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 int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
 559                                    struct pipe_buffer *buf)
 560{
 561        return 1;
 562}
 563
 564/* Pipe buffer operations for a socket and similar. */
 565const struct pipe_buf_operations nosteal_pipe_buf_ops = {
 566        .can_merge = 0,
 567        .map = generic_pipe_buf_map,
 568        .unmap = generic_pipe_buf_unmap,
 569        .confirm = generic_pipe_buf_confirm,
 570        .release = generic_pipe_buf_release,
 571        .steal = generic_pipe_buf_nosteal,
 572        .get = generic_pipe_buf_get,
 573};
 574EXPORT_SYMBOL(nosteal_pipe_buf_ops);
 575
 576static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 577                            unsigned long vlen, loff_t offset)
 578{
 579        mm_segment_t old_fs;
 580        loff_t pos = offset;
 581        ssize_t res;
 582
 583        old_fs = get_fs();
 584        set_fs(get_ds());
 585        /* The cast to a user pointer is valid due to the set_fs() */
 586        res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 587        set_fs(old_fs);
 588
 589        return res;
 590}
 591
 592ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 593                            loff_t pos)
 594{
 595        mm_segment_t old_fs;
 596        ssize_t res;
 597
 598        old_fs = get_fs();
 599        set_fs(get_ds());
 600        /* The cast to a user pointer is valid due to the set_fs() */
 601        res = vfs_write(file, (__force const char __user *)buf, count, &pos);
 602        set_fs(old_fs);
 603
 604        return res;
 605}
 606EXPORT_SYMBOL(kernel_write);
 607
 608ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 609                                 struct pipe_inode_info *pipe, size_t len,
 610                                 unsigned int flags)
 611{
 612        unsigned int nr_pages;
 613        unsigned int nr_freed;
 614        size_t offset;
 615        struct page *pages[PIPE_DEF_BUFFERS];
 616        struct partial_page partial[PIPE_DEF_BUFFERS];
 617        struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 618        ssize_t res;
 619        size_t this_len;
 620        int error;
 621        int i;
 622        struct splice_pipe_desc spd = {
 623                .pages = pages,
 624                .partial = partial,
 625                .nr_pages_max = PIPE_DEF_BUFFERS,
 626                .flags = flags,
 627                .ops = &default_pipe_buf_ops,
 628                .spd_release = spd_release_page,
 629        };
 630
 631        if (splice_grow_spd(pipe, &spd))
 632                return -ENOMEM;
 633
 634        res = -ENOMEM;
 635        vec = __vec;
 636        if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
 637                vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
 638                if (!vec)
 639                        goto shrink_ret;
 640        }
 641
 642        offset = *ppos & ~PAGE_CACHE_MASK;
 643        nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 644
 645        for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
 646                struct page *page;
 647
 648                page = alloc_page(GFP_USER);
 649                error = -ENOMEM;
 650                if (!page)
 651                        goto err;
 652
 653                this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 654                vec[i].iov_base = (void __user *) page_address(page);
 655                vec[i].iov_len = this_len;
 656                spd.pages[i] = page;
 657                spd.nr_pages++;
 658                len -= this_len;
 659                offset = 0;
 660        }
 661
 662        res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 663        if (res < 0) {
 664                error = res;
 665                goto err;
 666        }
 667
 668        error = 0;
 669        if (!res)
 670                goto err;
 671
 672        nr_freed = 0;
 673        for (i = 0; i < spd.nr_pages; i++) {
 674                this_len = min_t(size_t, vec[i].iov_len, res);
 675                spd.partial[i].offset = 0;
 676                spd.partial[i].len = this_len;
 677                if (!this_len) {
 678                        __free_page(spd.pages[i]);
 679                        spd.pages[i] = NULL;
 680                        nr_freed++;
 681                }
 682                res -= this_len;
 683        }
 684        spd.nr_pages -= nr_freed;
 685
 686        res = splice_to_pipe(pipe, &spd);
 687        if (res > 0)
 688                *ppos += res;
 689
 690shrink_ret:
 691        if (vec != __vec)
 692                kfree(vec);
 693        splice_shrink_spd(&spd);
 694        return res;
 695
 696err:
 697        for (i = 0; i < spd.nr_pages; i++)
 698                __free_page(spd.pages[i]);
 699
 700        res = error;
 701        goto shrink_ret;
 702}
 703EXPORT_SYMBOL(default_file_splice_read);
 704
 705/*
 706 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 707 * using sendpage(). Return the number of bytes sent.
 708 */
 709static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 710                            struct pipe_buffer *buf, struct splice_desc *sd)
 711{
 712        struct file *file = sd->u.file;
 713        loff_t pos = sd->pos;
 714        int more;
 715
 716        if (!likely(file->f_op->sendpage))
 717                return -EINVAL;
 718
 719        more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
 720
 721        if (sd->len < sd->total_len && pipe->nrbufs > 1)
 722                more |= MSG_SENDPAGE_NOTLAST;
 723
 724        return file->f_op->sendpage(file, buf->page, buf->offset,
 725                                    sd->len, &pos, more);
 726}
 727
 728/*
 729 * This is a little more tricky than the file -> pipe splicing. There are
 730 * basically three cases:
 731 *
 732 *      - Destination page already exists in the address space and there
 733 *        are users of it. For that case we have no other option that
 734 *        copying the data. Tough luck.
 735 *      - Destination page already exists in the address space, but there
 736 *        are no users of it. Make sure it's uptodate, then drop it. Fall
 737 *        through to last case.
 738 *      - Destination page does not exist, we can add the pipe page to
 739 *        the page cache and avoid the copy.
 740 *
 741 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 742 * sd->flags), we attempt to migrate pages from the pipe to the output
 743 * file address space page cache. This is possible if no one else has
 744 * the pipe page referenced outside of the pipe and page cache. If
 745 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 746 * a new page in the output file page cache and fill/dirty that.
