .release = generic_pipe_buf_release,
 549        .steal = generic_pipe_buf_steal,
 550        .get = generic_pipe_buf_get,
 551};
 552
 553static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 554                            unsigned long vlen, loff_t offset)
 555{
 556        mm_segment_t old_fs;
 557        loff_t pos = offset;
 558        ssize_t res;
 559
 560        old_fs = get_fs();
 561        set_fs(get_ds());
 562        /* The cast to a user pointer is valid due to the set_fs() */
 563        res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 564        set_fs(old_fs);
 565
 566        return res;
 567}
 568
 569static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 570                            loff_t pos)
 571{
 572        mm_segment_t old_fs;
 573        ssize_t res;
 574
 575        old_fs = get_fs();
 576        set_fs(get_ds());
 577        /* The cast to a user pointer is valid due to the set_fs() */
 578        res = vfs_write(file, (const char __user *)buf, count, &pos);
 579        set_fs(old_fs);
 580
 581        return res;
 582}
 583
 584ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 585                                 struct pipe_inode_info *pipe, size_t len,
 586                                 unsigned int flags)
 587{
 588        unsigned int nr_pages;
 589        unsigned int nr_freed;
 590        size_t offset;
 591        struct page *pages[PIPE_DEF_BUFFERS];
 592        struct partial_page partial[PIPE_DEF_BUFFERS];
 593        struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 594        ssize_t res;
 595        size_t this_len;
 596        int error;
 597        int i;
 598        struct splice_pipe_desc spd = {
 599                .pages = pages,
 600                .partial = partial,
 601                .flags = flags,
 602                .ops = &default_pipe_buf_ops,
 603                .spd_release = spd_release_page,
 604        };
 605
 606        if (splice_grow_spd(pipe, &spd))
 607                return -ENOMEM;
 608
 609        res = -ENOMEM;
 610        vec = __vec;
 611        if (pipe->buffers > PIPE_DEF_BUFFERS) {
 612                vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
 613                if (!vec)
 614                        goto shrink_ret;
 615        }
 616
 617        offset = *ppos & ~PAGE_CACHE_MASK;
 618        nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 619
 620        for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
 621                struct page *page;
 622
 623                page = alloc_page(GFP_USER);
 624                error = -ENOMEM;
 625                if (!page)
 626                        goto err;
 627
 628                this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 629                vec[i].iov_base = (void __user *) page_address(page);
 630                vec[i].iov_len = this_len;
 631                spd.pages[i] = page;
 632                spd.nr_pages++;
 633                len -= this_len;
 634                offset = 0;
 635        }
 636
 637        res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 638        if (res < 0) {
 639                error = res;
 640                goto err;
 641        }
 642
 643        error = 0;
 644        if (!res)
 645                goto err;
 646
 647        nr_freed = 0;
 648        for (i = 0; i < spd.nr_pages; i++) {
 649                this_len = min_t(size_t, vec[i].iov_len, res);
 650                spd.partial[i].offset = 0;
 651                spd.partial[i].len = this_len;
 652                if (!this_len) {
 653                        __free_page(spd.pages[i]);
 654                        spd.pages[i] = NULL;
 655                        nr_freed++;
 656                }
 657                res -= this_len;
 658        }
 659        spd.nr_pages -= nr_freed;
 660
 661        res = splice_to_pipe(pipe, &spd);
 662        if (res > 0)
 663                *ppos += res;
 664
 665shrink_ret:
 666        if (vec != __vec)
 667                kfree(vec);
 668        splice_shrink_spd(pipe, &spd);
 669        return res;
 670
 671err:
 672        for (i = 0; i < spd.nr_pages; i++)
 673                __free_page(spd.pages[i]);
 674
 675        res = error;
 676        goto shrink_ret;
 677}
 678EXPORT_SYMBOL(default_file_splice_read);
 679
 680/*
 681 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 682 * using sendpage(). Return the number of bytes sent.
 683 */
 684static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 685                            struct pipe_buffer *buf, struct splice_desc *sd)
 686{
 687        struct file *file = sd->u.file;
 688        loff_t pos = sd->pos;
 689        int more;
 690
 691        if (!likely(file->f_op && file->f_op->sendpage))
 692                return -EINVAL;
 693
 694        more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 695        return file->f_op->sendpage(file, buf->page, buf->offset,
 696                                    sd->len, &pos, more);
 697}
 698
 699/*
 700 * This is a little more tricky than the file -> pipe splicing. There are
 701 * basically three cases:
 702 *
 703 *      - Destination page already exists in the address space and there
 704 *        are users of it. For that case we have no other option that
 705 *        copying the data. Tough luck.
 706 *      - Destination page already exists in the address space, but there
 707 *        are no users of it. Make sure it's uptodate, then drop it. Fall
 708 *        through to last case.
 709 *      - Destination page does not exist, we can add the pipe page to
 710 *        the page cache and avoid the copy.
 711 *
 712 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 713 * sd->flags), we attempt to migrate pages from the pipe to the output
 714 * file address space page cache. This is possible if no one else has
 715 * the pipe page referenced outside of the pipe and page cache. If
 716 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 717 * a new page in the output file page cache and fill/dirty that.
 718 */
 719int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 720                 struct splice_desc *sd)
 721{
 722        struct file *file = sd->u.file;
 723        struct address_space *mapping = file->f_mapping;
 724        unsigned int offset, this_len;
 725        struct page *page;
 726        void *fsdata;
 727        int ret;
 728
 729        offset = sd->pos & ~PAGE_CACHE_MASK;
 730
 731        this_len = sd->len;
 732        if (this_len + offset > PAGE_CACHE_SIZE)
 733                this_len = PAGE_CACHE_SIZE - offset;
 734
 735        ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 736                                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 737        if (unlikely(ret))
 738                goto out;
 739
 740        if (buf->page != page) {
 741                /*
 742                 * Careful, ->map() uses KM_USER0!
