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Diffstat (limited to 'fs/splice.c')
| -rw-r--r-- | fs/splice.c | 1745 |
1 files changed, 1745 insertions, 0 deletions
diff --git a/fs/splice.c b/fs/splice.c new file mode 100644 index 000000000..d0230cf8e --- /dev/null +++ b/fs/splice.c @@ -0,0 +1,1745 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * "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 <axboe@kernel.dk> + * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org> + * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu> + * + */ +#include <linux/bvec.h> +#include <linux/fs.h> +#include <linux/file.h> +#include <linux/pagemap.h> +#include <linux/splice.h> +#include <linux/memcontrol.h> +#include <linux/mm_inline.h> +#include <linux/swap.h> +#include <linux/writeback.h> +#include <linux/export.h> +#include <linux/syscalls.h> +#include <linux/uio.h> +#include <linux/security.h> +#include <linux/gfp.h> +#include <linux/socket.h> +#include <linux/sched/signal.h> + +#include "internal.h" + +/* + * 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 bool page_cache_pipe_buf_try_steal(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + struct folio *folio = page_folio(buf->page); + struct address_space *mapping; + + folio_lock(folio); + + mapping = folio_mapping(folio); + if (mapping) { + WARN_ON(!folio_test_uptodate(folio)); + + /* + * At least for ext2 with nobh option, we need to wait on + * writeback completing on this folio, since we'll remove it + * from the pagecache. Otherwise truncate wont wait on the + * folio, allowing the disk blocks to be reused by someone else + * before we actually wrote our data to them. fs corruption + * ensues. + */ + folio_wait_writeback(folio); + + if (!filemap_release_folio(folio, GFP_KERNEL)) + goto out_unlock; + + /* + * If we succeeded in removing the mapping, set LRU flag + * and return good. + */ + if (remove_mapping(mapping, folio)) { + buf->flags |= PIPE_BUF_FLAG_LRU; + return true; + } + } + + /* + * Raced with truncate or failed to remove folio from current + * address space, unlock and return failure. + */ +out_unlock: + folio_unlock(folio); + return false; +} + +static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + put_page(buf->page); + buf->flags &= ~PIPE_BUF_FLAG_LRU; +} + +/* + * Check whether the contents of buf is OK to access. Since the content + * is a page cache page, IO may be in flight. + */ +static int page_cache_pipe_buf_confirm(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; +} + +const struct pipe_buf_operations page_cache_pipe_buf_ops = { + .confirm = page_cache_pipe_buf_confirm, + .release = page_cache_pipe_buf_release, + .try_steal = page_cache_pipe_buf_try_steal, + .get = generic_pipe_buf_get, +}; + +static bool user_page_pipe_buf_try_steal(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + if (!(buf->flags & PIPE_BUF_FLAG_GIFT)) + return false; + + buf->flags |= PIPE_BUF_FLAG_LRU; + return generic_pipe_buf_try_steal(pipe, buf); +} + +static const struct pipe_buf_operations user_page_pipe_buf_ops = { + .release = page_cache_pipe_buf_release, + .try_steal = user_page_pipe_buf_try_steal, + .get = generic_pipe_buf_get, +}; + +static void wakeup_pipe_readers(struct pipe_inode_info *pipe) +{ + smp_mb(); + if (waitqueue_active(&pipe->rd_wait)) + wake_up_interruptible(&pipe->rd_wait); + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); +} + +/** + * splice_to_pipe - fill passed data into a pipe + * @pipe: pipe to fill + * @spd: data to fill + * + * Description: + * @spd contains a map of pages and len/offset tuples, along with + * the struct pipe_buf_operations associated with these pages. This + * function will link that data to the pipe. + * + */ +ssize_t splice_to_pipe(struct pipe_inode_info *pipe, + struct splice_pipe_desc *spd) +{ + unsigned int spd_pages = spd->nr_pages; + unsigned int tail = pipe->tail; + unsigned int head = pipe->head; + unsigned int mask = pipe->ring_size - 1; + int ret = 0, page_nr = 0; + + if (!spd_pages) + return 0; + + if (unlikely(!pipe->readers)) { + send_sig(SIGPIPE, current, 0); + ret = -EPIPE; + goto out; + } + + while (!pipe_full(head, tail, pipe->max_usage)) { + struct pipe_buffer *buf = &pipe->bufs[head & mask]; + + buf->page = spd->pages[page_nr]; + buf->offset = spd->partial[page_nr].offset; + buf->len = spd->partial[page_nr].len; + buf->private = spd->partial[page_nr].private; + buf->ops = spd->ops; + buf->flags = 0; + + head++; + pipe->head = head; + page_nr++; + ret += buf->len; + + if (!