 747 */
 748int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 749                 struct splice_desc *sd)
 750{
 751        struct file *file = sd->u.file;
 752        struct address_space *mapping = file->f_mapping;
 753        unsigned int offset, this_len;
 754        struct page *page;
 755        void *fsdata;
 756        int ret;
 757
 758        offset = sd->pos & ~PAGE_CACHE_MASK;
 759
 760        this_len = sd->len;
 761        if (this_len + offset > PAGE_CACHE_SIZE)
 762                this_len = PAGE_CACHE_SIZE - offset;
 763
 764        ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 765                                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 766        if (unlikely(ret))
 767                goto out;
 768
 769        if (buf->page != page) {
 770                char *src = buf->ops->map(pipe, buf, 1);
 771                char *dst = kmap_atomic(page);
 772
 773                memcpy(dst + offset, src + buf->offset, this_len);
 774                flush_dcache_page(page);
 775                kunmap_atomic(dst);
 776                buf->ops->unmap(pipe, buf, src);
 777        }
 778        ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 779                                page, fsdata);
 780out:
 781        return ret;
 782}
 783EXPORT_SYMBOL(pipe_to_file);
 784
 785static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 786{
 787        smp_mb();
 788        if (waitqueue_active(&pipe->wait))
 789                wake_up_interruptible(&pipe->wait);
 790        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 791}
 792
 793/**
 794 * splice_from_pipe_feed - feed available data from a pipe to a file
 795 * @pipe:       pipe to splice from
 796 * @sd:         information to @actor
 797 * @actor:      handler that splices the data
 798 *
 799 * Description:
 800 *    This function loops over the pipe and calls @actor to do the
 801 *    actual moving of a single struct pipe_buffer to the desired
 802 *    destination.  It returns when there's no more buffers left in
 803 *    the pipe or if the requested number of bytes (@sd->total_len)
 804 *    have been copied.  It returns a positive number (one) if the
 805 *    pipe needs to be filled with more data, zero if the required
 806 *    number of bytes have been copied and -errno on error.
 807 *
 808 *    This, together with splice_from_pipe_{begin,end,next}, may be
 809 *    used to implement the functionality of __splice_from_pipe() when
 810 *    locking is required around copying the pipe buffers to the
 811 *    destination.
 812 */
 813int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 814                          splice_actor *actor)
 815{
 816        int ret;
 817
 818        while (pipe->nrbufs) {
 819                struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 820                const struct pipe_buf_operations *ops = buf->ops;
 821
 822                sd->len = buf->len;
 823                if (sd->len > sd->total_len)
 824                        sd->len = sd->total_len;
 825
 826                ret = buf->ops->confirm(pipe, buf);
 827                if (unlikely(ret)) {
 828                        if (ret == -ENODATA)
 829                                ret = 0;
 830                        return ret;
 831                }
 832
 833                ret = actor(pipe, buf, sd);
 834                if (ret <= 0)
 835                        return ret;
 836
 837                buf->offset += ret;
 838                buf->len -= ret;
 839
 840                sd->num_spliced += ret;
 841                sd->len -= ret;
 842                sd->pos += ret;
 843                sd->total_len -= ret;
 844
 845                if (!buf->len) {
 846                        buf->ops = NULL;
 847                        ops->release(pipe, buf);
 848                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 849                        pipe->nrbufs--;
 850                        if (pipe->files)
 851                                sd->need_wakeup = true;
 852                }
 853
 854                if (!sd->total_len)
 855                        return 0;
 856        }
 857
 858        return 1;
 859}
 860EXPORT_SYMBOL(splice_from_pipe_feed);
 861
 862/**
 863 * splice_from_pipe_next - wait for some data to splice from
 864 * @pipe:       pipe to splice from
 865 * @sd:         information about the splice operation
 866 *
 867 * Description:
 868 *    This function will wait for some data and return a positive
 869 *    value (one) if pipe buffers are available.  It will return zero
 870 *    or -errno if no more data needs to be spliced.
 871 */
 872int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 873{
 874        while (!pipe->nrbufs) {
 875                if (!pipe->writers)
 876                        return 0;
 877
 878                if (!pipe->waiting_writers && sd->num_spliced)
 879                        return 0;
 880
 881                if (sd->flags & SPLICE_F_NONBLOCK)
 882                        return -EAGAIN;
 883
 884                if (signal_pending(current))
 885                        return -ERESTARTSYS;
 886
 887                if (sd->need_wakeup) {
 888                        wakeup_pipe_writers(pipe);
 889                        sd->need_wakeup = false;
 890                }
 891
 892                pipe_wait(pipe);
 893        }
 894
 895        return 1;
 896}
 897EXPORT_SYMBOL(splice_from_pipe_next);
 898
 899/**
 900 * splice_from_pipe_begin - start splicing from pipe
 901 * @sd:         information about the splice operation
 902 *
 903 * Description:
 904 *    This function should be called before a loop containing
 905 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 906 *    initialize the necessary fields of @sd.
 907 */
 908void splice_from_pipe_begin(struct splice_desc *sd)
 909{
 910        sd->num_spliced = 0;
 911        sd->need_wakeup = false;
 912}
 913EXPORT_SYMBOL(splice_from_pipe_begin);
 914
 915/**
 916 * splice_from_pipe_end - finish splicing from pipe
 917 * @pipe:       pipe to splice from
 918 * @sd:         information about the splice operation
 919 *
 920 * Description:
 921 *    This function will wake up pipe writers if necessary.  It should
 922 *    be called after a loop containing splice_from_pipe_next() and
 923 *    splice_from_pipe_feed().
