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/*
* "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/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>

/*
* 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)
{
page_cache_release(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,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.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,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.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, do_wakeup, page_nr;

ret = 0;
do_wakeup = 0;
page_nr = 0;

pipe_lock(pipe);

for (;;) {
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}

if (pipe->nrbufs < pipe->buffers) {
int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
struct pipe_buffer *buf = pipe->bufs + newbuf;

buf->page = spd->pages[page_nr];
buf->offset = spd->partial[page_nr].offset;
buf->len = spd->partial[page_nr].len;
buf->private = spd->partial[page_nr].private;
buf->ops = spd->ops;
if (spd->flags & SPLICE_F_GIFT)
buf->flags |= PIPE_BUF_FLAG_GIFT;

pipe->nrbufs++;
page_nr++;
ret += buf->len;

if (pipe->inode)
do_wakeup = 1;

if (!--spd->nr_pages)
break;
if (pipe->nrbufs < pipe->buffers)
continue;

break;
}

if (spd->flags & SPLICE_F_NONBLOCK) {
if (!ret)
ret = -EAGAIN;
break;
}

if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}

if (do_wakeup) {
smp_mb();
if (waitqueue_active(&pipe->wait))
wake_up_interruptible_sync(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
do_wakeup = 0;
}

pipe->waiting_writers++;
pipe_wait(pipe);
pipe->waiting_writers--;
}

pipe_unlock(pipe);

if (do_wakeup)
wakeup_pipe_readers(pipe);

while (page_nr < spd_pages)
spd->spd_release(spd, page_nr++);

return ret;
}

void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
{
page_cache_release(spd->pages[i]);
}

/*
* 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 = ACCESS_ONCE(pipe->buffers);

spd->nr_pages_max = buffers;
if (buffers <= PIPE_DEF_BUFFERS)
return 0;

spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
spd->partial = kmalloc(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);
}

static int
__generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct address_space *mapping = in->f_mapping;
unsigned int loff, nr_pages, req_pages;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
.spd_release = spd_release_page,
};

if (splice_grow_spd(pipe, &spd))
return -ENOMEM;

index = *ppos >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
nr_pages = min(req_pages, spd.nr_pages_max);

/*
* Lookup the (hopefully) full range of pages we need.
*/
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
index += spd.nr_pages;

/*
* If find_get_pages_contig() returned fewer pages than we needed,
* readahead/allocate the rest and fill in the holes.
*/
if (spd.nr_pages < nr_pages)
page_cache_sync_readahead(mapping, &in->f_ra, in,
index, req_pages - spd.nr_pages);

error = 0;
while (spd.nr_pages < nr_pages) {
/*
* Page could be there, find_get_pages_contig() breaks on
* the first hole.
*/
page = find_get_page(mapping, index);
if (!page) {
/*
* page didn't exist, allocate one.
*/
page = page_cache_alloc_cold(mapping);
if (!page)
break;

error = add_to_page_cache_lru(page, mapping, index,
GFP_KERNEL);
if (unlikely(error)) {
page_cache_release(page);
if (error == -EEXIST)
continue;
break;
}
/*
* add_to_page_cache() locks the page, unlock it
* to avoid convoluting the logic below even more.
*/
unlock_page(page);
}

spd.pages[spd.nr_pages++] = page;
index++;
}

/*
* Now loop over the map and see if we need to start IO on any
* pages, fill in the partial map, etc.
*/
index = *ppos >> PAGE_CACHE_SHIFT;
nr_pages = spd.nr_pages;
spd.nr_pages = 0;
for (page_nr = 0; page_nr < nr_pages; page_nr++) {
unsigned int this_len;

if (!len)
break;

/*
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
page = spd.pages[page_nr];

if (PageReadahead(page))
page_cache_async_readahead(mapping, &in->f_ra, in,
page, index, req_pages - page_nr);

/*
* If the page isn't uptodate, we may need to start io on it
*/
if (!PageUptodate(page)) {
lock_page(page);

/*
* Page was truncated, or invalidated by the
* filesystem. Redo the find/create, but this time the
* page is kept locked, so there's no chance of another
* race with truncate/invalidate.
*/
if (!page->mapping) {
unlock_page(page);
page = find_or_create_page(mapping, index,
mapping_gfp_mask(mapping));

if (!page) {
error = -ENOMEM;
break;
}
page_cache_release(spd.pages[page_nr]);
spd.pages[page_nr] = page;
}
/*
* page was already under io and is now done, great
*/
if (PageUptodate(page)) {
unlock_page(page);
goto fill_it;
}

