v4.19.13 snapshot.
diff --git a/fs/splice.c b/fs/splice.c
new file mode 100644
index 0000000..b3daa97
--- /dev/null
+++ b/fs/splice.c
@@ -0,0 +1,1758 @@
+/*
+ * "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/compat.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 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 (page_has_private(page) &&
+ !try_to_release_page(page, GFP_KERNEL))
+ goto out_unlock;
+
+ /*
+ * 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.
+ */
+out_unlock:
+ unlock_page(page);
+ return 1;
+}
+
+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 = {
+ .can_merge = 0,
+ .confirm = page_cache_pipe_buf_confirm,
+ .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 const struct pipe_buf_operations user_page_pipe_buf_ops = {
+ .can_merge = 0,
+ .confirm = generic_pipe_buf_confirm,
+ .release = page_cache_pipe_buf_release,
+ .steal = user_page_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
+static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
+{
+ smp_mb();
+ if (waitqueue_active(&pipe->wait))
+ wake_up_interruptible(&pipe->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;
+ 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->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->private = spd->partial[page_nr].private;
+ buf->ops = spd->ops;
+ buf->flags = 0;
+
+ pipe->nrbufs++;
+ 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)
+{
+ int ret;
+
+ if (unlikely(!pipe->readers)) {
+ send_sig(SIGPIPE, current, 0);
+ ret = -EPIPE;
+ } else if (pipe->nrbufs == pipe->buffers) {
+ ret = -EAGAIN;
+ } else {
+ int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
+ pipe->bufs[newbuf] = *buf;
+ pipe->nrbufs++;
+ 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 buffers = READ_ONCE(pipe->buffers);
+
+ spd->nr_pages_max = buffers;
+ if (buffers <= PIPE_DEF_BUFFERS)
+ return 0;
+
+ spd->pages = kmalloc_array(buffers, sizeof(struct page *), GFP_KERNEL);
+ spd->partial = kmalloc_array(buffers, 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 idx, ret;
+
+ iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len);
+ idx = to.idx;
+ 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) {
+ to.idx = idx;
+ to.iov_offset = 0;
+ iov_iter_advance(&to, 0); /* to free what was emitted */
+ /*
+ * 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 = {
+ .can_merge = 0,
+ .confirm = generic_pipe_buf_confirm,
+ .release = generic_pipe_buf_release,
+ .steal = generic_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
+static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return 1;
+}
+
+/* Pipe buffer operations for a socket and similar. */
+const struct pipe_buf_operations nosteal_pipe_buf_ops = {
+ .can_merge = 0,
+ .confirm = generic_pipe_buf_confirm,
+ .release = generic_pipe_buf_release,
+ .steal = generic_pipe_buf_nosteal,
+ .get = generic_pipe_buf_get,
+};
+EXPORT_SYMBOL(nosteal_pipe_buf_ops);
+
+static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
+ unsigned long vlen, loff_t offset)
+{
+ mm_segment_t old_fs;
+ loff_t pos = offset;
+ ssize_t res;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ /* The cast to a user pointer is valid due to the set_fs() */
+ res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
+ set_fs(old_fs);
+
+ return res;
+}
+
+static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
+ struct iov_iter to;
+ struct page **pages;
+ unsigned int nr_pages;
+ size_t offset, base, copied = 0;
+ ssize_t res;
+ int i;
+
+ if (pipe->nrbufs == pipe->buffers)
+ return -EAGAIN;
+
+ /*
+ * Try to keep page boundaries matching to source pagecache ones -
+ * it probably won't be much help, but...