 924 */
 925void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 926{
 927        if (sd->need_wakeup)
 928                wakeup_pipe_writers(pipe);
 929}
 930EXPORT_SYMBOL(splice_from_pipe_end);
 931
 932/**
 933 * __splice_from_pipe - splice data from a pipe to given actor
 934 * @pipe:       pipe to splice from
 935 * @sd:         information to @actor
 936 * @actor:      handler that splices the data
 937 *
 938 * Description:
 939 *    This function does little more than loop over the pipe and call
 940 *    @actor to do the actual moving of a single struct pipe_buffer to
 941 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 942 *    pipe_to_user.
 943 *
 944 */
 945ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 946                           splice_actor *actor)
 947{
 948        int ret;
 949
 950        splice_from_pipe_begin(sd);
 951        do {
 952                ret = splice_from_pipe_next(pipe, sd);
 953                if (ret > 0)
 954                        ret = splice_from_pipe_feed(pipe, sd, actor);
 955        } while (ret > 0);
 956        splice_from_pipe_end(pipe, sd);
 957
 958        return sd->num_spliced ? sd->num_spliced : ret;
 959}
 960EXPORT_SYMBOL(__splice_from_pipe);
 961
 962/**
 963 * splice_from_pipe - splice data from a pipe to a file
 964 * @pipe:       pipe to splice from
 965 * @out:        file to splice to
 966 * @ppos:       position in @out
 967 * @len:        how many bytes to splice
 968 * @flags:      splice modifier flags
 969 * @actor:      handler that splices the data
 970 *
 971 * Description:
 972 *    See __splice_from_pipe. This function locks the pipe inode,
 973 *    otherwise it's identical to __splice_from_pipe().
 974 *
 975 */
 976ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 977                         loff_t *ppos, size_t len, unsigned int flags,
 978                         splice_actor *actor)
 979{
 980        ssize_t ret;
 981        struct splice_desc sd = {
 982                .total_len = len,
 983                .flags = flags,
 984                .pos = *ppos,
 985                .u.file = out,
 986        };
 987
 988        pipe_lock(pipe);
 989        ret = __splice_from_pipe(pipe, &sd, actor);
 990        pipe_unlock(pipe);
 991
 992        return ret;
 993}
 994
 995/**
 996 * generic_file_splice_write - splice data from a pipe to a file
 997 * @pipe:       pipe info
 998 * @out:        file to write to
 999 * @ppos:       position in @out
1000 * @len:        number of bytes to splice
1001 * @flags:      splice modifier flags
1002 *
1003 * Description:
1004 *    Will either move or copy pages (determined by @flags options) from
1005 *    the given pipe inode to the given file.
1006 *
1007 */
1008ssize_t
1009generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
1010                          loff_t *ppos, size_t len, unsigned int flags)
1011{
1012        struct address_space *mapping = out->f_mapping;
1013        struct inode *inode = mapping->host;
1014        struct splice_desc sd = {
1015                .total_len = len,
1016                .flags = flags,
1017                .pos = *ppos,
1018                .u.file = out,
1019        };
1020        ssize_t ret;
1021
1022        pipe_lock(pipe);
1023
1024        splice_from_pipe_begin(&sd);
1025        do {
1026                ret = splice_from_pipe_next(pipe, &sd);
1027                if (ret <= 0)
1028                        break;
1029
1030                mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1031                ret = file_remove_suid(out);
1032                if (!ret) {
1033                        ret = file_update_time(out);
1034                        if (!ret)
1035                                ret = splice_from_pipe_feed(pipe, &sd,
1036                                                            pipe_to_file);
1037                }
1038                mutex_unlock(&inode->i_mutex);
1039        } while (ret > 0);
1040        splice_from_pipe_end(pipe, &sd);
1041
1042        pipe_unlock(pipe);
1043
1044        if (sd.num_spliced)
1045                ret = sd.num_spliced;
1046
1047        if (ret > 0) {
1048                int err;
1049
1050                err = generic_write_sync(out, *ppos, ret);
1051                if (err)
1052                        ret = err;
1053                else
1054                        *ppos += ret;
1055                balance_dirty_pages_ratelimited(mapping);
1056        }
1057
1058        return ret;
1059}
1060
1061EXPORT_SYMBOL(generic_file_splice_write);
1062
1063static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1064                          struct splice_desc *sd)
1065{
1066        int ret;
1067        void *data;
1068        loff_t tmp = sd->pos;
1069
1070        data = buf->ops->map(pipe, buf, 0);
1071        ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
1072        buf->ops->unmap(pipe, buf, data);
1073
1074        return ret;
1075}
1076
1077static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1078                                         struct file *out, loff_t *ppos,
1079                                         size_t len, unsigned int flags)
1080{
1081        ssize_t ret;
1082
1083        ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1084        if (ret > 0)
1085                *ppos += ret;
1086
1087        return ret;
1088}
1089
1090/**
1091 * generic_splice_sendpage - splice data from a pipe to a socket
1092 * @pipe:       pipe to splice from
1093 * @out:        socket to write to
1094 * @ppos:       position in @out
1095 * @len:        number of bytes to splice
1096 * @flags:      splice modifier flags
1097 *
1098 * Description:
1099 *    Will send @len bytes from the pipe to a network socket. No data copying
1100 *    is involved.
1101 *
1102 */
1103ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1104                                loff_t *ppos, size_t len, unsigned int flags)
1105{
1106        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1107}
1108
1109EXPORT_SYMBOL(generic_splice_sendpage);
1110
1111/*
1112 * Attempt to initiate a splice from pipe to file.
1113 */
1114static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1115                           loff_t *ppos, size_t len, unsigned int flags)
1116{
1117        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1118                                loff_t *, size_t, unsigned int);
1119
1120        if (out->f_op->splice_write)
1121                splice_write = out->f_op->splice_write;
1122        else
1123                splice_write = default_file_splice_write;
1124
1125        return splice_write(pipe, out, ppos, len, flags);
1126}
1127
1128/*
1129 * Attempt to initiate a splice from a file to a pipe.
