/* * "splice": joining two ropes together by interweaving their strands. * * This is the "extended pipe" functionality, where a pipe is used as * an arbitrary in-memory buffer. Think of a pipe as a small kernel * buffer that you can use to transfer data from one end to the other. * * The traditional unix read/write is extended with a "splice()" operation * that transfers data buffers to or from a pipe buffer. * * Named by Larry McVoy, original implementation from Linus, extended by * Jens to support splicing to files, network, direct splicing, etc and * fixing lots of bugs. * * Copyright (C) 2005-2006 Jens Axboe * Copyright (C) 2005-2006 Linus Torvalds * Copyright (C) 2006 Ingo Molnar * */ #include #include #include #include #include #include #include #include #include #include #include struct partial_page { unsigned int offset; unsigned int len; }; /* * Passed to splice_to_pipe */ struct splice_pipe_desc { struct page **pages; /* page map */ struct partial_page *partial; /* pages[] may not be contig */ int nr_pages; /* number of pages in map */ unsigned int flags; /* splice flags */ struct pipe_buf_operations *ops;/* ops associated with output pipe */ }; /* * Attempt to steal a page from a pipe buffer. This should perhaps go into * a vm helper function, it's already simplified quite a bit by the * addition of remove_mapping(). If success is returned, the caller may * attempt to reuse this page for another destination. */ static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct page *page = buf->page; struct address_space *mapping; lock_page(page); mapping = page_mapping(page); if (mapping) { WARN_ON(!PageUptodate(page)); /* * At least for ext2 with nobh option, we need to wait on * writeback completing on this page, since we'll remove it * from the pagecache. Otherwise truncate wont wait on the * page, allowing the disk blocks to be reused by someone else * before we actually wrote our data to them. fs corruption * ensues. */ wait_on_page_writeback(page); if (PagePrivate(page)) try_to_release_page(page, mapping_gfp_mask(mapping)); /* * If we succeeded in removing the mapping, set LRU flag * and return good. */ if (remove_mapping(mapping, page)) { buf->flags |= PIPE_BUF_FLAG_LRU; return 0; } } /* * Raced with truncate or failed to remove page from current * address space, unlock and return failure. */ unlock_page(page); return 1; } static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { page_cache_release(buf->page); buf->flags &= ~PIPE_BUF_FLAG_LRU; } static int page_cache_pipe_buf_pin(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct page *page = buf->page; int err; if (!PageUptodate(page)) { lock_page(page); /* * Page got truncated/unhashed. This will cause a 0-byte * splice, if this is the first page. */ if (!page->mapping) { err = -ENODATA; goto error; } /* * Uh oh, read-error from disk. */ if (!PageUptodate(page)) { err = -EIO; goto error; } /* * Page is ok afterall, we are done. */ unlock_page(page); } return 0; error: unlock_page(page); return err; } static struct pipe_buf_operations page_cache_pipe_buf_ops = { .can_merge = 0, .map = generic_pipe_buf_map, .unmap = generic_pipe_buf_unmap, .pin = page_cache_pipe_buf_pin, .release = page_cache_pipe_buf_release, .steal = page_cache_pipe_buf_steal, .get = generic_pipe_buf_get, }; static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { if (!(buf->flags & PIPE_BUF_FLAG_GIFT)) return 1; buf->flags |= PIPE_BUF_FLAG_LRU; return generic_pipe_buf_steal(pipe, buf); } static struct pipe_buf_operations user_page_pipe_buf_ops = { .can_merge = 0, .map = generic_pipe_buf_map, .unmap = generic_pipe_buf_unmap, .pin = generic_pipe_buf_pin, .release = page_cache_pipe_buf_release, .steal = user_page_pipe_buf_steal, .get = generic_pipe_buf_get, }; /* * Pipe output worker. This sets up our pipe format with the page cache * pipe buffer operations. Otherwise very similar to the regular pipe_writev(). */ static ssize_t splice_to_pipe(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) { int ret, do_wakeup, page_nr; ret = 0; do_wakeup = 0; page_nr = 0; if (pipe->inode) mutex_lock(&pipe->inode->i_mutex); for (;;) { if (!pipe->readers) { send_sig(SIGPIPE, current, 0); if (!ret) ret = -EPIPE; break; } if (pipe->nrbufs < PIPE_BUFFERS) { int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1); struct pipe_buffer *buf = pipe->bufs + newbuf; buf->page = spd->pages[page_nr]; buf->offset = spd->partial[page_nr].offset; buf->len = spd->partial[page_nr].len; buf->ops = spd->ops; if (spd->flags & SPLICE_F_GIFT) buf->flags |= PIPE_BUF_FLAG_GIFT; pipe->nrbufs++; page_nr++; ret += buf->len; if (pipe->inode) do_wakeup = 1; if (!--spd->nr_pages) break; if (pipe->nrbufs < PIPE_BUFFERS) continue; break; } if (spd->flags & SPLICE_F_NONBLOCK) { if (!ret) ret = -EAGAIN; break; } if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } if (do_wakeup) { smp_mb(); if (waitqueue_active(&pipe->wait)) wake_up_interruptible_sync(&pipe->wait); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); do_wakeup = 0; } pipe->waiting_writers++; pipe_wait(pipe); pipe->waiting_writers--; } if (pipe->inode) mutex_unlock(&pipe->inode->i_mutex); if (do_wakeup) { smp_mb(); if (waitqueue_active(&pipe->wait)) wake_up_interruptible(&pipe->wait); kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); } while (page_nr < spd->nr_pages) page_cache_release(spd->pages[page_nr++]); return ret; } static int __generic_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { struct address_space *mapping = in->f_mapping; unsigned int loff, nr_pages; struct page *pages[PIPE_BUFFERS]; struct partial_page partial[PIPE_BUFFERS]; struct page *page; pgoff_t index, end_index; loff_t isize; size_t total_len; int error, page_nr; struct splice_pipe_desc spd = { .pages = pages, .partial = partial, .flags = flags, .ops = &page_cache_pipe_buf_ops, }; index = *ppos >> PAGE_CACHE_SHIFT; loff = *ppos & ~PAGE_CACHE_MASK; nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; if (nr_pages > PIPE_BUFFERS) nr_pages = PIPE_BUFFERS; /* * Initiate read-ahead on this page range. however, don't call into * read-ahead if this is a non-zero offset (we are likely doing small * chunk splice and the page is already there) for a single page. */ if (!loff || nr_pages > 1) page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages); /* * Now fill in the holes: */ error = 0; total_len = 0; /* * Lookup the (hopefully) full range of pages we need. */ spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages); /* * If find_get_pages_contig() returned fewer pages than we needed, * allocate the rest. */ index += spd.nr_pages; while (spd.nr_pages < nr_pages) { /* * Page could be there, find_get_pages_contig() breaks on * the first hole. */ page = find_get_page(mapping, index); if (!page) { /* * Make sure the read-ahead engine is notified * about this failure. */ handle_ra_miss(mapping, &in->f_ra, index); /* * page didn't exist, allocate one. */ page = page_cache_alloc_cold(mapping); if (!page) break; error = add_to_page_cache_lru(page, mapping, index, mapping_gfp_mask(mapping)); if (unlikely(error)) { page_cache_release(page); if (error == -EEXIST) continue; break; } /* * add_to_page_cache() locks the page, unlock it * to avoid convoluting the logic below even more. */ unlock_page(page); } pages[spd.nr_pages++] = page; index++; } /* * Now loop over the map and see if we need to start IO on any * pages, fill in the partial map, etc. */ index = *ppos >> PAGE_CACHE_SHIFT; nr_pages = spd.nr_pages; spd.nr_pages = 0; for (page_nr = 0; page_nr < nr_pages; page_nr++) { unsigned int this_len; if (!len) break; /* * this_len is the max we'll use from this page */ this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); page = pages[page_nr]; /* * If the page isn't uptodate, we may need to start io on it */ if (!PageUptodate(page)) { /* * If in nonblock mode then dont block on waiting * for an in-flight io page */ if (flags & SPLICE_F_NONBLOCK) break; lock_page(page); /* * page was truncated, stop here. if this isn't the * first page, we'll just complete what we already * added */ if (!page->mapping) { unlock_page(page); break; } /* * page was already under io and is now done, great */ if (PageUptodate(page)) { unlock_page(page); goto fill_it; } /* * need to read in the page */ error = mapping->a_ops->readpage(in, page); if (unlikely(error)) { /* * We really should re-lookup the page here, * but it complicates things a lot. Instead * lets just do what we already stored, and * we'll get it the next time we are called. */ if (error == AOP_TRUNCATED_PAGE) error = 0; break; } /* * i_size must be checked after ->readpage(). */ isize = i_size_read(mapping->host); end_index = (isize - 1) >> PAGE_CACHE_SHIFT; if (unlikely(!isize || index > end_index)) break; /* * if this is the last page, see if we need to shrink * the length and stop */ if (end_index == index) { loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK); if (total_len + loff > isize) break; /* * force quit after adding this page */ len = this_len; this_len = min(this_len, loff); loff = 0; } } fill_it: partial[page_nr].offset = loff; partial[page_nr].len = this_len; len -= this_len; total_len += this_len; loff = 0; spd.nr_pages++; index++; } /* * Release any pages at the end, if we quit early. 'i' is how far * we got, 'nr_pages' is how many pages are in the map. */ while (page_nr < nr_pages) page_cache_release(pages[page_nr++]); if (spd.nr_pages) return splice_to_pipe(pipe, &spd); return error; } /** * generic_file_splice_read - splice data from file to a pipe * @in: file to splice from * @pipe: pipe to splice to * @len: number of bytes to splice * @flags: splice modifier flags * * Will read pages from given file and fill them into a pipe. */ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { ssize_t spliced; int ret; ret = 0; spliced = 0; while (len) { ret = __generic_file_splice_read(in, ppos, pipe, len, flags); if (ret < 0) break; else if (!ret) { if (spliced) break; if (flags & SPLICE_F_NONBLOCK) { ret = -EAGAIN; break; } } *ppos += ret; len -= ret; spliced += ret; } if (spliced) return spliced; return ret; } EXPORT_SYMBOL(generic_file_splice_read); /* * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos' * using sendpage(). Return the number of bytes sent. */ static int pipe_to_sendpage(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct splice_desc *sd) { struct file *file = sd->file; loff_t pos = sd->pos; int ret, more; ret = buf->ops->pin(pipe, buf); if (!ret) { more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len; ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len, &pos, more); } return ret; } /* * This is a little more tricky than the file -> pipe splicing. There are * basically three cases: * * - Destination page already exists in the address space and there * are users of it. For that case we have no other option that * copying the data. Tough luck. * - Destination page already exists in the address space, but there * are no users of it. Make sure it's uptodate, then drop it. Fall * through to last case. * - Destination page does not exist, we can add the pipe page to * the page cache and avoid the copy. * * If asked to move pages to the output file (SPLICE_F_MOVE is set in * sd->flags), we attempt to migrate pages from the pipe to the output * file address space page cache. This is possible if no one else has * the pipe page referenced outside of the pipe and page cache. If * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create * a new page in the output file page cache and fill/dirty that. */ static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct splice_desc *sd) { struct file *file = sd->file; struct address_space *mapping = file->f_mapping; gfp_t gfp_mask = mapping_gfp_mask(mapping); unsigned int offset, this_len; struct page *page; pgoff_t index; int ret; /* * make sure the data in this buffer is uptodate */ ret = buf->ops->pin(pipe, buf); if (unlikely(ret)) return ret; index = sd->pos >> PAGE_CACHE_SHIFT; offset = sd->pos & ~PAGE_CACHE_MASK; this_len = sd->len; if (this_len + offset > PAGE_CACHE_SIZE) this_len = PAGE_CACHE_SIZE - offset; /* * Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full * page. */ if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) { /* * If steal succeeds, buf->page is now pruned from the * pagecache and we can reuse it. The page will also be * locked on successful return. */ if (buf->ops->steal(pipe, buf)) goto find_page; page = buf->page; if (add_to_page_cache(page, mapping, index, gfp_mask)) { unlock_page(page); goto find_page; } page_cache_get(page); if (!