+ */
+ offset = *ppos & ~PAGE_MASK;
+
+ iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);
+
+ res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &base);
+ if (res <= 0)
+ return -ENOMEM;
+
+ nr_pages = DIV_ROUND_UP(res + base, PAGE_SIZE);
+
+ vec = __vec;
+ if (nr_pages > PIPE_DEF_BUFFERS) {
+ vec = kmalloc_array(nr_pages, sizeof(struct kvec), GFP_KERNEL);
+ if (unlikely(!vec)) {
+ res = -ENOMEM;
+ goto out;
+ }
+ }
+
+ pipe->bufs[to.idx].offset = offset;
+ pipe->bufs[to.idx].len -= offset;
+
+ for (i = 0; i < nr_pages; i++) {
+ size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
+ vec[i].iov_base = page_address(pages[i]) + offset;
+ vec[i].iov_len = this_len;
+ len -= this_len;
+ offset = 0;
+ }
+
+ res = kernel_readv(in, vec, nr_pages, *ppos);
+ if (res > 0) {
+ copied = res;
+ *ppos += res;
+ }
+
+ if (vec != __vec)
+ kfree(vec);
+out:
+ for (i = 0; i < nr_pages; i++)
+ put_page(pages[i]);
+ kvfree(pages);
+ iov_iter_advance(&to, copied); /* truncates and discards */
+ return res;
+}
+
+/*
+ * 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->nrbufs > 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->wait))
+ wake_up_interruptible(&pipe->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)
+{
+ int ret;
+
+ while (pipe->nrbufs) {
+ struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
+
+ 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);
+ pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
+ pipe->nrbufs--;
+ if (pipe->files)
+ sd->need_wakeup = true;
+ }
+
+ if (!sd->total_len)
+ return 0;
+ }
+
+ return 1;
+}
+
+/**
+ * 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;
+
+ while (!pipe->nrbufs) {
+ if (!pipe->writers)
+ return 0;
+
+ if (!pipe->waiting_writers && 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(pipe);
+ }
+
+ 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->buffers;
+ 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;
+ size_t left;
+ int n, idx;
+
+ ret = splice_from_pipe_next(pipe, &sd);
+ if (ret <= 0)
+ break;
+
+ if (unlikely(nbufs < pipe->buffers)) {
+ kfree(array);
+ nbufs = pipe->buffers;
+ array = kcalloc(nbufs, sizeof(struct bio_vec),
+ GFP_KERNEL);
+ if (!array) {
+ ret = -ENOMEM;
+ break;
+ }
+ }
+
+ /* build the vector */
+ left = sd.total_len;
+ for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
+ struct pipe_buffer *buf = pipe->bufs + idx;
+ size_t this_len = buf->len;
+
+ if (this_len > left)
+ this_len = left;
+
+ if (idx == pipe->buffers - 1)
+ idx = -1;
+
+ 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;
+ }
+
+ iov_iter_bvec(&from, ITER_BVEC | WRITE, 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 */
+ while (ret) {
+ struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
+ if (ret >= buf->len) {
+ ret -= buf->len;
+ buf->len = 0;
+ pipe_buf_release(pipe, buf);
+ pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
+ pipe->nrbufs--;
+ 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);
+
+static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
+ struct splice_desc *sd)
+{
+ int ret;
+ void *data;
+ loff_t tmp = sd->pos;
+
+ data = kmap(buf->page);
+ ret = __kernel_write(sd->u.file, data + buf->offset, sd->len, &tmp);
+ kunmap(buf->page);
+
+ return ret;
+}
+
+static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
+ struct file *out, loff_t *ppos,
+ size_t len, unsigned int flags)
+{
+ ssize_t ret;
+
+ ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
+ if (ret > 0)
+ *ppos += ret;
+
+ return ret;
+}
+
+/**
+ * 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);
+
+/*
+ * 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)
+{
+ ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
+ loff_t *, size_t, unsigned int);
+
+ if (out->f_op->splice_write)
+ splice_write = out->f_op->splice_write;
+ else
+ splice_write = default_file_splice_write;
+