1130 */
1131static long do_splice_to(struct file *in, loff_t *ppos,
1132                         struct pipe_inode_info *pipe, size_t len,
1133                         unsigned int flags)
1134{
1135        ssize_t (*splice_read)(struct file *, loff_t *,
1136                               struct pipe_inode_info *, size_t, unsigned int);
1137        int ret;
1138
1139        if (unlikely(!(in->f_mode & FMODE_READ)))
1140                return -EBADF;
1141
1142        ret = rw_verify_area(READ, in, ppos, len);
1143        if (unlikely(ret < 0))
1144                return ret;
1145
1146        if (in->f_op->splice_read)
1147                splice_read = in->f_op->splice_read;
1148        else
1149                splice_read = default_file_splice_read;
1150
1151        return splice_read(in, ppos, pipe, len, flags);
1152}
1153
1154/**
1155 * splice_direct_to_actor - splices data directly between two non-pipes
1156 * @in:         file to splice from
1157 * @sd:         actor information on where to splice to
1158 * @actor:      handles the data splicing
1159 *
1160 * Description:
1161 *    This is a special case helper to splice directly between two
1162 *    points, without requiring an explicit pipe. Internally an allocated
1163 *    pipe is cached in the process, and reused during the lifetime of
1164 *    that process.
1165 *
1166 */
1167ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1168                               splice_direct_actor *actor)
1169{
1170        struct pipe_inode_info *pipe;
1171        long ret, bytes;
1172        umode_t i_mode;
1173        size_t len;
1174        int i, flags;
1175
1176        /*
1177         * We require the input being a regular file, as we don't want to
1178         * randomly drop data for eg socket -> socket splicing. Use the
1179         * piped splicing for that!
1180         */
1181        i_mode = file_inode(in)->i_mode;
1182        if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1183                return -EINVAL;
1184
1185        /*
1186         * neither in nor out is a pipe, setup an internal pipe attached to
1187         * 'out' and transfer the wanted data from 'in' to 'out' through that
1188         */
1189        pipe = current->splice_pipe;
1190        if (unlikely(!pipe)) {
1191                pipe = alloc_pipe_info();
1192                if (!pipe)
1193                        return -ENOMEM;
1194
1195                /*
1196                 * We don't have an immediate reader, but we'll read the stuff
1197                 * out of the pipe right after the splice_to_pipe(). So set
1198                 * PIPE_READERS appropriately.
1199                 */
1200                pipe->readers = 1;
1201
1202                current->splice_pipe = pipe;
1203        }
1204
1205        /*
1206         * Do the splice.
1207         */
1208        ret = 0;
1209        bytes = 0;
1210        len = sd->total_len;
1211        flags = sd->flags;
1212
1213        /*
1214         * Don't block on output, we have to drain the direct pipe.
1215         */
1216        sd->flags &= ~SPLICE_F_NONBLOCK;
1217
1218        while (len) {
1219                size_t read_len;
1220                loff_t pos = sd->pos, prev_pos = pos;
1221
1222                ret = do_splice_to(in, &pos, pipe, len, flags);
1223                if (unlikely(ret <= 0))
1224                        goto out_release;
1225
1226                read_len = ret;
1227                sd->total_len = read_len;
1228
1229                /*
1230                 * NOTE: nonblocking mode only applies to the input. We
1231                 * must not do the output in nonblocking mode as then we
1232                 * could get stuck data in the internal pipe:
1233                 */
1234                ret = actor(pipe, sd);
1235                if (unlikely(ret <= 0)) {
1236                        sd->pos = prev_pos;
1237                        goto out_release;
1238                }
1239
1240                bytes += ret;
1241                len -= ret;
1242                sd->pos = pos;
1243
1244                if (ret < read_len) {
1245                        sd->pos = prev_pos + ret;
1246                        goto out_release;
1247                }
1248        }
1249
1250done:
1251        pipe->nrbufs = pipe->curbuf = 0;
1252        file_accessed(in);
1253        return bytes;
1254
1255out_release:
1256        /*
1257         * If we did an incomplete transfer we must release
1258         * the pipe buffers in question:
1259         */
1260        for (i = 0; i < pipe->buffers; i++) {
1261                struct pipe_buffer *buf = pipe->bufs + i;
1262
1263                if (buf->ops) {
1264                        buf->ops->release(pipe, buf);
1265                        buf->ops = NULL;
1266                }
1267        }
1268
1269        if (!bytes)
1270                bytes = ret;
1271
1272        goto done;
1273}
1274EXPORT_SYMBOL(splice_direct_to_actor);
1275
1276static int direct_splice_actor(struct pipe_inode_info *pipe,
1277                               struct splice_desc *sd)
1278{
1279        struct file *file = sd->u.file;
1280
1281        return do_splice_from(pipe, file, sd->opos, sd->total_len,
1282                              sd->flags);
1283}
1284
1285/**
1286 * do_splice_direct - splices data directly between two files
1287 * @in:         file to splice from
1288 * @ppos:       input file offset
1289 * @out:        file to splice to
1290 * @opos:       output file offset
1291 * @len:        number of bytes to splice
1292 * @flags:      splice modifier flags
1293 *
1294 * Description:
1295 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1296 *    doing it in the application would incur an extra system call
1297 *    (splice in + splice out, as compared to just sendfile()). So this helper
1298 *    can splice directly through a process-private pipe.