(buf->flags & PIPE_BUF_FLAG_LRU)) lru_cache_add(page); } else { find_page: page = find_lock_page(mapping, index); if (!page) { ret = -ENOMEM; page = page_cache_alloc_cold(mapping); if (unlikely(!page)) goto out_ret; /* * This will also lock the page */ ret = add_to_page_cache_lru(page, mapping, index, gfp_mask); if (unlikely(ret)) goto out; } /* * We get here with the page locked. If the page is also * uptodate, we don't need to do more. If it isn't, we * may need to bring it in if we are not going to overwrite * the full page. */ if (!PageUptodate(page)) { if (this_len < PAGE_CACHE_SIZE) { ret = mapping->a_ops->readpage(file, page); if (unlikely(ret)) goto out; lock_page(page); if (!PageUptodate(page)) { /* * Page got invalidated, repeat. */ if (!page->mapping) { unlock_page(page); page_cache_release(page); goto find_page; } ret = -EIO; goto out; } } else SetPageUptodate(page); } } ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len); if (unlikely(ret)) { loff_t isize = i_size_read(mapping->host); if (ret != AOP_TRUNCATED_PAGE) unlock_page(page); page_cache_release(page); if (ret == AOP_TRUNCATED_PAGE) goto find_page; /* * prepare_write() may have instantiated a few blocks * outside i_size. Trim these off again. */ if (sd->pos + this_len > isize) vmtruncate(mapping->host, isize); goto out_ret; } if (buf->page != page) { /* * Careful, ->map() uses KM_USER0! */ char *src = buf->ops->map(pipe, buf, 1); char *dst = kmap_atomic(page, KM_USER1); memcpy(dst + offset, src + buf->offset, this_len); flush_dcache_page(page); kunmap_atomic(dst, KM_USER1); buf->ops->unmap(pipe, buf, src); } ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len); if (!ret) { /* * Return the number of bytes written and mark page as * accessed, we are now done! */ ret = this_len; mark_page_accessed(page); balance_dirty_pages_ratelimited(mapping); } else if (ret == AOP_TRUNCATED_PAGE) { page_cache_release(page); goto find_page; } out: page_cache_release(page); unlock_page(page); out_ret: return ret; } /* * Pipe input worker. Most of this logic works like a regular pipe, the * key here is the 'actor' worker passed in that actually moves the data * to the wanted destination. See pipe_to_file/pipe_to_sendpage above. */ static ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags, splice_actor *actor) { int ret, do_wakeup, err; struct splice_desc sd; ret = 0; do_wakeup = 0; sd.total_len = len; sd.flags = flags; sd.file = out; sd.pos = *ppos; for (;;) { if (pipe->nrbufs) { struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; struct pipe_buf_operations *ops = buf->ops; sd.len = buf->len; if (sd.len > sd.total_len) sd.len = sd.total_len; err = actor(pipe, buf, &sd); if (err <= 0) { if (!ret && err != -ENODATA) ret = err; break; } ret += err; buf->offset += err; buf->len -= err; sd.len -= err; sd.pos += err; sd.total_len -= err; if (sd.len) continue; if (!buf->len) { buf->ops = NULL; ops->release(pipe, buf); pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1); pipe->nrbufs--; if (pipe->inode) do_wakeup = 1; } if (!sd.total_len) break; } if (pipe->nrbufs) continue; if (!pipe->writers) break; if (!pipe->waiting_writers) { if (ret) break; } if (flags & SPLICE_F_NONBLOCK) { if (!ret) ret = -EAGAIN; break; } if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } if (do_wakeup) { smp_mb(); if (waitqueue_active(&pipe->wait)) wake_up_interruptible_sync(&pipe->wait); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); do_wakeup = 0; } pipe_wait(pipe); } if (do_wakeup) { smp_mb(); if (waitqueue_active(&pipe->wait)) wake_up_interruptible(&pipe->wait); kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } return ret; } ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags, splice_actor *actor) { ssize_t ret; struct inode *inode = out->f_mapping->host; /* * The actor worker might be calling ->prepare_write and * ->commit_write. Most of the time, these expect i_mutex to * be held. Since this may result in an ABBA deadlock with * pipe->inode, we have to order lock acquiry here. */ inode_double_lock(inode, pipe->inode); ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor); inode_double_unlock(inode, pipe->inode); return ret; } /** * generic_file_splice_write_nolock - generic_file_splice_write without mutexes * @pipe: pipe info * @out: file to write to * @len: number of bytes to splice * @flags: splice modifier flags * * Will either move or copy pages (determined by @flags options) from * the given pipe inode to the given file. The caller is responsible * for acquiring i_mutex on both inodes. * */ ssize_t generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { struct address_space *mapping = out->f_mapping; struct inode *inode = mapping->host; ssize_t ret; int err; ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file); if (ret > 0) { *ppos += ret; /* * If file or inode is SYNC and we actually wrote some data, * sync it. */ if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) { err = generic_osync_inode(inode, mapping, OSYNC_METADATA|OSYNC_DATA); if (err) ret = err; } } return ret; } EXPORT_SYMBOL(generic_file_splice_write_nolock); /** * generic_file_splice_write - splice data from a pipe to a file * @pipe: pipe info * @out: file to write to * @len: number of bytes to splice * @flags: splice modifier flags * * Will either move or copy pages (determined by @flags options) from * the given pipe inode to the given file. * */ ssize_t generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { struct address_space *mapping = out->f_mapping; ssize_t ret; ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file); if (ret > 0) { struct inode *inode = mapping->host; *ppos += ret; /* * If file or inode is SYNC and we actually wrote some data, * sync it. */ if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) { int err; mutex_lock(&inode->i_mutex); err = generic_osync_inode(inode, mapping, OSYNC_METADATA|OSYNC_DATA); mutex_unlock(&inode->i_mutex); if (err) ret = err; } } return ret; } EXPORT_SYMBOL(generic_file_splice_write); /** * generic_splice_sendpage - splice data from a pipe to a socket * @inode: pipe inode * @out: socket to write to * @len: number of bytes to splice * @flags: splice modifier flags * * Will send @len bytes from the pipe to a network socket. No data copying * is involved. * */ ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage); } EXPORT_SYMBOL(generic_splice_sendpage); /* * Attempt to initiate a splice from pipe to file. */ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out, loff_t *ppos, size_t len, unsigned int flags) { int ret; if (unlikely(!out->f_op || !out->f_op->splice_write)) return -EINVAL; if (unlikely(!(out->f_mode & FMODE_WRITE))) return -EBADF; ret = rw_verify_area(WRITE, out, ppos, len); if (unlikely(ret < 0)) return ret; return out->f_op->splice_write(pipe, out, ppos, len, flags); } /* * Attempt to initiate a splice from a file to a pipe. */ static long do_splice_to(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { loff_t isize, left; int ret; if (unlikely(!in->f_op || !in->f_op->splice_read)) return -EINVAL; if (unlikely(!