--spd->nr_pages) + break; + } + + if (!ret) + ret = -EAGAIN; + +out: + while (page_nr < spd_pages) + spd->spd_release(spd, page_nr++); + + return ret; +} +EXPORT_SYMBOL_GPL(splice_to_pipe); + +ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf) +{ + unsigned int head = pipe->head; + unsigned int tail = pipe->tail; + unsigned int mask = pipe->ring_size - 1; + int ret; + + if (unlikely(!pipe->readers)) { + send_sig(SIGPIPE, current, 0); + ret = -EPIPE; + } else if (pipe_full(head, tail, pipe->max_usage)) { + ret = -EAGAIN; + } else { + pipe->bufs[head & mask] = *buf; + pipe->head = head + 1; + return buf->len; + } + pipe_buf_release(pipe, buf); + return ret; +} +EXPORT_SYMBOL(add_to_pipe); + +/* + * Check if we need to grow the arrays holding pages and partial page + * descriptions. + */ +int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd) +{ + unsigned int max_usage = READ_ONCE(pipe->max_usage); + + spd->nr_pages_max = max_usage; + if (max_usage <= PIPE_DEF_BUFFERS) + return 0; + + spd->pages = kmalloc_array(max_usage, sizeof(struct page *), GFP_KERNEL); + spd->partial = kmalloc_array(max_usage, sizeof(struct partial_page), + GFP_KERNEL); + + if (spd->pages && spd->partial) + return 0; + + kfree(spd->pages); + kfree(spd->partial); + return -ENOMEM; +} + +void splice_shrink_spd(struct splice_pipe_desc *spd) +{ + if (spd->nr_pages_max <= PIPE_DEF_BUFFERS) + return; + + kfree(spd->pages); + kfree(spd->partial); +} + +/** + * generic_file_splice_read - splice data from file to a pipe + * @in: file to splice from + * @ppos: position in @in + * @pipe: pipe to splice to + * @len: number of bytes to splice + * @flags: splice modifier flags + * + * Description: + * Will read pages from given file and fill them into a pipe. Can be + * used as long as it has more or less sane ->read_iter(). + * + */ +ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, + struct pipe_inode_info *pipe, size_t len, + unsigned int flags) +{ + struct iov_iter to; + struct kiocb kiocb; + int ret; + + iov_iter_pipe(&to, ITER_DEST, pipe, len); + init_sync_kiocb(&kiocb, in); + kiocb.ki_pos = *ppos; + ret = call_read_iter(in, &kiocb, &to); + if (ret > 0) { + *ppos = kiocb.ki_pos; + file_accessed(in); + } else if (ret < 0) { + /* free what was emitted */ + pipe_discard_from(pipe, to.start_head); + /* + * callers of ->splice_read() expect -EAGAIN on + * "can't put anything in there", rather than -EFAULT. + */ + if (ret == -EFAULT) + ret = -EAGAIN; + } + + return ret; +} +EXPORT_SYMBOL(generic_file_splice_read); + +const struct pipe_buf_operations default_pipe_buf_ops = { + .release = generic_pipe_buf_release, + .try_steal = generic_pipe_buf_try_steal, + .get = generic_pipe_buf_get, +}; + +/* Pipe buffer operations for a socket and similar. */ +const struct pipe_buf_operations nosteal_pipe_buf_ops = { + .release = generic_pipe_buf_release, + .get = generic_pipe_buf_get, +}; +EXPORT_SYMBOL(nosteal_pipe_buf_ops); + +/* + * 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->u.file; + loff_t pos = sd->pos; + int more; + + if (!likely(file->f_op->sendpage)) + return -EINVAL; + + more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0; + + if (sd->len < sd->total_len && + pipe_occupancy(pipe->head, pipe->tail) > 1) + more |= MSG_SENDPAGE_NOTLAST; + + return file->f_op->sendpage(file, buf->page, buf->offset, + sd->len, &pos, more); +} + +static void wakeup_pipe_writers(struct pipe_inode_info *pipe) +{ + smp_mb(); + if (waitqueue_active(&pipe->wr_wait)) + wake_up_interruptible(&pipe->wr_wait); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); +} + +/** + * splice_from_pipe_feed - feed available data from a pipe to a file + * @pipe: pipe to splice from + * @sd: information to @actor + * @actor: handler that splices the data + * + * Description: + * This function loops over the pipe and calls @actor to do the + * actual moving of a single struct pipe_buffer to the desired + * destination. It returns when there's no more buffers left in + * the pipe or if the requested number of bytes (@sd->total_len) + * have been copied. It returns a positive number (one) if the + * pipe needs to be filled with more data, zero if the required + * number of bytes have been copied and -errno on error. + * + * This, together with splice_from_pipe_{begin,end,next}, may be + * used to implement the functionality of __splice_from_pipe() when + * locking is required around copying the pipe buffers to the + * destination. + */ +static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, + splice_actor *actor) +{ + unsigned int head = pipe->head; + unsigned int tail = pipe->tail; + unsigned int mask = pipe->ring_size - 