1299 *
1300 */
1301long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1302                      loff_t *opos, size_t len, unsigned int flags)
1303{
1304        struct splice_desc sd = {
1305                .len            = len,
1306                .total_len      = len,
1307                .flags          = flags,
1308                .pos            = *ppos,
1309                .u.file         = out,
1310                .opos           = opos,
1311        };
1312        long ret;
1313
1314        if (unlikely(!(out->f_mode & FMODE_WRITE)))
1315                return -EBADF;
1316
1317        if (unlikely(out->f_flags & O_APPEND))
1318                return -EINVAL;
1319
1320        ret = rw_verify_area(WRITE, out, opos, len);
1321        if (unlikely(ret < 0))
1322                return ret;
1323
1324        ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1325        if (ret > 0)
1326                *ppos = sd.pos;
1327
1328        return ret;
1329}
1330
1331static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1332                               struct pipe_inode_info *opipe,
1333                               size_t len, unsigned int flags);
1334
1335/*
1336 * Determine where to splice to/from.
1337 */
1338static long do_splice(struct file *in, loff_t __user *off_in,
1339                      struct file *out, loff_t __user *off_out,
1340                      size_t len, unsigned int flags)
1341{
1342        struct pipe_inode_info *ipipe;
1343        struct pipe_inode_info *opipe;
1344        loff_t offset;
1345        long ret;
1346
1347        ipipe = get_pipe_info(in);
1348        opipe = get_pipe_info(out);
1349
1350        if (ipipe && opipe) {
1351                if (off_in || off_out)
1352                        return -ESPIPE;
1353
1354                if (!(in->f_mode & FMODE_READ))
1355                        return -EBADF;
1356
1357                if (!(out->f_mode & FMODE_WRITE))
1358                        return -EBADF;
1359
1360                /* Splicing to self would be fun, but... */
1361                if (ipipe == opipe)
1362                        return -EINVAL;
1363
1364                return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1365        }
1366
1367        if (ipipe) {
1368                if (off_in)
1369                        return -ESPIPE;
1370                if (off_out) {
1371                        if (!(out->f_mode & FMODE_PWRITE))
1372                                return -EINVAL;
1373                        if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1374                                return -EFAULT;
1375                } else {
1376                        offset = out->f_pos;
1377                }
1378
1379                if (unlikely(!(out->f_mode & FMODE_WRITE)))
1380                        return -EBADF;
1381
1382                if (unlikely(out->f_flags & O_APPEND))
1383                        return -EINVAL;
1384
1385                ret = rw_verify_area(WRITE, out, &offset, len);
1386                if (unlikely(ret < 0))
1387                        return ret;
1388
1389                file_start_write(out);
1390                ret = do_splice_from(ipipe, out, &offset, len, flags);
1391                file_end_write(out);
1392
1393                if (!off_out)
1394                        out->f_pos = offset;
1395                else if (copy_to_user(off_out, &offset, sizeof(loff_t)))
1396                        ret = -EFAULT;
1397
1398                return ret;
1399        }
1400
1401        if (opipe) {
1402                if (off_out)
1403                        return -ESPIPE;
1404                if (off_in) {
1405                        if (!(in->f_mode & FMODE_PREAD))
1406                                return -EINVAL;
1407                        if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1408                                return -EFAULT;
1409                } else {
1410                        offset = in->f_pos;
1411                }
1412
1413                ret = do_splice_to(in, &offset, opipe, len, flags);
1414
1415                if (!off_in)
1416                        in->f_pos = offset;
1417                else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
1418                        ret = -EFAULT;
1419
1420                return ret;
1421        }
1422
1423        return -EINVAL;
1424}
1425
1426/*
1427 * Map an iov into an array of pages and offset/length tupples. With the
1428 * partial_page structure, we can map several non-contiguous ranges into
1429 * our ones pages[] map instead of splitting that operation into pieces.
1430 * Could easily be exported as a generic helper for other users, in which
1431 * case one would probably want to add a 'max_nr_pages' parameter as well.
1432 */
1433static int get_iovec_page_array(const struct iovec __user *iov,
1434                                unsigned int nr_vecs, struct page **pages,
1435                                struct partial_page *partial, bool aligned,
1436                                unsigned int pipe_buffers)
1437{
1438        int buffers = 0, error = 0;
1439
1440        while (nr_vecs) {
1441                unsigned long off, npages;
1442                struct iovec entry;
1443                void __user *base;
1444                size_t len;
1445                int i;
1446
1447                error = -EFAULT;
1448                if (copy_from_user(&entry, iov, sizeof(entry)))
1449                        break;
1450
1451                base = entry.iov_base;
1452                len = entry.iov_len;
1453
1454                /*
1455                 * Sanity check this iovec. 0 read succeeds.
1456                 */
1457                error = 0;
1458                if (unlikely(!len))
1459                        break;
1460                error = -EFAULT;
1461                if (!access_ok(VERIFY_READ, base, len))
1462                        break;
1463
1464                /*
1465                 * Get this base offset and number of pages, then map
1466                 * in the user pages.
1467                 */
1468                off = (unsigned long) base & ~PAGE_MASK;
1469
1470                /*
1471                 * If asked for alignment, the offset must be zero and the
1472                 * length a multiple of the PAGE_SIZE.
1473                 */
1474                error = -EINVAL;
1475                if (aligned && (off || len & ~PAGE_MASK))
1476                        break;
1477
1478                npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1479                if (npages > pipe_buffers - buffers)
1480                        npages = pipe_buffers - buffers;
1481
1482                error = get_user_pages_fast((unsigned long)base, npages,
1483                                        0, &pages[buffers]);
1484
1485                if (unlikely(error <= 0))
1486                        break;
1487
1488                /*
1489                 * Fill this contiguous range into the partial page map.
1490                 */
1491                for (i = 0; i < error; i++) {
1492                        const int plen = min_t(size_t, len, PAGE_SIZE - off);
1493
1494                        partial[buffers].offset = off;
1495                        partial[buffers].len = plen;
1496
1497                        off = 0;
1498                        len -= plen;
1499                        buffers++;
1500                }
1501
1502                /*
1503                 * We didn't complete this iov, stop here since it probably
1504                 * means we have to move some of this into a pipe to
1505                 * be able to continue.