 743                 */
 744                char *src = buf->ops->map(pipe, buf, 1);
 745                char *dst = kmap_atomic(page, KM_USER1);
 746
 747                memcpy(dst + offset, src + buf->offset, this_len);
 748                flush_dcache_page(page);
 749                kunmap_atomic(dst, KM_USER1);
 750                buf->ops->unmap(pipe, buf, src);
 751        }
 752        ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 753                                page, fsdata);
 754out:
 755        return ret;
 756}
 757EXPORT_SYMBOL(pipe_to_file);
 758
 759static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 760{
 761        smp_mb();
 762        if (waitqueue_active(&pipe->wait))
 763                wake_up_interruptible(&pipe->wait);
 764        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 765}
 766
 767/**
 768 * splice_from_pipe_feed - feed available data from a pipe to a file
 769 * @pipe:       pipe to splice from
 770 * @sd:         information to @actor
 771 * @actor:      handler that splices the data
 772 *
 773 * Description:
 774 *    This function loops over the pipe and calls @actor to do the
 775 *    actual moving of a single struct pipe_buffer to the desired
 776 *    destination.  It returns when there's no more buffers left in
 777 *    the pipe or if the requested number of bytes (@sd->total_len)
 778 *    have been copied.  It returns a positive number (one) if the
 779 *    pipe needs to be filled with more data, zero if the required
 780 *    number of bytes have been copied and -errno on error.
 781 *
 782 *    This, together with splice_from_pipe_{begin,end,next}, may be
 783 *    used to implement the functionality of __splice_from_pipe() when
 784 *    locking is required around copying the pipe buffers to the
 785 *    destination.
 786 */
 787int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 788                          splice_actor *actor)
 789{
 790        int ret;
 791
 792        while (pipe->nrbufs) {
 793                struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 794                const struct pipe_buf_operations *ops = buf->ops;
 795
 796                sd->len = buf->len;
 797                if (sd->len > sd->total_len)
 798                        sd->len = sd->total_len;
 799
 800                ret = buf->ops->confirm(pipe, buf);
 801                if (unlikely(ret)) {
 802                        if (ret == -ENODATA)
 803                                ret = 0;
 804                        return ret;
 805                }
 806
 807                ret = actor(pipe, buf, sd);
 808                if (ret <= 0)
 809                        return ret;
 810
 811                buf->offset += ret;
 812                buf->len -= ret;
 813
 814                sd->num_spliced += ret;
 815                sd->len -= ret;
 816                sd->pos += ret;
 817                sd->total_len -= ret;
 818
 819                if (!buf->len) {
 820                        buf->ops = NULL;
 821                        ops->release(pipe, buf);
 822                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 823                        pipe->nrbufs--;
 824                        if (pipe->inode)
 825                                sd->need_wakeup = true;
 826                }
 827
 828                if (!sd->total_len)
 829                        return 0;
 830        }
 831
 832        return 1;
 833}
 834EXPORT_SYMBOL(splice_from_pipe_feed);
 835
 836/**
 837 * splice_from_pipe_next - wait for some data to splice from
 838 * @pipe:       pipe to splice from
 839 * @sd:         information about the splice operation
 840 *
 841 * Description:
 842 *    This function will wait for some data and return a positive
 843 *    value (one) if pipe buffers are available.  It will return zero
 844 *    or -errno if no more data needs to be spliced.
 845 */
 846int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 847{
 848        while (!pipe->nrbufs) {
 849                if (!pipe->writers)
 850                        return 0;
 851
 852                if (!pipe->waiting_writers && sd->num_spliced)
 853                        return 0;
 854
 855                if (sd->flags & SPLICE_F_NONBLOCK)
 856                        return -EAGAIN;
 857
 858                if (signal_pending(current))
 859                        return -ERESTARTSYS;
 860
 861                if (sd->need_wakeup) {
 862                        wakeup_pipe_writers(pipe);
 863                        sd->need_wakeup = false;
 864                }
 865
 866                pipe_wait(pipe);
 867        }
 868
 869        return 1;
 870}
 871EXPORT_SYMBOL(splice_from_pipe_next);
 872
 873/**
 874 * splice_from_pipe_begin - start splicing from pipe
 875 * @sd:         information about the splice operation
 876 *
 877 * Description:
 878 *    This function should be called before a loop containing
 879 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 880 *    initialize the necessary fields of @sd.
 881 */
 882void splice_from_pipe_begin(struct splice_desc *sd)
 883{
 884        sd->num_spliced = 0;
 885        sd->need_wakeup = false;
 886}
 887EXPORT_SYMBOL(splice_from_pipe_begin);
 888
 889/**
 890 * splice_from_pipe_end - finish splicing from pipe
 891 * @pipe:       pipe to splice from
 892 * @sd:         information about the splice operation
 893 *
 894 * Description:
 895 *    This function will wake up pipe writers if necessary.  It should
 896 *    be called after a loop containing splice_from_pipe_next() and
 897 *    splice_from_pipe_feed().