(in->f_mode & FMODE_READ))) return -EBADF; ret = rw_verify_area(READ, in, ppos, len); if (unlikely(ret < 0)) return ret; isize = i_size_read(in->f_mapping->host); if (unlikely(*ppos >= isize)) return 0; left = isize - *ppos; if (unlikely(left < len)) len = left; return in->f_op->splice_read(in, ppos, pipe, len, flags); } long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, size_t len, unsigned int flags) { struct pipe_inode_info *pipe; long ret, bytes; loff_t out_off; umode_t i_mode; int i; /* * We require the input being a regular file, as we don't want to * randomly drop data for eg socket -> socket splicing. Use the * piped splicing for that! */ i_mode = in->f_dentry->d_inode->i_mode; if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) return -EINVAL; /* * neither in nor out is a pipe, setup an internal pipe attached to * 'out' and transfer the wanted data from 'in' to 'out' through that */ pipe = current->splice_pipe; if (unlikely(!pipe)) { pipe = alloc_pipe_info(NULL); if (!pipe) return -ENOMEM; /* * We don't have an immediate reader, but we'll read the stuff * out of the pipe right after the splice_to_pipe(). So set * PIPE_READERS appropriately. */ pipe->readers = 1; current->splice_pipe = pipe; } /* * Do the splice. */ ret = 0; bytes = 0; out_off = 0; while (len) { size_t read_len, max_read_len; /* * Do at most PIPE_BUFFERS pages worth of transfer: */ max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE)); ret = do_splice_to(in, ppos, pipe, max_read_len, flags); if (unlikely(ret < 0)) goto out_release; read_len = ret; /* * NOTE: nonblocking mode only applies to the input. We * must not do the output in nonblocking mode as then we * could get stuck data in the internal pipe: */ ret = do_splice_from(pipe, out, &out_off, read_len, flags & ~SPLICE_F_NONBLOCK); if (unlikely(ret < 0)) goto out_release; bytes += ret; len -= ret; /* * In nonblocking mode, if we got back a short read then * that was due to either an IO error or due to the * pagecache entry not being there. In the IO error case * the _next_ splice attempt will produce a clean IO error * return value (not a short read), so in both cases it's * correct to break out of the loop here: */ if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len)) break; } pipe->nrbufs = pipe->curbuf = 0; return bytes; out_release: /* * If we did an incomplete transfer we must release * the pipe buffers in question: */ for (i = 0; i < PIPE_BUFFERS; i++) { struct pipe_buffer *buf = pipe->bufs + i; if (buf->ops) { buf->ops->release(pipe, buf); buf->ops = NULL; } } pipe->nrbufs = pipe->curbuf = 0; /* * If we transferred some data, return the number of bytes: */ if (bytes > 0) return bytes; return ret; } EXPORT_SYMBOL(do_splice_direct); /* * Determine where to splice to/from. */ static long do_splice(struct file *in, loff_t __user *off_in, struct file *out, loff_t __user *off_out, size_t len, unsigned int flags) { struct pipe_inode_info *pipe; loff_t offset, *off; long ret; pipe = in->f_dentry->d_inode->i_pipe; if (pipe) { if (off_in) return -ESPIPE; if (off_out) { if (out->f_op->llseek == no_llseek) return -EINVAL; if (copy_from_user(&offset, off_out, sizeof(loff_t))) return -EFAULT; off = &offset; } else off = &out->f_pos; ret = do_splice_from(pipe, out, off, len, flags); if (off_out && copy_to_user(off_out, off, sizeof(loff_t))) ret = -EFAULT; return ret; } pipe = out->f_dentry->d_inode->i_pipe; if (pipe) { if (off_out) return -ESPIPE; if (off_in) { if (in->f_op->llseek == no_llseek) return -EINVAL; if (copy_from_user(&offset, off_in, sizeof(loff_t))) return -EFAULT; off = &offset; } else off = &in->f_pos; ret = do_splice_to(in, off, pipe, len, flags); if (off_in && copy_to_user(off_in, off, sizeof(loff_t))) ret = -EFAULT; return ret; } return -EINVAL; } /* * Map an iov into an array of pages and offset/length tupples. With the * partial_page structure, we can map several non-contiguous ranges into * our ones pages[] map instead of splitting that operation into pieces. * Could easily be exported as a generic helper for other users, in which * case one would probably want to add a 'max_nr_pages' parameter as well. */ static int get_iovec_page_array(const struct iovec __user *iov, unsigned int nr_vecs, struct page **pages, struct partial_page *partial, int aligned) { int buffers = 0, error = 0; /* * It's ok to take the mmap_sem for reading, even * across a "get_user()". */ down_read(¤t->mm->mmap_sem); while (nr_vecs) { unsigned long off, npages; void __user *base; size_t len; int i; /* * Get user address base and length for this iovec. */ error = get_user(base, &iov->iov_base); if (unlikely(error)) break; error = get_user(len, &iov->iov_len); if (unlikely(error)) break; /* * Sanity check this iovec. 