1; + int ret; + + while (!pipe_empty(head, tail)) { + struct pipe_buffer *buf = &pipe->bufs[tail & mask]; + + sd->len = buf->len; + if (sd->len > sd->total_len) + sd->len = sd->total_len; + + ret = pipe_buf_confirm(pipe, buf); + if (unlikely(ret)) { + if (ret == -ENODATA) + ret = 0; + return ret; + } + + ret = actor(pipe, buf, sd); + if (ret <= 0) + return ret; + + buf->offset += ret; + buf->len -= ret; + + sd->num_spliced += ret; + sd->len -= ret; + sd->pos += ret; + sd->total_len -= ret; + + if (!buf->len) { + pipe_buf_release(pipe, buf); + tail++; + pipe->tail = tail; + if (pipe->files) + sd->need_wakeup = true; + } + + if (!sd->total_len) + return 0; + } + + return 1; +} + +/* We know we have a pipe buffer, but maybe it's empty? */ +static inline bool eat_empty_buffer(struct pipe_inode_info *pipe) +{ + unsigned int tail = pipe->tail; + unsigned int mask = pipe->ring_size - 1; + struct pipe_buffer *buf = &pipe->bufs[tail & mask]; + + if (unlikely(!buf->len)) { + pipe_buf_release(pipe, buf); + pipe->tail = tail+1; + return true; + } + + return false; +} + +/** + * splice_from_pipe_next - wait for some data to splice from + * @pipe: pipe to splice from + * @sd: information about the splice operation + * + * Description: + * This function will wait for some data and return a positive + * value (one) if pipe buffers are available. It will return zero + * or -errno if no more data needs to be spliced. + */ +static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) +{ + /* + * Check for signal early to make process killable when there are + * always buffers available + */ + if (signal_pending(current)) + return -ERESTARTSYS; + +repeat: + while (pipe_empty(pipe->head, pipe->tail)) { + if (!pipe->writers) + return 0; + + if (sd->num_spliced) + return 0; + + if (sd->flags & SPLICE_F_NONBLOCK) + return -EAGAIN; + + if (signal_pending(current)) + return -ERESTARTSYS; + + if (sd->need_wakeup) { + wakeup_pipe_writers(pipe); + sd->need_wakeup = false; + } + + pipe_wait_readable(pipe); + } + + if (eat_empty_buffer(pipe)) + goto repeat; + + return 1; +} + +/** + * splice_from_pipe_begin - start splicing from pipe + * @sd: information about the splice operation + * + * Description: + * This function should be called before a loop containing + * splice_from_pipe_next() and splice_from_pipe_feed() to + * initialize the necessary fields of @sd. + */ +static void splice_from_pipe_begin(struct splice_desc *sd) +{ + sd->num_spliced = 0; + sd->need_wakeup = false; +} + +/** + * splice_from_pipe_end - finish splicing from pipe + * @pipe: pipe to splice from + * @sd: information about the splice operation + * + * Description: + * This function will wake up pipe writers if necessary. It should + * be called after a loop containing splice_from_pipe_next() and + * splice_from_pipe_feed(). + */ +static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) +{ + if (sd->need_wakeup) + wakeup_pipe_writers(pipe); +} + +/** + * __splice_from_pipe - splice data from a pipe to given actor + * @pipe: pipe to splice from + * @sd: information to @actor + * @actor: handler that splices the data + * + * Description: + * This function does little more than loop over the pipe and call + * @actor to do the actual moving of a single struct pipe_buffer to + * the desired destination. See pipe_to_file, pipe_to_sendpage, or + * pipe_to_user. + * + */ +ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, + splice_actor *actor) +{ + int ret; + + splice_from_pipe_begin(sd); + do { + cond_resched(); + ret = splice_from_pipe_next(pipe, sd); + if (ret > 0) + ret = splice_from_pipe_feed(pipe, sd, actor); + } while (ret > 0); + splice_from_pipe_end(pipe, sd); + + return sd->num_spliced ? sd->num_spliced : ret; +} +EXPORT_SYMBOL(__splice_from_pipe); + +/** + * splice_from_pipe - splice data from a pipe to a file + * @pipe: pipe to splice from + * @out: file to splice to + * @ppos: position in @out + * @len: how many bytes to splice + * @flags: splice modifier flags + * @actor: handler that splices the data + * + * Description: + * See __splice_from_pipe. This function locks the pipe inode, + * otherwise it's identical to __splice_from_pipe(). + * + */ +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 splice_desc sd = { + .total_len = len, + .flags = flags, + .pos = *ppos, + .u.file = out, + }; + + pipe_lock(pipe); + ret = __splice_from_pipe(pipe, &sd, actor); + pipe_unlock(pipe); + + return ret; +} + +/** + * iter_file_splice_write - splice data from a pipe to a file + * @pipe: pipe info + * @out: file to write to + * @ppos: position in @out + * @len: number of bytes to splice + * @flags: splice modifier flags + * + * Description: + * Will either move or copy pages (determined by @flags options) from + * the given pipe inode to the given file. + * This one is ->write_iter-based. + * + */ +ssize_t +iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out, + loff_t *ppos, size_t len, unsigned int flags) +{ + struct splice_desc sd = { + .total_len = len, + .flags = flags, + .pos = *ppos, + .u.file = out, + }; + int nbufs = pipe->max_usage; + struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec), + GFP_KERNEL); + ssize_t ret; + + if (unlikely(!array)) + return -ENOMEM; + + pipe_lock(pipe); + + splice_from_pipe_begin(&sd); + while (sd.total_len) { + struct iov_iter from; + unsigned int head, tail, mask; + size_t left; + int n; + + ret = splice_from_pipe_next(pipe, &sd); + if (ret <= 0) + break; + + if (unlikely(nbufs < pipe->max_usage)) { + kfree(array); + nbufs = pipe->max_usage; + array = kcalloc(nbufs, sizeof(struct bio_vec), + GFP_KERNEL); + if (!array) { + ret = -ENOMEM; + break; + } + } + + head = pipe->head; + tail = pipe->tail; + mask = pipe->ring_size - 1; + + /* build the vector */ + left = sd.total_len; + for (n = 0; !pipe_empty(head, tail) && left && n < nbufs; tail++) { + struct pipe_buffer *buf = &pipe->bufs[tail & mask]; + size_t this_len = buf->len; + + /* zero-length bvecs are not supported, skip them */ + if (!this_len) + continue; + this_len = min(this_len, left); + + ret = pipe_buf_confirm(pipe, buf); + if (unlikely(ret)) { + if (ret == -ENODATA) + ret = 0; + goto done; + } + + array[n].bv_page = buf->page; + array[n].bv_len = this_len; + array[n].bv_offset = buf->offset; + left -= this_len; + n++; + } + + iov_iter_bvec(&from, ITER_SOURCE, array, n, sd.total_len - left); + ret = vfs_iter_write(out, &from, &sd.pos, 0); + if (ret <= 0) + break; + + sd.num_spliced += ret; + sd.total_len -= ret; + *ppos = sd.pos; + + /* dismiss the fully eaten buffers, adjust the partial one */ + tail = pipe->tail; + while (ret) { + struct pipe_buffer *buf = &pipe->bufs[tail & mask]; + if (ret >= buf->len) { + ret -= buf->len; + buf->len = 0; + pipe_buf_release(pipe, buf); + tail++; + pipe->tail = tail; + if (pipe->files) + sd.need_wakeup = true; + } else { + buf->offset += ret; + buf->len -= ret; + ret = 0; + } + } + } +done: + kfree(array); + splice_from_pipe_end(pipe, &sd); + + pipe_unlock(pipe); + + if (sd.num_spliced) + ret = sd.num_spliced; + + return ret; +} + +EXPORT_SYMBOL(iter_file_splice_write); + +/** + * generic_splice_sendpage - splice data from a pipe to a socket + * @pipe: pipe to splice from + * @out: socket to write to + * @ppos: position in @out + * @len: number of bytes to splice + * @flags: splice modifier flags + * + * Description: + * 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); + +static int warn_unsupported(struct file *file, const char *op) +{ + pr_debug_ratelimited( + "splice %s not supported for file %pD4 (pid: %d comm: %.20s)\n", + op, file, current->pid, current->comm); + return -EINVAL; +} + +/* + * 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) +{ + if (unlikely(!out->f_op->splice_write)) + return warn_unsupported(out, "write"); + return out->f_op->splice_write(pipe, out, ppos, len, flags); +} + +/* + * Indicate to the caller that there was a premature EOF when reading from the + * source and the caller didn't indicate they would be sending more data after + * this. + */ +static void do_splice_eof(struct splice_desc *sd) +{ + if (sd->splice_eof) + sd->splice_eof(sd); +} + +/* + * 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) +{ + unsigned int p_space; + int ret; + + if (unlikely(!(in->f_mode & FMODE_READ))) + return -EBADF; + + /* Don't try to read more the pipe has space for. */ + p_space = pipe->max_usage - pipe_occupancy(pipe->head, pipe->tail); + len = min_t(size_t, len, p_space << PAGE_SHIFT); + + ret = rw_verify_area(READ, in, ppos, len); + if (unlikely(ret < 0)) + return ret; + + if (unlikely(len > MAX_RW_COUNT)) + len = MAX_RW_COUNT; + + if (unlikely(!in->f_op->splice_read)) + return warn_unsupported(in, "read"); + return in->f_op->splice_read(in, ppos, pipe, len, flags); +} + +/** + * splice_direct_to_actor - splices data directly between two non-pipes + * @in: file to splice from + * @sd: actor information on where to splice to + * @actor: handles the data splicing + * + * Description: + * This is a special case helper to splice directly between two + * points, without requiring an explicit pipe. Internally an allocated + * pipe is cached in the process, and reused during the lifetime of + * that process. + * + */ +ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, + splice_direct_actor *actor) +{ + struct pipe_inode_info *pipe; + long ret, bytes; + size_t len; + int i, flags, more; + + /* + * We require the input to be seekable, as we don't want to randomly + * drop data for eg socket -> socket splicing. Use the piped splicing + * for that! + */ + if (unlikely(!