 898 */
 899void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 900{
 901        if (sd->need_wakeup)
 902                wakeup_pipe_writers(pipe);
 903}
 904EXPORT_SYMBOL(splice_from_pipe_end);
 905
 906/**
 907 * __splice_from_pipe - splice data from a pipe to given actor
 908 * @pipe:       pipe to splice from
 909 * @sd:         information to @actor
 910 * @actor:      handler that splices the data
 911 *
 912 * Description:
 913 *    This function does little more than loop over the pipe and call
 914 *    @actor to do the actual moving of a single struct pipe_buffer to
 915 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 916 *    pipe_to_user.
 917 *
 918 */
 919ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 920                           splice_actor *actor)
 921{
 922        int ret;
 923
 924        splice_from_pipe_begin(sd);
 925        do {
 926                ret = splice_from_pipe_next(pipe, sd);
 927                if (ret > 0)
 928                        ret = splice_from_pipe_feed(pipe, sd, actor);
 929        } while (ret > 0);
 930        splice_from_pipe_end(pipe, sd);
 931
 932        return sd->num_spliced ? sd->num_spliced : ret;
 933}
 934EXPORT_SYMBOL(__splice_from_pipe);
 935
 936/**
 937 * splice_from_pipe - splice data from a pipe to a file
 938 * @pipe:       pipe to splice from
 939 * @out:        file to splice to
 940 * @ppos:       position in @out
 941 * @len:        how many bytes to splice
 942 * @flags:      splice modifier flags
 943 * @actor:      handler that splices the data
 944 *
 945 * Description:
 946 *    See __splice_from_pipe. This function locks the pipe inode,
 947 *    otherwise it's identical to __splice_from_pipe().
 948 *
 949 */
 950ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 951                         loff_t *ppos, size_t len, unsigned int flags,
 952                         splice_actor *actor)
 953{
 954        ssize_t ret;
 955        struct splice_desc sd = {
 956                .total_len = len,
 957                .flags = flags,
 958                .pos = *ppos,
 959                .u.file = out,
 960        };
 961
 962        pipe_lock(pipe);
 963        ret = __splice_from_pipe(pipe, &sd, actor);
 964        pipe_unlock(pipe);
 965
 966        return ret;
 967}
 968
 969/**
 970 * generic_file_splice_write - splice data from a pipe to a file
 971 * @pipe:       pipe info
 972 * @out:        file to write to
 973 * @ppos:       position in @out
 974 * @len:        number of bytes to splice
 975 * @flags:      splice modifier flags
 976 *
 977 * Description:
 978 *    Will either move or copy pages (determined by @flags options) from
 979 *    the given pipe inode to the given file.
 980 *
 981 */
 982ssize_t
 983generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 984                          loff_t *ppos, size_t len, unsigned int flags)
 985{
 986        struct address_space *mapping = out->f_mapping;
 987        struct inode *inode = mapping->host;
 988        struct splice_desc sd = {
 989                .total_len = len,
 990                .flags = flags,
 991                .pos = *ppos,
 992                .u.file = out,
 993        };
 994        ssize_t ret;
 995
 996        pipe_lock(pipe);
 997
 998        splice_from_pipe_begin(&sd);
 999        do {
1000                ret = splice_from_pipe_next(pipe, &sd);
1001                if (ret <= 0)
1002                        break;
1003
1004                mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1005                ret = file_remove_suid(out);
1006                if (!ret) {
1007                        file_update_time(out);
1008                        ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1009                }
1010                mutex_unlock(&inode->i_mutex);
1011        } while (ret > 0);
1012        splice_from_pipe_end(pipe, &sd);
1013
1014        pipe_unlock(pipe);
1015
1016        if (sd.num_spliced)
1017                ret = sd.num_spliced;
1018
1019        if (ret > 0) {
1020                unsigned long nr_pages;
1021                int err;
1022
1023                nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1024
1025                err = generic_write_sync(out, *ppos, ret);
1026                if (err)
1027                        ret = err;
1028                else
1029                        *ppos += ret;
1030                balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1031        }
1032
1033        return ret;
1034}
1035
1036EXPORT_SYMBOL(generic_file_splice_write);
1037
1038static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1039                          struct splice_desc *sd)
1040{
1041        int ret;
1042        void *data;
1043
1044        data = buf->ops->map(pipe, buf, 0);
1045        ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1046        buf->ops->unmap(pipe, buf, data);
1047
1048        return ret;
1049}
1050
1051static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1052                                         struct file *out, loff_t *ppos,
1053                                         size_t len, unsigned int flags)
1054{
1055        ssize_t ret;
1056
1057        ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1058        if (ret > 0)
1059                *ppos += ret;
1060
1061        return ret;
1062}
1063
1064/**
1065 * generic_splice_sendpage - splice data from a pipe to a socket
1066 * @pipe:       pipe to splice from
1067 * @out:        socket to write to
1068 * @ppos:       position in @out
1069 * @len:        number of bytes to splice
1070 * @flags:      splice modifier flags
1071 *
1072 * Description:
1073 *    Will send @len bytes from the pipe to a network socket. No data copying
1074 *    is involved.
1075 *
1076 */
1077ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1078                                loff_t *ppos, size_t len, unsigned int flags)
1079{
1080        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1081}
1082
1083EXPORT_SYMBOL(generic_splice_sendpage);
1084
1085/*
1086 * Attempt to initiate a splice from pipe to file.