1506                 */
1507                if (len)
1508                        break;
1509
1510                /*
1511                 * Don't continue if we mapped fewer pages than we asked for,
1512                 * or if we mapped the max number of pages that we have
1513                 * room for.
1514                 */
1515                if (error < npages || buffers == pipe_buffers)
1516                        break;
1517
1518                nr_vecs--;
1519                iov++;
1520        }
1521
1522        if (buffers)
1523                return buffers;
1524
1525        return error;
1526}
1527
1528static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1529                        struct splice_desc *sd)
1530{
1531        char *src;
1532        int ret;
1533
1534        /*
1535         * See if we can use the atomic maps, by prefaulting in the
1536         * pages and doing an atomic copy
1537         */
1538        if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1539                src = buf->ops->map(pipe, buf, 1);
1540                ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1541                                                        sd->len);
1542                buf->ops->unmap(pipe, buf, src);
1543                if (!ret) {
1544                        ret = sd->len;
1545                        goto out;
1546                }
1547        }
1548
1549        /*
1550         * No dice, use slow non-atomic map and copy
1551         */
1552        src = buf->ops->map(pipe, buf, 0);
1553
1554        ret = sd->len;
1555        if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1556                ret = -EFAULT;
1557
1558        buf->ops->unmap(pipe, buf, src);
1559out:
1560        if (ret > 0)
1561                sd->u.userptr += ret;
1562        return ret;
1563}
1564
1565/*
1566 * For lack of a better implementation, implement vmsplice() to userspace
1567 * as a simple copy of the pipes pages to the user iov.
1568 */
1569static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1570                             unsigned long nr_segs, unsigned int flags)
1571{
1572        struct pipe_inode_info *pipe;
1573        struct splice_desc sd;
1574        ssize_t size;
1575        int error;
1576        long ret;
1577
1578        pipe = get_pipe_info(file);
1579        if (!pipe)
1580                return -EBADF;
1581
1582        pipe_lock(pipe);
1583
1584        error = ret = 0;
1585        while (nr_segs) {
1586                void __user *base;
1587                size_t len;
1588
1589                /*
1590                 * Get user address base and length for this iovec.
1591                 */
1592                error = get_user(base, &iov->iov_base);
1593                if (unlikely(error))
1594                        break;
1595                error = get_user(len, &iov->iov_len);
1596                if (unlikely(error))
1597                        break;
1598
1599                /*
1600                 * Sanity check this iovec. 0 read succeeds.
1601                 */
1602                if (unlikely(!len))
1603                        break;
1604                if (unlikely(!base)) {
1605                        error = -EFAULT;
1606                        break;
1607                }
1608
1609                if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1610                        error = -EFAULT;
1611                        break;
1612                }
1613
1614                sd.len = 0;
1615                sd.total_len = len;
1616                sd.flags = flags;
1617                sd.u.userptr = base;
1618                sd.pos = 0;
1619
1620                size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1621                if (size < 0) {
1622                        if (!ret)
1623                                ret = size;
1624
1625                        break;
1626                }
1627
1628                ret += size;
1629
1630                if (size < len)
1631                        break;
1632
1633                nr_segs--;
1634                iov++;
1635        }
1636
1637        pipe_unlock(pipe);
1638
1639        if (!ret)
1640                ret = error;
1641
1642        return ret;
1643}
1644
1645/*
1646 * vmsplice splices a user address range into a pipe. It can be thought of
1647 * as splice-from-memory, where the regular splice is splice-from-file (or
1648 * to file). In both cases the output is a pipe, naturally.
1649 */
1650static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1651                             unsigned long nr_segs, unsigned int flags)
1652{
1653        struct pipe_inode_info *pipe;
1654        struct page *pages[PIPE_DEF_BUFFERS];
1655        struct partial_page partial[PIPE_DEF_BUFFERS];
1656        struct splice_pipe_desc spd = {
1657                .pages = pages,
1658                .partial = partial,
1659                .nr_pages_max = PIPE_DEF_BUFFERS,
1660                .flags = flags,
1661                .ops = &user_page_pipe_buf_ops,
1662                .spd_release = spd_release_page,
1663        };
1664        long ret;
1665
1666        pipe = get_pipe_info(file);
1667        if (!pipe)
1668                return -EBADF;
1669
1670        if (splice_grow_spd(pipe, &spd))
1671                return -ENOMEM;
1672
1673        spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1674                                            spd.partial, false,
1675                                            spd.nr_pages_max);
1676        if (spd.nr_pages <= 0)
1677                ret = spd.nr_pages;
1678        else
1679                ret = splice_to_pipe(pipe, &spd);
1680
1681        splice_shrink_spd(&spd);
1682        return ret;
1683}
1684
1685/*
1686 * Note that vmsplice only really supports true splicing _from_ user memory
1687 * to a pipe, not the other way around. Splicing from user memory is a simple
1688 * operation that can be supported without any funky alignment restrictions
1689 * or nasty vm tricks. We simply map in the user memory and fill them into
1690 * a pipe. The reverse isn't quite as easy, though. There are two possible
1691 * solutions for that:
1692 *
1693 *      - memcpy() the data internally, at which point we might as well just
1694 *        do a regular read() on the buffer anyway.
1695 *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1696 *        has restriction limitations on both ends of the pipe).