(in->f_mode & FMODE_LSEEK))) + 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(); + 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; + len = sd->total_len; + flags = sd->flags; + + /* + * Don't block on output, we have to drain the direct pipe. + */ + sd->flags &= ~SPLICE_F_NONBLOCK; + more = sd->flags & SPLICE_F_MORE; + + WARN_ON_ONCE(!pipe_empty(pipe->head, pipe->tail)); + + while (len) { + size_t read_len; + loff_t pos = sd->pos, prev_pos = pos; + + ret = do_splice_to(in, &pos, pipe, len, flags); + if (unlikely(ret <= 0)) + goto read_failure; + + read_len = ret; + sd->total_len = read_len; + + /* + * If more data is pending, set SPLICE_F_MORE + * If this is the last data and SPLICE_F_MORE was not set + * initially, clears it. + */ + if (read_len < len) + sd->flags |= SPLICE_F_MORE; + else if (!more) + sd->flags &= ~SPLICE_F_MORE; + /* + * 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 = actor(pipe, sd); + if (unlikely(ret <= 0)) { + sd->pos = prev_pos; + goto out_release; + } + + bytes += ret; + len -= ret; + sd->pos = pos; + + if (ret < read_len) { + sd->pos = prev_pos + ret; + goto out_release; + } + } + +done: + pipe->tail = pipe->head = 0; + file_accessed(in); + return bytes; + +read_failure: + /* + * If the user did *not* set SPLICE_F_MORE *and* we didn't hit that + * "use all of len" case that cleared SPLICE_F_MORE, *and* we did a + * "->splice_in()" that returned EOF (ie zero) *and* we have sent at + * least 1 byte *then* we will also do the ->splice_eof() call. + */ + if (ret == 0 && !more && len > 0 && bytes) + do_splice_eof(sd); +out_release: + /* + * If we did an incomplete transfer we must release + * the pipe buffers in question: + */ + for (i = 0; i < pipe->ring_size; i++) { + struct pipe_buffer *buf = &pipe->bufs[i]; + + if (buf->ops) + pipe_buf_release(pipe, buf); + } + + if (!bytes) + bytes = ret; + + goto done; +} +EXPORT_SYMBOL(splice_direct_to_actor); + +static int direct_splice_actor(struct pipe_inode_info *pipe, + struct splice_desc *sd) +{ + struct file *file = sd->u.file; + + return do_splice_from(pipe, file, sd->opos, sd->total_len, + sd->flags); +} + +static void direct_file_splice_eof(struct splice_desc *sd) +{ + struct file *file = sd->u.file; + + if (file->f_op->splice_eof) + file->f_op->splice_eof(file); +} + +/** + * do_splice_direct - splices data directly between two files + * @in: file to splice from + * @ppos: input file offset + * @out: file to splice to + * @opos: output file offset + * @len: number of bytes to splice + * @flags: splice modifier flags + * + * Description: + * For use by do_sendfile(). splice can easily emulate sendfile, but + * doing it in the application would incur an extra system call + * (splice in + splice out, as compared to just sendfile()). So this helper + * can splice directly through a process-private pipe. + * + */ +long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, + loff_t *opos, size_t len, unsigned int flags) +{ + struct splice_desc sd = { + .len = len, + .total_len = len, + .flags = flags, + .pos = *ppos, + .u.file = out, + .splice_eof = direct_file_splice_eof, + .opos = opos, + }; + long ret; + + if (unlikely(!(out->f_mode & FMODE_WRITE))) + return -EBADF; + + if (unlikely(out->f_flags & O_APPEND)) + return -EINVAL; + + ret = rw_verify_area(WRITE, out, opos, len); + if (unlikely(ret < 0)) + return ret; + + ret = splice_direct_to_actor(in, &sd, direct_splice_actor); + if (ret > 0) + *ppos = sd.pos; + + return ret; +} +EXPORT_SYMBOL(do_splice_direct); + +static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags) +{ + for (;;) { + if (unlikely(!pipe->readers)) { + send_sig(SIGPIPE, current, 0); + return -EPIPE; + } + if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) + return 0; + if (flags & SPLICE_F_NONBLOCK) + return -EAGAIN; + if (signal_pending(current)) + return -ERESTARTSYS; + pipe_wait_writable(pipe); + } +} + +static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, + struct pipe_inode_info *opipe, + size_t len, unsigned int flags); + +long splice_file_to_pipe(struct file *in, + struct pipe_inode_info *opipe, + loff_t *offset, + size_t len, unsigned int flags) +{ + long ret; + + pipe_lock(opipe); + ret = wait_for_space(opipe, flags); + if (!ret) + ret = do_splice_to(in, offset, opipe, len, flags); + pipe_unlock(opipe); + if (ret > 0) + wakeup_pipe_readers(opipe); + return ret; +} + +/* + * Determine where to splice to/from. + */ +long do_splice(struct file *in, loff_t *off_in, struct file *out, + loff_t *off_out, size_t len, unsigned int flags) +{ + struct pipe_inode_info *ipipe; + struct pipe_inode_info *opipe; + loff_t offset; + long ret; + + if (unlikely(!