1087 */
1088static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1089                           loff_t *ppos, size_t len, unsigned int flags)
1090{
1091        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1092                                loff_t *, size_t, unsigned int);
1093        int ret;
1094
1095        if (unlikely(!(out->f_mode & FMODE_WRITE)))
1096                return -EBADF;
1097
1098        if (unlikely(out->f_flags & O_APPEND))
1099                return -EINVAL;
1100
1101        ret = rw_verify_area(WRITE, out, ppos, len);
1102        if (unlikely(ret < 0))
1103                return ret;
1104
1105        if (out->f_op && out->f_op->splice_write)
1106                splice_write = out->f_op->splice_write;
1107        else
1108                splice_write = default_file_splice_write;
1109
1110        return splice_write(pipe, out, ppos, len, flags);
1111}
1112
1113/*
1114 * Attempt to initiate a splice from a file to a pipe.
1115 */
1116static long do_splice_to(struct file *in, loff_t *ppos,
1117                         struct pipe_inode_info *pipe, size_t len,
1118                         unsigned int flags)
1119{
1120        ssize_t (*splice_read)(struct file *, loff_t *,
1121                               struct pipe_inode_info *, size_t, unsigned int);
1122        int ret;
1123
1124        if (unlikely(!(in->f_mode & FMODE_READ)))
1125                return -EBADF;
1126
1127        ret = rw_verify_area(READ, in, ppos, len);
1128        if (unlikely(ret < 0))
1129                return ret;
1130
1131        if (in->f_op && in->f_op->splice_read)
1132                splice_read = in->f_op->splice_read;
1133        else
1134                splice_read = default_file_splice_read;
1135
1136        return splice_read(in, ppos, pipe, len, flags);
1137}
1138
1139/**
1140 * splice_direct_to_actor - splices data directly between two non-pipes
1141 * @in:         file to splice from
1142 * @sd:         actor information on where to splice to
1143 * @actor:      handles the data splicing
1144 *
1145 * Description:
1146 *    This is a special case helper to splice directly between two
1147 *    points, without requiring an explicit pipe. Internally an allocated
1148 *    pipe is cached in the process, and reused during the lifetime of
1149 *    that process.
1150 *
1151 */
1152ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1153                               splice_direct_actor *actor)
1154{
1155        struct pipe_inode_info *pipe;
1156        long ret, bytes;
1157        umode_t i_mode;
1158        size_t len;
1159        int i, flags;
1160
1161        /*
1162         * We require the input being a regular file, as we don't want to
1163         * randomly drop data for eg socket -> socket splicing. Use the
1164         * piped splicing for that!
1165         */
1166        i_mode = in->f_path.dentry->d_inode->i_mode;
1167        if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1168                return -EINVAL;
1169
1170        /*
1171         * neither in nor out is a pipe, setup an internal pipe attached to
1172         * 'out' and transfer the wanted data from 'in' to 'out' through that
1173         */
1174        pipe = current->splice_pipe;
1175        if (unlikely(!pipe)) {
1176                pipe = alloc_pipe_info(NULL);
1177                if (!pipe)
1178                        return -ENOMEM;
1179
1180                /*
1181                 * We don't have an immediate reader, but we'll read the stuff
1182                 * out of the pipe right after the splice_to_pipe(). So set
1183                 * PIPE_READERS appropriately.
1184                 */
1185                pipe->readers = 1;
1186
1187                current->splice_pipe = pipe;
1188        }
1189
1190        /*
1191         * Do the splice.
1192         */
1193        ret = 0;
1194        bytes = 0;
1195        len = sd->total_len;
1196        flags = sd->flags;
1197
1198        /*
1199         * Don't block on output, we have to drain the direct pipe.
1200         */
1201        sd->flags &= ~SPLICE_F_NONBLOCK;
1202
1203        while (len) {
1204                size_t read_len;
1205                loff_t pos = sd->pos, prev_pos = pos;
1206
1207                ret = do_splice_to(in, &pos, pipe, len, flags);
1208                if (unlikely(ret <= 0))
1209                        goto out_release;
1210
1211                read_len = ret;
1212                sd->total_len = read_len;
1213
1214                /*
1215                 * NOTE: nonblocking mode only applies to the input. We
1216                 * must not do the output in nonblocking mode as then we
1217                 * could get stuck data in the internal pipe:
1218                 */
1219                ret = actor(pipe, sd);
1220                if (unlikely(ret <= 0)) {
1221                        sd->pos = prev_pos;
1222                        goto out_release;
1223                }
1224
1225                bytes += ret;
1226                len -= ret;
1227                sd->pos = pos;
1228
1229                if (ret < read_len) {
1230                        sd->pos = prev_pos + ret;
1231                        goto out_release;
1232                }
1233        }
1234
1235done:
1236        pipe->nrbufs = pipe->curbuf = 0;
1237        file_accessed(in);
1238        return bytes;
1239
1240out_release:
1241        /*
1242         * If we did an incomplete transfer we must release
1243         * the pipe buffers in question:
1244         */
1245        for (i = 0; i < pipe->buffers; i++) {
1246                struct pipe_buffer *buf = pipe->bufs + i;
1247
1248                if (buf->ops) {
1249                        buf->ops->release(pipe, buf);
1250                        buf->ops = NULL;
1251                }
1252        }
1253
1254        if (!bytes)
1255                bytes = ret;
1256
1257        goto done;
1258}
1259EXPORT_SYMBOL(splice_direct_to_actor);
1260
1261static int direct_splice_actor(struct pipe_inode_info *pipe,
1262                               struct splice_desc *sd)
1263{
1264        struct file *file = sd->u.file;
1265
1266        return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1267                              sd->flags);
1268}
1269
1270/**
1271 * do_splice_direct - splices data directly between two files
1272 * @in:         file to splice from
1273 * @ppos:       input file offset
1274 * @out:        file to splice to
1275 * @len:        number of bytes to splice
1276 * @flags:      splice modifier flags
1277 *
1278 * Description:
1279 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1280 *    doing it in the application would incur an extra system call
1281 *    (splice in + splice out, as compared to just sendfile()). So this helper
1282 *    can splice directly through a process-private pipe.
