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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /fs/splice.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c1745
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;
+}