(in->f_mode & FMODE_READ) || + !(out->f_mode & FMODE_WRITE))) + return -EBADF; + + ipipe = get_pipe_info(in, true); + opipe = get_pipe_info(out, true); + + if (ipipe && opipe) { + if (off_in || off_out) + return -ESPIPE; + + /* Splicing to self would be fun, but... */ + if (ipipe == opipe) + return -EINVAL; + + if ((in->f_flags | out->f_flags) & O_NONBLOCK) + flags |= SPLICE_F_NONBLOCK; + + return splice_pipe_to_pipe(ipipe, opipe, len, flags); + } + + if (ipipe) { + if (off_in) + return -ESPIPE; + if (off_out) { + if (!(out->f_mode & FMODE_PWRITE)) + return -EINVAL; + offset = *off_out; + } else { + offset = out->f_pos; + } + + if (unlikely(out->f_flags & O_APPEND)) + return -EINVAL; + + ret = rw_verify_area(WRITE, out, &offset, len); + if (unlikely(ret < 0)) + return ret; + + if (in->f_flags & O_NONBLOCK) + flags |= SPLICE_F_NONBLOCK; + + file_start_write(out); + ret = do_splice_from(ipipe, out, &offset, len, flags); + file_end_write(out); + + if (!off_out) + out->f_pos = offset; + else + *off_out = offset; + + return ret; + } + + if (opipe) { + if (off_out) + return -ESPIPE; + if (off_in) { + if (!(in->f_mode & FMODE_PREAD)) + return -EINVAL; + offset = *off_in; + } else { + offset = in->f_pos; + } + + if (out->f_flags & O_NONBLOCK) + flags |= SPLICE_F_NONBLOCK; + + ret = splice_file_to_pipe(in, opipe, &offset, len, flags); + if (!off_in) + in->f_pos = offset; + else + *off_in = offset; + + return ret; + } + + return -EINVAL; +} + +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 *ipipe; + struct pipe_inode_info *opipe; + loff_t offset, *__off_in = NULL, *__off_out = NULL; + long ret; + + ipipe = get_pipe_info(in, true); + opipe = get_pipe_info(out, true); + + if (ipipe && off_in) + return -ESPIPE; + if (opipe && off_out) + return -ESPIPE; + + if (off_out) { + if (copy_from_user(&offset, off_out, sizeof(loff_t))) + return -EFAULT; + __off_out = &offset; + } + if (off_in) { + if (copy_from_user(&offset, off_in, sizeof(loff_t))) + return -EFAULT; + __off_in = &offset; + } + + ret = do_splice(in, __off_in, out, __off_out, len, flags); + if (ret < 0) + return ret; + + if (__off_out && copy_to_user(off_out, __off_out, sizeof(loff_t))) + return -EFAULT; + if (__off_in && copy_to_user(off_in, __off_in, sizeof(loff_t))) + return -EFAULT; + + return ret; +} + +static int iter_to_pipe(struct iov_iter *from, + struct pipe_inode_info *pipe, + unsigned flags) +{ + struct pipe_buffer buf = { + .ops = &user_page_pipe_buf_ops, + .flags = flags + }; + size_t total = 0; + int ret = 0; + + while (iov_iter_count(from)) { + struct page *pages[16]; + ssize_t left; + size_t start; + int i, n; + + left = iov_iter_get_pages2(from, pages, ~0UL, 16, &start); + if (left <= 0) { + ret = left; + break; + } + + n = DIV_ROUND_UP(left + start, PAGE_SIZE); + for (i = 0; i < n; i++) { + int size = min_t(int, left, PAGE_SIZE - start); + + buf.page = pages[i]; + buf.offset = start; + buf.len = size; + ret = add_to_pipe(pipe, &buf); + if (unlikely(ret < 0)) { + iov_iter_revert(from, left); + // this one got dropped by add_to_pipe() + while (++i < n) + put_page(pages[i]); + goto out; + } + total += ret; + left -= size; + start = 0; + } + } +out: + return total ? total : ret; +} + +static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf, + struct splice_desc *sd) +{ + int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data); + return n == sd->len ? n : -EFAULT; +} + +/* + * For lack of a better implementation, implement vmsplice() to userspace + * as a simple copy of the pipes pages to the user iov. + */ +static long vmsplice_to_user(struct file *file, struct iov_iter *iter, + unsigned int flags) +{ + struct pipe_inode_info *pipe = get_pipe_info(file, true); + struct splice_desc sd = { + .total_len = iov_iter_count(iter), + .flags = flags, + .u.data = iter + }; + long ret = 0; + + if (!pipe) + return -EBADF; + + if (sd.total_len) { + pipe_lock(pipe); + ret = __splice_from_pipe(pipe, &sd, pipe_to_user); + pipe_unlock(pipe); + } + + return ret; +} + +/* + * 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. + */ +static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter, + unsigned