+ return 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)
+{
+ ssize_t (*splice_read)(struct file *, loff_t *,
+ struct pipe_inode_info *, size_t, unsigned int);
+ int ret;
+
+ if (unlikely(!(in->f_mode & FMODE_READ)))
+ return -EBADF;
+
+ 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 (in->f_op->splice_read)
+ splice_read = in->f_op->splice_read;
+ else
+ splice_read = default_file_splice_read;
+
+ return 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;
+ umode_t i_mode;
+ size_t len;
+ int i, flags, more;
+
+ /*
+ * 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 = file_inode(in)->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();
+ 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;
+
+ 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 out_release;
+
+ 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->nrbufs = pipe->curbuf = 0;
+ file_accessed(in);
+ 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)
+ 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);
+}
+
+/**
+ * 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,
+ .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->nrbufs != pipe->buffers)
+ return 0;
+ if (flags & SPLICE_F_NONBLOCK)
+ return -EAGAIN;
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ pipe->waiting_writers++;
+ pipe_wait(pipe);
+ pipe->waiting_writers--;
+ }
+}
+
+static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
+ struct pipe_inode_info *opipe,
+ size_t len, unsigned int flags);
+
+/*
+ * 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 *ipipe;
+ struct pipe_inode_info *opipe;
+ loff_t offset;
+ long ret;
+
+ ipipe = get_pipe_info(in);
+ opipe = get_pipe_info(out);
+
+ if (ipipe && opipe) {
+ if (off_in || off_out)
+ return -ESPIPE;
+
+ if (!(in->f_mode & FMODE_READ))
+ return -EBADF;
+
+ if (!(out->f_mode & FMODE_WRITE))
+ return -EBADF;
+
+ /* Splicing to self would be fun, but... */
+ if (ipipe == opipe)
+ return -EINVAL;
+
+ 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;
+ if (copy_from_user(&offset, off_out, sizeof(loff_t)))
+ return -EFAULT;
+ } else {
+ offset = out->f_pos;
+ }
+
+ if (unlikely(!(out->f_mode & FMODE_WRITE)))
+ return -EBADF;
+
+ if (unlikely(out->f_flags & O_APPEND))
+ return -EINVAL;
+
+ ret = rw_verify_area(WRITE, out, &offset, len);
+ if (unlikely(ret < 0))
+ return ret;
+
+ 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 if (copy_to_user(off_out, &offset, sizeof(loff_t)))
+ ret = -EFAULT;
+
+ return ret;
+ }
+
+ if (opipe) {
+ if (off_out)
+ return -ESPIPE;
+ if (off_in) {
+ if (!(in->f_mode & FMODE_PREAD))
+ return -EINVAL;
+ if (copy_from_user(&offset, off_in, sizeof(loff_t)))
+ return -EFAULT;
+ } else {
+ offset = in->f_pos;
+ }
+
+ 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);
+ if (!off_in)
+ in->f_pos = offset;
+ else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
+ ret = -EFAULT;
+
+ return ret;
+ }
+
+ return -EINVAL;
+}
+
+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;
+ bool failed = false;
+
+ while (iov_iter_count(from) && !failed) {
+ struct page *pages[16];
+ ssize_t copied;
+ size_t start;
+ int n;
+
+ copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
+ if (copied <= 0) {
+ ret = copied;
+ break;
+ }
+
+ for (n = 0; copied; n++, start = 0) {
+ int size = min_t(int, copied, PAGE_SIZE - start);
+ if (!failed) {
+ buf.page = pages[n];
+ buf.offset = start;
+ buf.len = size;
+ ret = add_to_pipe(pipe, &buf);
+ if (unlikely(ret < 0)) {
+ failed = true;
+ } else {
+ iov_iter_advance(from, ret);
+ total += ret;
+ }
+ } else {
+ put_page(pages[n]);
+ }
+ copied -= size;
+ }
+ }
+ 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);
+ 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);
+ 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 = WRITE;
+ } else if (f.file->f_mode & FMODE_READ) {
+ *type = READ;
+ } 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().