1283 *
1284 */
1285long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1286                      size_t len, unsigned int flags)
1287{
1288        struct splice_desc sd = {
1289                .len            = len,
1290                .total_len      = len,
1291                .flags          = flags,
1292                .pos            = *ppos,
1293                .u.file         = out,
1294        };
1295        long ret;
1296
1297        ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1298        if (ret > 0)
1299                *ppos = sd.pos;
1300
1301        return ret;
1302}
1303
1304static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1305                               struct pipe_inode_info *opipe,
1306                               size_t len, unsigned int flags);
1307
1308/*
1309 * Determine where to splice to/from.
1310 */
1311static long do_splice(struct file *in, loff_t __user *off_in,
1312                      struct file *out, loff_t __user *off_out,
1313                      size_t len, unsigned int flags)
1314{
1315        struct pipe_inode_info *ipipe;
1316        struct pipe_inode_info *opipe;
1317        loff_t offset, *off;
1318        long ret;
1319
1320        ipipe = get_pipe_info(in);
1321        opipe = get_pipe_info(out);
1322
1323        if (ipipe && opipe) {
1324                if (off_in || off_out)
1325                        return -ESPIPE;
1326
1327                if (!(in->f_mode & FMODE_READ))
1328                        return -EBADF;
1329
1330                if (!(out->f_mode & FMODE_WRITE))
1331                        return -EBADF;
1332
1333                /* Splicing to self would be fun, but... */
1334                if (ipipe == opipe)
1335                        return -EINVAL;
1336
1337                return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1338        }
1339
1340        if (ipipe) {
1341                if (off_in)
1342                        return -ESPIPE;
1343                if (off_out) {
1344                        if (!(out->f_mode & FMODE_PWRITE))
1345                                return -EINVAL;
1346                        if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1347                                return -EFAULT;
1348                        off = &offset;
1349                } else
1350                        off = &out->f_pos;
1351
1352                ret = do_splice_from(ipipe, out, off, len, flags);
1353
1354                if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1355                        ret = -EFAULT;
1356
1357                return ret;
1358        }
1359
1360        if (opipe) {
1361                if (off_out)
1362                        return -ESPIPE;
1363                if (off_in) {
1364                        if (!(in->f_mode & FMODE_PREAD))
1365                                return -EINVAL;
1366                        if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1367                                return -EFAULT;
1368                        off = &offset;
1369                } else
1370                        off = &in->f_pos;
1371
1372                ret = do_splice_to(in, off, opipe, len, flags);
1373
1374                if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1375                        ret = -EFAULT;
1376
1377                return ret;
1378        }
1379
1380        return -EINVAL;
1381}
1382
1383/*
1384 * Map an iov into an array of pages and offset/length tupples. With the
1385 * partial_page structure, we can map several non-contiguous ranges into
1386 * our ones pages[] map instead of splitting that operation into pieces.
1387 * Could easily be exported as a generic helper for other users, in which
1388 * case one would probably want to add a 'max_nr_pages' parameter as well.
1389 */
1390static int get_iovec_page_array(const struct iovec __user *iov,
1391                                unsigned int nr_vecs, struct page **pages,
1392                                struct partial_page *partial, int aligned,
1393                                unsigned int pipe_buffers)
1394{
1395        int buffers = 0, error = 0;
1396
1397        while (nr_vecs) {
1398                unsigned long off, npages;
1399                struct iovec entry;
1400                void __user *base;
1401                size_t len;
1402                int i;
1403
1404                error = -EFAULT;
1405                if (copy_from_user(&entry, iov, sizeof(entry)))
1406                        break;
1407
1408                base = entry.iov_base;
1409                len = entry.iov_len;
1410
1411                /*
1412                 * Sanity check this iovec. 0 read succeeds.
1413                 */
1414                error = 0;
1415                if (unlikely(!len))
1416                        break;
1417                error = -EFAULT;
1418                if (!access_ok(VERIFY_READ, base, len))
1419                        break;
1420
1421                /*
1422                 * Get this base offset and number of pages, then map
1423                 * in the user pages.
1424                 */
1425                off = (unsigned long) base & ~PAGE_MASK;
1426
1427                /*
1428                 * If asked for alignment, the offset must be zero and the
1429                 * length a multiple of the PAGE_SIZE.
1430                 */
1431                error = -EINVAL;
1432                if (aligned && (off || len & ~PAGE_MASK))
1433                        break;
1434
1435                npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1436                if (npages > pipe_buffers - buffers)
1437                        npages = pipe_buffers - buffers;
1438
1439                error = get_user_pages_fast((unsigned long)base, npages,
1440                                        0, &pages[buffers]);
1441
1442                if (unlikely(error <= 0))
1443                        break;
1444
1445                /*
1446                 * Fill this contiguous range into the partial page map.
1447                 */
1448                for (i = 0; i < error; i++) {
1449                        const int plen = min_t(size_t, len, PAGE_SIZE - off);
1450
1451                        partial[buffers].offset = off;
1452                        partial[buffers].len = plen;
1453
1454                        off = 0;
1455                        len -= plen;
1456                        buffers++;
1457                }
1458
1459                /*
1460                 * We didn't complete this iov, stop here since it probably
1461                 * means we have to move some of this into a pipe to
1462                 * be able to continue.