int flags) +{ + struct pipe_inode_info *pipe; + long ret = 0; + unsigned buf_flag = 0; + + if (flags & SPLICE_F_GIFT) + buf_flag = PIPE_BUF_FLAG_GIFT; + + pipe = get_pipe_info(file, true); + if (!pipe) + return -EBADF; + + pipe_lock(pipe); + ret = wait_for_space(pipe, flags); + if (!ret) + ret = iter_to_pipe(iter, pipe, buf_flag); + pipe_unlock(pipe); + if (ret > 0) + wakeup_pipe_readers(pipe); + return ret; +} + +static int vmsplice_type(struct fd f, int *type) +{ + if (!f.file) + return -EBADF; + if (f.file->f_mode & FMODE_WRITE) { + *type = ITER_SOURCE; + } else if (f.file->f_mode & FMODE_READ) { + *type = ITER_DEST; + } else { + fdput(f); + return -EBADF; + } + return 0; +} + +/* + * Note that vmsplice only really supports true 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). + * + * Currently we punt and implement it as a normal copy, see pipe_to_user(). + * + */ +SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov, + unsigned long, nr_segs, unsigned int, flags) +{ + struct iovec iovstack[UIO_FASTIOV]; + struct iovec *iov = iovstack; + struct iov_iter iter; + ssize_t error; + struct fd f; + int type; + + if (unlikely(flags & ~SPLICE_F_ALL)) + return -EINVAL; + + f = fdget(fd); + error = vmsplice_type(f, &type); + if (error) + return error; + + error = import_iovec(type, uiov, nr_segs, + ARRAY_SIZE(iovstack), &iov, &iter); + if (error < 0) + goto out_fdput; + + if (!iov_iter_count(&iter)) + error = 0; + else if (type == ITER_SOURCE) + error = vmsplice_to_pipe(f.file, &iter, flags); + else + error = vmsplice_to_user(f.file, &iter, flags); + + kfree(iov); +out_fdput: + fdput(f); + return error; +} + +SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in, + int, fd_out, loff_t __user *, off_out, + size_t, len, unsigned int, flags) +{ + struct fd in, out; + long error; + + if (unlikely(!len)) + return 0; + + if (unlikely(flags & ~SPLICE_F_ALL)) + return -EINVAL; + + error = -EBADF; + in = fdget(fd_in); + if (in.file) { + out = fdget(fd_out); + if (out.file) { + error = __do_splice(in.file, off_in, out.file, off_out, + len, flags); + fdput(out); + } + fdput(in); + } + return error; +} + +/* + * Make sure there's data to read. Wait for input if we can, otherwise + * return an appropriate error. + */ +static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags) +{ + int ret; + + /* + * Check the pipe occupancy without the inode lock first. This function + * is speculative anyways, so missing one is ok. + */ + if (!pipe_empty(pipe->head, pipe->tail)) + return 0; + + ret = 0; + pipe_lock(pipe); + + while (pipe_empty(pipe->head, pipe->tail)) { + if (signal_pending(current)) { + ret = -ERESTARTSYS; + break; + } + if (!pipe->writers) + break; + if (flags & SPLICE_F_NONBLOCK) { + ret = -EAGAIN; + break; + } + pipe_wait_readable(pipe); + } + + pipe_unlock(pipe); + return ret; +} + +/* + * Make sure there's writeable room. Wait for room if we can, otherwise + * return an appropriate error. + */ +static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) +{ + int ret; + + /* + * Check pipe occupancy without the inode lock first. This function + * is speculative anyways, so missing one is ok. + */ + if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) + return 0; + + ret = 0; + pipe_lock(pipe); + + while (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) { + 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_wait_writable(pipe); + } + + pipe_unlock(pipe); + return ret; +} + +/* + * Splice contents of ipipe to opipe. + */ +static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe, + struct pipe_inode_info *opipe, + size_t len, unsigned int flags) +{ + struct pipe_buffer *ibuf, *obuf; + unsigned int i_head, o_head; + unsigned int i_tail, o_tail; + unsigned int i_mask, o_mask; + int ret = 0; + bool input_wakeup = false; + + +retry: + ret = ipipe_prep(ipipe, flags); + if (ret) + return ret; + + ret = opipe_prep(opipe, flags); + if (ret) + return ret; + + /* + * Potential ABBA deadlock, work around it by ordering lock + * grabbing by pipe info address. Otherwise two different processes + * could deadlock (one doing tee from A -> B, the other from B -> A). + */ + pipe_double_lock(ipipe, opipe); + + i_tail = ipipe->tail; + i_mask = ipipe->ring_size - 1; + o_head = opipe->head; + o_mask = opipe->ring_size - 1; + + do { + size_t o_len; + + if (!opipe->readers) { + send_sig(SIGPIPE, current, 0); + if (!ret) + ret = -EPIPE; + break; + } + + i_head = ipipe->head; + o_tail = opipe->tail; + + if (pipe_empty(i_head, i_tail) && !ipipe->writers) + break; + + /* + * Cannot