0 read succeeds. */ if (unlikely(!len)) break; error = -EFAULT; if (unlikely(!base)) break; /* * Get this base offset and number of pages, then map * in the user pages. */ off = (unsigned long) base & ~PAGE_MASK; /* * If asked for alignment, the offset must be zero and the * length a multiple of the PAGE_SIZE. */ error = -EINVAL; if (aligned && (off || len & ~PAGE_MASK)) break; npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT; if (npages > PIPE_BUFFERS - buffers) npages = PIPE_BUFFERS - buffers; error = get_user_pages(current, current->mm, (unsigned long) base, npages, 0, 0, &pages[buffers], NULL); if (unlikely(error <= 0)) break; /* * Fill this contiguous range into the partial page map. */ for (i = 0; i < error; i++) { const int plen = min_t(size_t, len, PAGE_SIZE - off); partial[buffers].offset = off; partial[buffers].len = plen; off = 0; len -= plen; buffers++; } /* * We didn't complete this iov, stop here since it probably * means we have to move some of this into a pipe to * be able to continue. */ if (len) break; /* * Don't continue if we mapped fewer pages than we asked for, * or if we mapped the max number of pages that we have * room for. */ if (error < npages || buffers == PIPE_BUFFERS) break; nr_vecs--; iov++; } up_read(¤t->mm->mmap_sem); if (buffers) return buffers; return error; } /* * vmsplice splices a user address range into a pipe. It can be thought of * as splice-from-memory, where the regular splice is splice-from-file (or * to file). In both cases the output is a pipe, naturally. * * Note that vmsplice only supports splicing _from_ user memory to a pipe, * not the other way around. Splicing from user memory is a simple operation * that can be supported without any funky alignment restrictions or nasty * vm tricks. We simply map in the user memory and fill them into a pipe. * The reverse isn't quite as easy, though. There are two possible solutions * for that: * * - memcpy() the data internally, at which point we might as well just * do a regular read() on the buffer anyway. * - Lots of nasty vm tricks, that are neither fast nor flexible (it * has restriction limitations on both ends of the pipe). * * Alas, it isn't here. * */ static long do_vmsplice(struct file *file, const struct iovec __user *iov, unsigned long nr_segs, unsigned int flags) { struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe; struct page *pages[PIPE_BUFFERS]; struct partial_page partial[PIPE_BUFFERS]; struct splice_pipe_desc spd = { .pages = pages, .partial = partial, .flags = flags, .ops = &user_page_pipe_buf_ops, }; if (unlikely(!pipe)) return -EBADF; if (unlikely(nr_segs > UIO_MAXIOV)) return -EINVAL; else if (unlikely(!nr_segs)) return 0; spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial, flags & SPLICE_F_GIFT); if (spd.nr_pages <= 0) return spd.nr_pages; return splice_to_pipe(pipe, &spd); } asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov, unsigned long nr_segs, unsigned int flags) { struct file *file; long error; int fput; error = -EBADF; file = fget_light(fd, &fput); if (file) { if (file->f_mode & FMODE_WRITE) error = do_vmsplice(file, iov, nr_segs, flags); fput_light(file, fput); } return error; } asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, int fd_out, loff_t __user *off_out, size_t len, unsigned int flags) { long error; struct file *in, *out; int fput_in, fput_out; if (unlikely(!len)) return 0; error = -EBADF; in = fget_light(fd_in, &fput_in); if (in) { if (in->f_mode & FMODE_READ) { out = fget_light(fd_out, &fput_out); if (out) { if (out->f_mode & FMODE_WRITE) error = do_splice(in, off_in, out, off_out, len, flags); fput_light(out, fput_out); } } fput_light(in, fput_in); } return error; } /* * Make sure there's data to read. Wait for input if we can, otherwise * return an appropriate error. */ static int link_ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) { int