+ *
+ */
+static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
+{
+ if (unlikely(flags & ~SPLICE_F_ALL))
+ return -EINVAL;
+
+ if (!iov_iter_count(iter))
+ return 0;
+
+ if (iov_iter_rw(iter) == WRITE)
+ return vmsplice_to_pipe(f, iter, flags);
+ else
+ return vmsplice_to_user(f, iter, flags);
+}
+
+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;
+ long error;
+ struct fd f;
+ int type;
+
+ 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) {
+ error = do_vmsplice(f.file, &iter, flags);
+ kfree(iov);
+ }
+ fdput(f);
+ return error;
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
+ unsigned int, nr_segs, unsigned int, flags)
+{
+ struct iovec iovstack[UIO_FASTIOV];
+ struct iovec *iov = iovstack;
+ struct iov_iter iter;
+ long error;
+ struct fd f;
+ int type;
+
+ f = fdget(fd);
+ error = vmsplice_type(f, &type);
+ if (error)
+ return error;
+
+ error = compat_import_iovec(type, iov32, nr_segs,
+ ARRAY_SIZE(iovstack), &iov, &iter);
+ if (!error) {
+ error = do_vmsplice(f.file, &iter, flags);
+ kfree(iov);
+ }
+ fdput(f);
+ return error;
+}
+#endif
+
+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) {
+ if (in.file->f_mode & FMODE_READ) {
+ out = fdget(fd_out);
+ if (out.file) {
+ if (out.file->f_mode & FMODE_WRITE)
+ 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 ->nrbufs without the inode lock first. This function
+ * is speculative anyways, so missing one is ok.
+ */
+ if (pipe->nrbufs)
+ return 0;
+
+ ret = 0;
+ pipe_lock(pipe);
+
+ 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);
+ }
+
+ 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 ->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;
+ pipe_lock(pipe);
+
+ 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--;
+ }
+
+ 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;
+ int ret = 0, nbuf;
+ 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);
+
+ do {
+ if (!opipe->readers) {
+ send_sig(SIGPIPE, current, 0);
+ if (!ret)
+ ret = -EPIPE;
+ break;
+ }
+
+ if (!ipipe->nrbufs && !ipipe->writers)
+ break;
+
+ /*
+ * Cannot make any progress, because either the input
+ * pipe is empty or the output pipe is full.
+ */
+ if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
+ /* 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 + ipipe->curbuf;
+ nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
+ obuf = opipe->bufs + nbuf;
+
+ if (len >= ibuf->len) {
+ /*
+ * Simply move the whole buffer from ipipe to opipe
+ */
+ *obuf = *ibuf;
+ ibuf->ops = NULL;
+ opipe->nrbufs++;
+ ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
+ ipipe->nrbufs--;
+ input_wakeup = true;
+ } else {
+ /*
+ * Get a reference to this pipe buffer,
+ * so we can copy the contents over.
+ */
+ pipe_buf_get(ipipe, ibuf);
+ *obuf = *ibuf;
+
+ /*
+ * Don't inherit the gift flag, we need to
+ * prevent multiple steals of this page.
+ */
+ obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+
+ obuf->len = len;
+ opipe->nrbufs++;
+ ibuf->offset += obuf->len;
+ ibuf->len -= obuf->len;
+ }
+ ret += obuf->len;
+ len -= obuf->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;
+ int ret = 0, i = 0, nbuf;
+
+ /*
+ * 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);
+
+ 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 >= opipe->buffers)
+ break;
+
+ ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
+ nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
+
+ /*
+ * Get a reference to this pipe buffer,
+ * so we can copy the contents over.
+ */
+ pipe_buf_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);
+
+ /*
+ * return EAGAIN if we have the potential of some data in the
+ * future, otherwise just return 0
+ */
+ if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
+ ret = -EAGAIN;
+
+ 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.
+ */
+static long do_tee(struct file *in, struct file *out, size_t len,
+ unsigned int flags)
+{
+ struct pipe_inode_info *ipipe = get_pipe_info(in);
+ struct pipe_inode_info *opipe = get_pipe_info(out);
+ 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 = 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;
+ int error;
+
+ if (unlikely(flags & ~SPLICE_F_ALL))
+ return -EINVAL;
+
+ if (unlikely(!len))
+ return 0;
+
+ error = -EBADF;
+ in = fdget(fdin);
+ if (in.file) {
+ if (in.file->f_mode & FMODE_READ) {
+ struct fd out = fdget(fdout);
+ if (out.file) {
+ if (out.file->f_mode & FMODE_WRITE)
+ error = do_tee(in.file, out.file,
+ len, flags);
+ fdput(out);
+ }
+ }
+ fdput(in);
+ }
+
+ return error;
+}