make any progress, because either the input + * pipe is empty or the output pipe is full. + */ + if (pipe_empty(i_head, i_tail) || + pipe_full(o_head, o_tail, opipe->max_usage)) { + /* Already processed some buffers, break */ + if (ret) + break; + + if (flags & SPLICE_F_NONBLOCK) { + ret = -EAGAIN; + break; + } + + /* + * We raced with another reader/writer and haven't + * managed to process any buffers. A zero return + * value means EOF, so retry instead. + */ + pipe_unlock(ipipe); + pipe_unlock(opipe); + goto retry; + } + + ibuf = &ipipe->bufs[i_tail & i_mask]; + obuf = &opipe->bufs[o_head & o_mask]; + + if (len >= ibuf->len) { + /* + * Simply move the whole buffer from ipipe to opipe + */ + *obuf = *ibuf; + ibuf->ops = NULL; + i_tail++; + ipipe->tail = i_tail; + input_wakeup = true; + o_len = obuf->len; + o_head++; + opipe->head = o_head; + } else { + /* + * Get a reference to this pipe buffer, + * so we can copy the contents over. + */ + if (!pipe_buf_get(ipipe, ibuf)) { + if (ret == 0) + ret = -EFAULT; + break; + } + *obuf = *ibuf; + + /* + * Don't inherit the gift and merge flags, we need to + * prevent multiple steals of this page. + */ + obuf->flags &= ~PIPE_BUF_FLAG_GIFT; + obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE; + + obuf->len = len; + ibuf->offset += len; + ibuf->len -= len; + o_len = len; + o_head++; + opipe->head = o_head; + } + ret += o_len; + len -= o_len; + } while (len); + + pipe_unlock(ipipe); + pipe_unlock(opipe); + + /* + * If we put data in the output pipe, wakeup any potential readers. + */ + if (ret > 0) + wakeup_pipe_readers(opipe); + + if (input_wakeup) + wakeup_pipe_writers(ipipe); + + 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; + unsigned int i_head, o_head; + unsigned int i_tail, o_tail; + unsigned int i_mask, o_mask; + int ret = 0; + + /* + * Potential ABBA deadlock, work around it by ordering lock + * grabbing by pipe info address. Otherwise two different processes + * could deadlock (one doing tee from A -> B, the other from B -> A). + */ + pipe_double_lock(ipipe, opipe); + + i_tail = ipipe->tail; + i_mask = ipipe->ring_size - 1; + o_head = opipe->head; + o_mask = opipe->ring_size - 1; + + do { + if (!opipe->readers) { + send_sig(SIGPIPE, current, 0); + if (!ret) + ret = -EPIPE; + break; + } + + i_head = ipipe->head; + o_tail = opipe->tail; + + /* + * If we have iterated all input buffers or run out of + * output room, break. + */ + if (pipe_empty(i_head, i_tail) || + pipe_full(o_head, o_tail, opipe->max_usage)) + break; + + ibuf = &ipipe->bufs[i_tail & i_mask]; + obuf = &opipe->bufs[o_head & o_mask]; + + /* + * Get a reference to this pipe buffer, + * so we can copy the contents over. + */ + if (!pipe_buf_get(ipipe, ibuf)) { + if (ret == 0) + ret = -EFAULT; + break; + } + + *obuf = *ibuf; + + /* + * Don't inherit the gift and merge flag, we need to prevent + * multiple steals of this page. + */ + obuf->flags &= ~PIPE_BUF_FLAG_GIFT; + obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE; + + if (obuf->len > len) + obuf->len = len; + ret += obuf->len; + len -= obuf->len; + + o_head++; + opipe->head = o_head; + i_tail++; + } while (len); + + pipe_unlock(ipipe); + pipe_unlock(opipe); + + /* + * If we put data in the output pipe, wakeup any potential readers. + */ + if (ret > 0) + wakeup_pipe_readers(opipe); + + 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. + */ +long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags) +{ + struct pipe_inode_info *ipipe = get_pipe_info(in, true); + struct pipe_inode_info *opipe = get_pipe_info(out, true); + int ret = -EINVAL; + + if (unlikely(!(in->f_mode & FMODE_READ) || + !(out->f_mode & FMODE_WRITE))) + return -EBADF; + + /* + * Duplicate the contents of ipipe to opipe without actually + * copying the data. + */ + if (ipipe && opipe && ipipe != opipe) { + if ((in->f_flags | out->f_flags) & O_NONBLOCK) + flags |= SPLICE_F_NONBLOCK; + + /* + * Keep going, unless we encounter an error. The ipipe/opipe + * ordering doesn't really matter. + */ + ret = ipipe_prep(ipipe, flags); + if (!ret) { + ret = opipe_prep(opipe, flags); + if (!ret) + ret = link_pipe(ipipe, opipe, len, flags); + } + } + + return ret; +} + +SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags) +{ + struct fd in, out; + int error; + + if (unlikely(flags & ~SPLICE_F_ALL)) + return -EINVAL; + + if (unlikely(!len)) + return 0; + + error = -EBADF; + in = fdget(fdin); + if (in.file) { + out = fdget(fdout); + if (out.file) { + error = do_tee(in.file, out.file, len, flags); + fdput(out); + } + fdput(in); + } + + return error; +} |