1697 *
1698 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1699 *
1700 */
1701SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1702                unsigned long, nr_segs, unsigned int, flags)
1703{
1704        struct fd f;
1705        long error;
1706
1707        if (unlikely(nr_segs > UIO_MAXIOV))
1708                return -EINVAL;
1709        else if (unlikely(!nr_segs))
1710                return 0;
1711
1712        error = -EBADF;
1713        f = fdget(fd);
1714        if (f.file) {
1715                if (f.file->f_mode & FMODE_WRITE)
1716                        error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
1717                else if (f.file->f_mode & FMODE_READ)
1718                        error = vmsplice_to_user(f.file, iov, nr_segs, flags);
1719
1720                fdput(f);
1721        }
1722
1723        return error;
1724}
1725
1726#ifdef CONFIG_COMPAT
1727COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
1728                    unsigned int, nr_segs, unsigned int, flags)
1729{
1730        unsigned i;
1731        struct iovec __user *iov;
1732        if (nr_segs > UIO_MAXIOV)
1733                return -EINVAL;
1734        iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
1735        for (i = 0; i < nr_segs; i++) {
1736                struct compat_iovec v;
1737                if (get_user(v.iov_base, &iov32[i].iov_base) ||
1738                    get_user(v.iov_len, &iov32[i].iov_len) ||
1739                    put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
1740                    put_user(v.iov_len, &iov[i].iov_len))
1741                        return -EFAULT;
1742        }
1743        return sys_vmsplice(fd, iov, nr_segs, flags);
1744}
1745#endif
1746
1747SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1748                int, fd_out, loff_t __user *, off_out,
1749                size_t, len, unsigned int, flags)
1750{
1751        struct fd in, out;
1752        long error;
1753
1754        if (unlikely(!len))
1755                return 0;
1756
1757        error = -EBADF;
1758        in = fdget(fd_in);
1759        if (in.file) {
1760                if (in.file->f_mode & FMODE_READ) {
1761                        out = fdget(fd_out);
1762                        if (out.file) {
1763                                if (out.file->f_mode & FMODE_WRITE)
1764                                        error = do_splice(in.file, off_in,
1765                                                          out.file, off_out,
1766                                                          len, flags);
1767                                fdput(out);
1768                        }
1769                }
1770                fdput(in);
1771        }
1772        return error;
1773}
1774
1775/*
1776 * Make sure there's data to read. Wait for input if we can, otherwise
1777 * return an appropriate error.
1778 */
1779static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1780{
1781        int ret;
1782
1783        /*
1784         * Check ->nrbufs without the inode lock first. This function
1785         * is speculative anyways, so missing one is ok.
1786         */
1787        if (pipe->nrbufs)
1788                return 0;
1789
1790        ret = 0;
1791        pipe_lock(pipe);
1792
1793        while (!pipe->nrbufs) {
1794                if (signal_pending(current)) {
1795                        ret = -ERESTARTSYS;
1796                        break;
1797                }
1798                if (!pipe->writers)
1799                        break;
1800                if (!pipe->waiting_writers) {
1801                        if (flags & SPLICE_F_NONBLOCK) {
1802                                ret = -EAGAIN;
1803                                break;
1804                        }
1805                }
1806                pipe_wait(pipe);
1807        }
1808
1809        pipe_unlock(pipe);
1810        return ret;
1811}
1812
1813/*
1814 * Make sure there's writeable room. Wait for room if we can, otherwise
1815 * return an appropriate error.
1816 */
1817static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1818{
1819        int ret;
1820
1821        /*
1822         * Check ->nrbufs without the inode lock first. This function
1823         * is speculative anyways, so missing one is ok.
1824         */
1825        if (pipe->nrbufs < pipe->buffers)
1826                return 0;
1827
1828        ret = 0;
1829        pipe_lock(pipe);
1830
1831        while (pipe->nrbufs >= pipe->buffers) {
1832                if (!pipe->readers) {
1833                        send_sig(SIGPIPE, current, 0);
1834                        ret = -EPIPE;
1835                        break;
1836                }
1837                if (flags & SPLICE_F_NONBLOCK) {
1838                        ret = -EAGAIN;
1839                        break;
1840                }
1841                if (signal_pending(current)) {
1842                        ret = -ERESTARTSYS;
1843                        break;
1844                }
1845                pipe->waiting_writers++;
1846                pipe_wait(pipe);
1847                pipe->waiting_writers--;
1848        }
1849
1850        pipe_unlock(pipe);
1851        return ret;
1852}
1853
1854/*
1855 * Splice contents of ipipe to opipe.
1856 */
1857static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1858                               struct pipe_inode_info *opipe,
1859                               size_t len, unsigned int flags)
1860{
1861        struct pipe_buffer *ibuf, *obuf;
1862        int ret = 0, nbuf;
1863        bool input_wakeup = false;
1864
1865
1866retry:
1867        ret = ipipe_prep(ipipe, flags);
1868        if (ret)
1869                return ret;
1870
1871        ret = opipe_prep(opipe, flags);
1872        if (ret)
1873                return ret;
1874
1875        /*
1876         * Potential ABBA deadlock, work around it by ordering lock
1877         * grabbing by pipe info address. Otherwise two different processes
1878         * could deadlock (one doing tee from A -> B, the other from B -> A).
1879         */
1880        pipe_double_lock(ipipe, opipe);
1881
1882        do {
1883                if (!opipe->readers) {
1884                        send_sig(SIGPIPE, current, 0);
1885                        if (!ret)
1886                                ret = -EPIPE;
1887                        break;
1888                }
1889
1890                if (!ipipe->nrbufs && !ipipe->writers)
1891                        break;
1892
1893                /*
1894                 * Cannot make any progress, because either the input
1895                 * pipe is empty or the output pipe is full.
1896                 */
1897                if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1898                        /* Already processed some buffers, break */
1899                        if (ret)
1900                                break;
1901
1902                        if (flags & SPLICE_F_NONBLOCK) {
1903                                ret = -EAGAIN;
1904                                break;
1905                        }
1906
1907                        /*
1908                         * We raced with another reader/writer and haven't
1909                         * managed to process any buffers.  A zero return
1910                         * value means EOF, so retry instead.