ret; /* * Check ->nrbufs without the inode lock first. This function * is speculative anyways, so missing one is ok. */ if (pipe->nrbufs) return 0; ret = 0; mutex_lock(&pipe->inode->i_mutex); while (!pipe->nrbufs) { if (signal_pending(current)) { ret = -ERESTARTSYS; break; } if (!pipe->writers) break; if (!pipe->waiting_writers) { if (flags & SPLICE_F_NONBLOCK) { ret = -EAGAIN; break; } } pipe_wait(pipe); } mutex_unlock(&pipe->inode->i_mutex); return ret; } /* * Make sure there's writeable room. Wait for room if we can, otherwise * return an appropriate error. */ static int link_opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) { int ret; /* * Check ->nrbufs without the inode lock first. This function * is speculative anyways, so missing one is ok. */ if (pipe->nrbufs < PIPE_BUFFERS) return 0; ret = 0; mutex_lock(&pipe->inode->i_mutex); while (pipe->nrbufs >= PIPE_BUFFERS) { if (!pipe->readers) { send_sig(SIGPIPE, current, 0); ret = -EPIPE; break; } if (flags & SPLICE_F_NONBLOCK) { ret = -EAGAIN; break; } if (signal_pending(current)) { ret = -ERESTARTSYS; break; } pipe->waiting_writers++; pipe_wait(pipe); pipe->waiting_writers--; } mutex_unlock(&pipe->inode->i_mutex); return ret; } /* * Link contents of ipipe to opipe. */ static int link_pipe(struct pipe_inode_info *ipipe, struct pipe_inode_info *opipe, size_t len, unsigned int flags) { struct pipe_buffer *ibuf, *obuf; int ret = 0, i = 0, nbuf; /* * Potential ABBA deadlock, work around it by ordering lock * grabbing by inode address. Otherwise two different processes * could deadlock (one doing tee from A -> B, the other from B -> A). */ inode_double_lock(ipipe->inode, opipe->inode); do { if (!opipe->readers) { send_sig(SIGPIPE, current, 0); if (!ret) ret = -EPIPE; break; } /* * If we have iterated all input buffers or ran out of * output room, break. */ if (i >= ipipe->nrbufs || opipe->nrbufs >= PIPE_BUFFERS) break; ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1)); nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1); /* * Get a reference to this pipe buffer, * so we can copy the contents over. */ ibuf->ops->get(ipipe, ibuf); obuf = opipe->bufs + nbuf; *obuf = *ibuf; /* * Don't inherit the gift flag, we need to * prevent multiple steals of this page. */ obuf->flags &= ~PIPE_BUF_FLAG_GIFT; if (obuf->len > len) obuf->len = len; opipe->nrbufs++; ret += obuf->len; len -= obuf->len; i++; } while (len); inode_double_unlock(ipipe->inode, opipe->inode); /* * If we put data in the output pipe, wakeup any potential readers. */ if (ret > 0) { smp_mb(); if (waitqueue_active(&opipe->wait)) wake_up_interruptible(&opipe->wait); kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); } return ret; } /* * This is a tee(1) implementation that works on pipes. It doesn't copy * any data, it simply references the 'in' pages on the 'out' pipe. * The 'flags' used are the SPLICE_F_* variants, currently the only * applicable one is SPLICE_F_NONBLOCK. */ static long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags) { struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe; struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe; int ret = -EINVAL; /* * Duplicate the contents of ipipe to opipe without actually * copying the data. */ if (ipipe && opipe && ipipe != opipe) { /* * Keep going, unless we encounter an error. The ipipe/opipe * ordering doesn't really matter. */ ret = link_ipipe_prep(ipipe, flags); if (!ret) { ret = link_opipe_prep(opipe, flags); if (!ret) { ret = link_pipe(ipipe, opipe, len, flags); if (!ret && (flags & SPLICE_F_NONBLOCK)) ret = -EAGAIN; } } } return ret; } asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags) { struct file *in; int error, fput_in; if (unlikely(!len)) return 0; error = -EBADF; in = fget_light(fdin, &fput_in); if (in) { if (in->f_mode & FMODE_READ) { int fput_out; struct file *out = fget_light(fdout, &fput_out); if (out) { if (out->f_mode & FMODE_WRITE) error = do_tee(in, out, len, flags); fput_light(out, fput_out); } } fput_light(in, fput_in); } return error; }