1463                 */
1464                if (len)
1465                        break;
1466
1467                /*
1468                 * Don't continue if we mapped fewer pages than we asked for,
1469                 * or if we mapped the max number of pages that we have
1470                 * room for.
1471                 */
1472                if (error < npages || buffers == pipe_buffers)
1473                        break;
1474
1475                nr_vecs--;
1476                iov++;
1477        }
1478
1479        if (buffers)
1480                return buffers;
1481
1482        return error;
1483}
1484
1485static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1486                        struct splice_desc *sd)
1487{
1488        char *src;
1489        int ret;
1490
1491        /*
1492         * See if we can use the atomic maps, by prefaulting in the
1493         * pages and doing an atomic copy
1494         */
1495        if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1496                src = buf->ops->map(pipe, buf, 1);
1497                ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1498                                                        sd->len);
1499                buf->ops->unmap(pipe, buf, src);
1500                if (!ret) {
1501                        ret = sd->len;
1502                        goto out;
1503                }
1504        }
1505
1506        /*
1507         * No dice, use slow non-atomic map and copy
1508         */
1509        src = buf->ops->map(pipe, buf, 0);
1510
1511        ret = sd->len;
1512        if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1513                ret = -EFAULT;
1514
1515        buf->ops->unmap(pipe, buf, src);
1516out:
1517        if (ret > 0)
1518                sd->u.userptr += ret;
1519        return ret;
1520}
1521
1522/*
1523 * For lack of a better implementation, implement vmsplice() to userspace
1524 * as a simple copy of the pipes pages to the user iov.
1525 */
1526static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1527                             unsigned long nr_segs, unsigned int flags)
1528{
1529        struct pipe_inode_info *pipe;
1530        struct splice_desc sd;
1531        ssize_t size;
1532        int error;
1533        long ret;
1534
1535        pipe = get_pipe_info(file);
1536        if (!pipe)
1537                return -EBADF;
1538
1539        pipe_lock(pipe);
1540
1541        error = ret = 0;
1542        while (nr_segs) {
1543                void __user *base;
1544                size_t len;
1545
1546                /*
1547                 * Get user address base and length for this iovec.
1548                 */
1549                error = get_user(base, &iov->iov_base);
1550                if (unlikely(error))
1551                        break;
1552                error = get_user(len, &iov->iov_len);
1553                if (unlikely(error))
1554                        break;
1555
1556                /*
1557                 * Sanity check this iovec. 0 read succeeds.
1558                 */
1559                if (unlikely(!len))
1560                        break;
1561                if (unlikely(!base)) {
1562                        error = -EFAULT;
1563                        break;
1564                }
1565
1566                if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1567                        error = -EFAULT;
1568                        break;
1569                }
1570
1571                sd.len = 0;
1572                sd.total_len = len;
1573                sd.flags = flags;
1574                sd.u.userptr = base;
1575                sd.pos = 0;
1576
1577                size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1578                if (size < 0) {
1579                        if (!ret)
1580                                ret = size;
1581
1582                        break;
1583                }
1584
1585                ret += size;
1586
1587                if (size < len)
1588                        break;
1589
1590                nr_segs--;
1591                iov++;
1592        }
1593
1594        pipe_unlock(pipe);
1595
1596        if (!ret)
1597                ret = error;
1598
1599        return ret;
1600}
1601
1602/*
1603 * vmsplice splices a user address range into a pipe. It can be thought of
1604 * as splice-from-memory, where the regular splice is splice-from-file (or
1605 * to file). In both cases the output is a pipe, naturally.
1606 */
1607static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1608                             unsigned long nr_segs, unsigned int flags)
1609{
1610        struct pipe_inode_info *pipe;
1611        struct page *pages[PIPE_DEF_BUFFERS];
1612        struct partial_page partial[PIPE_DEF_BUFFERS];
1613        struct splice_pipe_desc spd = {
1614                .pages = pages,
1615                .partial = partial,
1616                .flags = flags,
1617                .ops = &user_page_pipe_buf_ops,
1618                .spd_release = spd_release_page,
1619        };
1620        long ret;
1621
1622        pipe = get_pipe_info(file);
1623        if (!pipe)
1624                return -EBADF;
1625
1626        if (splice_grow_spd(pipe, &spd))
1627                return -ENOMEM;
1628
1629        spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1630                                            spd.partial, flags & SPLICE_F_GIFT,
1631                                            pipe->buffers);
1632        if (spd.nr_pages <= 0)
1633                ret = spd.nr_pages;
1634        else
1635                ret = splice_to_pipe(pipe, &spd);
1636
1637        splice_shrink_spd(pipe, &spd);
1638        return ret;
1639}
1640
1641/*
1642 * Note that vmsplice only really supports true splicing _from_ user memory
1643 * to a pipe, not the other way around. Splicing from user memory is a simple
1644 * operation that can be supported without any funky alignment restrictions
1645 * or nasty vm tricks. We simply map in the user memory and fill them into
1646 * a pipe. The reverse isn't quite as easy, though. There are two possible
1647 * solutions for that:
1648 *
1649 *      - memcpy() the data internally, at which point we might as well just
1650 *        do a regular read() on the buffer anyway.
1651 *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1652 *        has restriction limitations on both ends of the pipe).