1911                         */
1912                        pipe_unlock(ipipe);
1913                        pipe_unlock(opipe);
1914                        goto retry;
1915                }
1916
1917                ibuf = ipipe->bufs + ipipe->curbuf;
1918                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1919                obuf = opipe->bufs + nbuf;
1920
1921                if (len >= ibuf->len) {
1922                        /*
1923                         * Simply move the whole buffer from ipipe to opipe
1924                         */
1925                        *obuf = *ibuf;
1926                        ibuf->ops = NULL;
1927                        opipe->nrbufs++;
1928                        ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1929                        ipipe->nrbufs--;
1930                        input_wakeup = true;
1931                } else {
1932                        /*
1933                         * Get a reference to this pipe buffer,
1934                         * so we can copy the contents over.
1935                         */
1936                        ibuf->ops->get(ipipe, ibuf);
1937                        *obuf = *ibuf;
1938
1939                        /*
1940                         * Don't inherit the gift flag, we need to
1941                         * prevent multiple steals of this page.
1942                         */
1943                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1944
1945                        obuf->len = len;
1946                        opipe->nrbufs++;
1947                        ibuf->offset += obuf->len;
1948                        ibuf->len -= obuf->len;
1949                }
1950                ret += obuf->len;
1951                len -= obuf->len;
1952        } while (len);
1953
1954        pipe_unlock(ipipe);
1955        pipe_unlock(opipe);
1956
1957        /*
1958         * If we put data in the output pipe, wakeup any potential readers.
1959         */
1960        if (ret > 0)
1961                wakeup_pipe_readers(opipe);
1962
1963        if (input_wakeup)
1964                wakeup_pipe_writers(ipipe);
1965
1966        return ret;
1967}
1968
1969/*
1970 * Link contents of ipipe to opipe.
1971 */
1972static int link_pipe(struct pipe_inode_info *ipipe,
1973                     struct pipe_inode_info *opipe,
1974                     size_t len, unsigned int flags)
1975{
1976        struct pipe_buffer *ibuf, *obuf;
1977        int ret = 0, i = 0, nbuf;
1978
1979        /*
1980         * Potential ABBA deadlock, work around it by ordering lock
1981         * grabbing by pipe info address. Otherwise two different processes
1982         * could deadlock (one doing tee from A -> B, the other from B -> A).
1983         */
1984        pipe_double_lock(ipipe, opipe);
1985
1986        do {
1987                if (!opipe->readers) {
1988                        send_sig(SIGPIPE, current, 0);
1989                        if (!ret)
1990                                ret = -EPIPE;
1991                        break;
1992                }
1993
1994                /*
1995                 * If we have iterated all input buffers or ran out of
1996                 * output room, break.
1997                 */
1998                if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1999                        break;
2000
2001                ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
2002                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
2003
2004                /*
2005                 * Get a reference to this pipe buffer,
2006                 * so we can copy the contents over.
2007                 */
2008                ibuf->ops->get(ipipe, ibuf);
2009
2010                obuf = opipe->bufs + nbuf;
2011                *obuf = *ibuf;
2012
2013                /*
2014                 * Don't inherit the gift flag, we need to
2015                 * prevent multiple steals of this page.
2016                 */
2017                obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
2018
2019                if (obuf->len > len)
2020                        obuf->len = len;
2021
2022                opipe->nrbufs++;
2023                ret += obuf->len;
2024                len -= obuf->len;
2025                i++;
2026        } while (len);
2027
2028        /*
2029         * return EAGAIN if we have the potential of some data in the
2030         * future, otherwise just return 0
2031         */
2032        if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
2033                ret = -EAGAIN;
2034
2035        pipe_unlock(ipipe);
2036        pipe_unlock(opipe);
2037
2038        /*
2039         * If we put data in the output pipe, wakeup any potential readers.
2040         */
2041        if (ret > 0)
2042                wakeup_pipe_readers(opipe);
2043
2044        return ret;
2045}
2046
2047/*
2048 * This is a tee(1) implementation that works on pipes. It doesn't copy
2049 * any data, it simply references the 'in' pages on the 'out' pipe.
2050 * The 'flags' used are the SPLICE_F_* variants, currently the only
2051 * applicable one is SPLICE_F_NONBLOCK.
2052 */
2053static long do_tee(struct file *in, struct file *out, size_t len,
2054                   unsigned int flags)
2055{
2056        struct pipe_inode_info *ipipe = get_pipe_info(in);
2057        struct pipe_inode_info *opipe = get_pipe_info(out);
2058        int ret = -EINVAL;
2059
2060        /*
2061         * Duplicate the contents of ipipe to opipe without actually
2062         * copying the data.
2063         */
2064        if (ipipe && opipe && ipipe != opipe) {
2065                /*
2066                 * Keep going, unless we encounter an error. The ipipe/opipe
2067                 * ordering doesn't really matter.
2068                 */
2069                ret = ipipe_prep(ipipe, flags);
2070                if (!ret) {
2071                        ret = opipe_prep(opipe, flags);
2072                        if (!ret)
2073                                ret = link_pipe(ipipe, opipe, len, flags);
2074                }
2075        }
2076
2077        return ret;
2078}
2079
2080SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2081{
2082        struct fd in;
2083        int error;
2084
2085        if (unlikely(!len))
2086                return 0;
2087
2088        error = -EBADF;
2089        in = fdget(fdin);
2090        if (in.file) {
2091                if (in.file->f_mode & FMODE_READ) {
2092                        struct fd out = fdget(fdout);
2093                        if (out.file) {
2094                                if (out.file->f_mode & FMODE_WRITE)
2095                                        error = do_tee(in.file, out.file,
2096                                                        len, flags);
2097                                fdput(out);
2098                        }
2099                }
2100                fdput(in);
2101        }
2102
2103        return error;
2104}
2105