1653 *
1654 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1655 *
1656 */
1657SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1658                unsigned long, nr_segs, unsigned int, flags)
1659{
1660        struct file *file;
1661        long error;
1662        int fput;
1663
1664        if (unlikely(nr_segs > UIO_MAXIOV))
1665                return -EINVAL;
1666        else if (unlikely(!nr_segs))
1667                return 0;
1668
1669        error = -EBADF;
1670        file = fget_light(fd, &fput);
1671        if (file) {
1672                if (file->f_mode & FMODE_WRITE)
1673                        error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1674                else if (file->f_mode & FMODE_READ)
1675                        error = vmsplice_to_user(file, iov, nr_segs, flags);
1676
1677                fput_light(file, fput);
1678        }
1679
1680        return error;
1681}
1682
1683SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1684                int, fd_out, loff_t __user *, off_out,
1685                size_t, len, unsigned int, flags)
1686{
1687        long error;
1688        struct file *in, *out;
1689        int fput_in, fput_out;
1690
1691        if (unlikely(!len))
1692                return 0;
1693
1694        error = -EBADF;
1695        in = fget_light(fd_in, &fput_in);
1696        if (in) {
1697                if (in->f_mode & FMODE_READ) {
1698                        out = fget_light(fd_out, &fput_out);
1699                        if (out) {
1700                                if (out->f_mode & FMODE_WRITE)
1701                                        error = do_splice(in, off_in,
1702                                                          out, off_out,
1703                                                          len, flags);
1704                                fput_light(out, fput_out);
1705                        }
1706                }
1707
1708                fput_light(in, fput_in);
1709        }
1710
1711        return error;
1712}
1713
1714/*
1715 * Make sure there's data to read. Wait for input if we can, otherwise
1716 * return an appropriate error.
1717 */
1718static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1719{
1720        int ret;
1721
1722        /*
1723         * Check ->nrbufs without the inode lock first. This function
1724         * is speculative anyways, so missing one is ok.
1725         */
1726        if (pipe->nrbufs)
1727                return 0;
1728
1729        ret = 0;
1730        pipe_lock(pipe);
1731
1732        while (!pipe->nrbufs) {
1733                if (signal_pending(current)) {
1734                        ret = -ERESTARTSYS;
1735                        break;
1736                }
1737                if (!pipe->writers)
1738                        break;
1739                if (!pipe->waiting_writers) {
1740                        if (flags & SPLICE_F_NONBLOCK) {
1741                                ret = -EAGAIN;
1742                                break;
1743                        }
1744                }
1745                pipe_wait(pipe);
1746        }
1747
1748        pipe_unlock(pipe);
1749        return ret;
1750}
1751
1752/*
1753 * Make sure there's writeable room. Wait for room if we can, otherwise
1754 * return an appropriate error.
1755 */
1756static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1757{
1758        int ret;
1759
1760        /*
1761         * Check ->nrbufs without the inode lock first. This function
1762         * is speculative anyways, so missing one is ok.
1763         */
1764        if (pipe->nrbufs < pipe->buffers)
1765                return 0;
1766
1767        ret = 0;
1768        pipe_lock(pipe);
1769
1770        while (pipe->nrbufs >= pipe->buffers) {
1771                if (!pipe->readers) {
1772                        send_sig(SIGPIPE, current, 0);
1773                        ret = -EPIPE;
1774                        break;
1775                }
1776                if (flags & SPLICE_F_NONBLOCK) {
1777                        ret = -EAGAIN;
1778                        break;
1779                }
1780                if (signal_pending(current)) {
1781                        ret = -ERESTARTSYS;
1782                        break;
1783                }
1784                pipe->waiting_writers++;
1785                pipe_wait(pipe);
1786                pipe->waiting_writers--;
1787        }
1788
1789        pipe_unlock(pipe);
1790        return ret;
1791}
1792
1793/*
1794 * Splice contents of ipipe to opipe.
1795 */
1796static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1797                               struct pipe_inode_info *opipe,
1798                               size_t len, unsigned int flags)
1799{
1800        struct pipe_buffer *ibuf, *obuf;
1801        int ret = 0, nbuf;
1802        bool input_wakeup = false;
1803
1804
1805retry:
1806        ret = ipipe_prep(ipipe, flags);
1807        if (ret)
1808                return ret;
1809
1810        ret = opipe_prep(opipe, flags);
1811        if (ret)
1812                return ret;
1813
1814        /*
1815         * Potential ABBA deadlock, work around it by ordering lock
1816         * grabbing by pipe info address. Otherwise two different processes
1817         * could deadlock (one doing tee from A -> B, the other from B -> A).
1818         */
1819        pipe_double_lock(ipipe, opipe);
1820
1821        do {
1822                if (!opipe->readers) {
1823                        send_sig(SIGPIPE, current, 0);
1824                        if (!ret)
1825                                ret = -EPIPE;
1826                        break;
1827                }
1828
1829                if (!ipipe->nrbufs && !ipipe->writers)
1830                        break;
1831
1832                /*
1833                 * Cannot make any progress, because either the input
1834                 * pipe is empty or the output pipe is full.
1835                 */
1836                if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1837                        /* Already processed some buffers, break */
1838                        if (ret)
1839                                break;
1840
1841                        if (flags & SPLICE_F_NONBLOCK) {
1842                                ret = -EAGAIN;
1843                                break;
1844                        }
1845
1846                        /*
1847                         * We raced with another reader/writer and haven't
1848                         * managed to process any buffers.  A zero return
1849                         * value means EOF, so retry instead.
1850                         */
1851                        pipe_unlock(ipipe);
1852                        pipe_unlock(opipe);
1853                        goto retry;
1854                }
1855
1856                ibuf = ipipe->bufs + ipipe->curbuf;
1857                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1858                obuf = opipe->bufs + nbuf;
1859
1860                if (len >= ibuf->len) {
1861                        /*
1862                         * Simply move the whole buffer from ipipe to opipe
1863                         */
1864                        *obuf = *ibuf;
1865                        ibuf->ops = NULL;
1866                        opipe->nrbufs++;
1867                        ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1868                        ipipe->nrbufs--;
1869                        input_wakeup = true;
1870                } else {
1871                        /*
1872                         * Get a reference to this pipe buffer,
1873                         * so we can copy the contents over.
1874                         */
1875                        ibuf->ops->get(ipipe, ibuf);
1876                        *obuf = *ibuf;
1877
1878                        /*
1879                         * Don't inherit the gift flag, we need to
1880                         * prevent multiple steals of this page.
1881                         */
1882                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1883
1884                        obuf->len = len;
1885                        opipe->nrbufs++;
1886                        ibuf->offset += obuf->len;
1887                        ibuf->len -= obuf->len;
1888                }
1889                ret += obuf->len;
1890                len -= obuf->len;
1891        } while (len);
1892
1893        pipe_unlock(ipipe);
1894        pipe_unlock(opipe);
1895
1896        /*
1897         * If we put data in the output pipe, wakeup any potential readers.
1898         */
1899        if (ret > 0)
1900                wakeup_pipe_readers(opipe);
1901
1902        if (input_wakeup)
1903                wakeup_pipe_writers(ipipe);
1904
1905        return ret;
1906}
1907
1908/*
1909 * Link contents of ipipe to opipe.
1910 */
1911static int link_pipe(struct pipe_inode_info *ipipe,
1912                     struct pipe_inode_info *opipe,
1913                     size_t len, unsigned int flags)
1914{
1915        struct pipe_buffer *ibuf, *obuf;
1916        int ret = 0, i = 0, nbuf;
1917
1918        /*
1919         * Potential ABBA deadlock, work around it by ordering lock
1920         * grabbing by pipe info address. Otherwise two different processes
1921         * could deadlock (one doing tee from A -> B, the other from B -> A).
1922         */
1923        pipe_double_lock(ipipe, opipe);
1924
1925        do {
1926                if (!opipe->readers) {
1927                        send_sig(SIGPIPE, current, 0);
1928                        if (!ret)
1929                                ret = -EPIPE;
1930                        break;
1931                }
1932
1933                /*
1934                 * If we have iterated all input buffers or ran out of
1935                 * output room, break.
1936                 */
1937                if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1938                        break;
1939
1940                ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1941                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1942
1943                /*
1944                 * Get a reference to this pipe buffer,
1945                 * so we can copy the contents over.
1946                 */
1947                ibuf->ops->get(ipipe, ibuf);
1948
1949                obuf = opipe->bufs + nbuf;
1950                *obuf = *ibuf;
1951
1952                /*
1953                 * Don't inherit the gift flag, we need to
1954                 * prevent multiple steals of this page.
1955                 */
1956                obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1957
1958                if (obuf->len > len)
1959                        obuf->len = len;
1960
1961                opipe->nrbufs++;
1962                ret += obuf->len;
1963                len -= obuf->len;
1964                i++;
1965        } while (len);
1966
1967        /*
1968         * return EAGAIN if we have the potential of some data in the
1969         * future, otherwise just return 0
1970         */
1971        if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1972                ret = -EAGAIN;
1973
1974        pipe_unlock(ipipe);
1975        pipe_unlock(opipe);
1976
1977        /*
1978         * If we put data in the output pipe, wakeup any potential readers.
1979         */
1980        if (ret > 0)
1981                wakeup_pipe_readers(opipe);
1982
1983        return ret;
1984}
1985
1986/*
1987 * This is a tee(1) implementation that works on pipes. It doesn't copy
1988 * any data, it simply references the 'in' pages on the 'out' pipe.
1989 * The 'flags' used are the SPLICE_F_* variants, currently the only
1990 * applicable one is SPLICE_F_NONBLOCK.
1991 */
1992static long do_tee(struct file *in, struct file *out, size_t len,
1993                   unsigned int flags)
1994{
1995        struct pipe_inode_info *ipipe = get_pipe_info(in);
1996        struct pipe_inode_info *opipe = get_pipe_info(out);
1997        int ret = -EINVAL;
1998
1999        /*
2000         * Duplicate the contents of ipipe to opipe without actually
2001         * copying the data.
2002         */
2003        if (ipipe && opipe && ipipe != opipe) {
2004                /*
2005                 * Keep going, unless we encounter an error. The ipipe/opipe
2006                 * ordering doesn't really matter.
2007                 */
2008                ret = ipipe_prep(ipipe, flags);
2009                if (!ret) {
2010                        ret = opipe_prep(opipe, flags);
2011                        if (!ret)
2012                                ret = link_pipe(ipipe, opipe, len, flags);
2013                }
2014        }
2015
2016        return ret;
2017}
2018
2019SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2020{
2021        struct file *in;
2022        int error, fput_in;
2023
2024        if (unlikely(!len))
2025                return 0;
2026
2027        error = -EBADF;
2028        in = fget_light(fdin, &fput_in);
2029        if (in) {
2030                if (in->f_mode & FMODE_READ) {
2031                        int fput_out;
2032                        struct file *out = fget_light(fdout, &fput_out);
2033
2034                        if (out) {
2035                                if (out->f_mode & FMODE_WRITE)
2036                                        error = do_tee(in, out, len, flags);
2037                                fput_light(out, fput_out);
2038                        }
2039                }
2040                fput_light(in, fput_in);
2041        }
2042
2043        return error;
2044}
2045
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