/*
* need to read in the page
*/
error = mapping->a_ops->readpage(in, page);
if (unlikely(error)) {
/*
* We really should re-lookup the page here,
* but it complicates things a lot. Instead
* lets just do what we already stored, and
* we'll get it the next time we are called.
*/
if (error == AOP_TRUNCATED_PAGE)
error = 0;

break;
}
}
fill_it:
/*
* i_size must be checked after PageUptodate.
*/
isize = i_size_read(mapping->host);
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
if (unlikely(!isize || index > end_index))
break;

/*
* if this is the last page, see if we need to shrink
* the length and stop
*/
if (end_index == index) {
unsigned int plen;

/*
* max good bytes in this page
*/
plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
if (plen <= loff)
break;

/*
* force quit after adding this page
*/
this_len = min(this_len, plen - loff);
len = this_len;
}

spd.partial[page_nr].offset = loff;
spd.partial[page_nr].len = this_len;
len -= this_len;
loff = 0;
spd.nr_pages++;
index++;
}

/*
* Release any pages at the end, if we quit early. 'page_nr' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
page_cache_release(spd.pages[page_nr++]);
in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;

if (spd.nr_pages)
error = splice_to_pipe(pipe, &spd);

splice_shrink_spd(&spd);
return error;
}

/**
* 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 the address_space operations for the source implements
* a readpage() hook.
*
*/
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
loff_t isize, left;
int ret;

isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
return 0;

left = isize - *ppos;
if (unlikely(left < len))
len = left;

ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
if (ret > 0) {
*ppos += ret;
file_accessed(in);
}

return ret;
}
EXPORT_SYMBOL(generic_file_splice_read);

static const struct pipe_buf_operations default_pipe_buf_ops = {
.can_merge = 0,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_steal,
.get = generic_pipe_buf_get,
};

static ssize_t kernel_readv(struct file *file, const struct iovec *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);
set_fs(old_fs);

return res;
}

static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
loff_t pos)
{
mm_segment_t old_fs;
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_write(file, (const char __user *)buf, count, &pos);
set_fs(old_fs);

return res;
}

ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
unsigned int nr_pages;
unsigned int nr_freed;
size_t offset;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
ssize_t res;
size_t this_len;
int error;
int i;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &default_pipe_buf_ops,
.spd_release = spd_release_page,
};

if (splice_grow_spd(pipe, &spd))
return -ENOMEM;

res = -ENOMEM;
vec = __vec;
if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
if (!vec)
goto shrink_ret;
}

offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
struct page *page;

page = alloc_page(GFP_USER);
error = -ENOMEM;
if (!page)
goto err;

this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
vec[i].iov_base = (void __user *) page_address(page);
vec[i].iov_len = this_len;
spd.pages[i] = page;
spd.nr_pages++;
len -= this_len;
offset = 0;
}

res = kernel_readv(in, vec, spd.nr_pages, *ppos);
if (res < 0) {
error = res;
goto err;
}

error = 0;
if (!res)
goto err;

nr_freed = 0;
for (i = 0; i < spd.nr_pages; i++) {
this_len = min_t(size_t, vec[i].iov_len, res);
spd.partial[i].offset = 0;
spd.partial[i].len = this_len;
if (!this_len) {
__free_page(spd.pages[i]);
spd.pages[i] = NULL;
nr_freed++;
}
res -= this_len;
}
spd.nr_pages -= nr_freed;

res = splice_to_pipe(pipe, &spd);
if (res > 0)
*ppos += res;

shrink_ret:
if (vec != __vec)
kfree(vec);
splice_shrink_spd(&spd);
return res;

err:
for (i = 0; i < spd.nr_pages; i++)
__free_page(spd.pages[i]);

res = error;
goto shrink_ret;
}
EXPORT_SYMBOL(default_file_splice_read);

/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
*/
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
struct pipe_buffer *buf, struct splice_desc *sd)
{
struct file *file = sd->u.file;
loff_t pos = sd->pos;
int more;

if (!likely(file->f_op && file->f_op->sendpage))
return -EINVAL;

more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
if (sd->len < sd->total_len)
more |= MSG_SENDPAGE_NOTLAST;
return file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}

/*
* This is a little more tricky than the file -> pipe splicing. There are
* basically three cases:
*
* - Destination page already exists in the address space and there
* are users of it. For that case we have no other option that
* copying the data. Tough luck.
* - Destination page already exists in the address space, but there
* are no users of it. Make sure it's uptodate, then drop it. Fall
* through to last case.
* - Destination page does not exist, we can add the pipe page to
* the page cache and avoid the copy.
*
* If asked to move pages to the output file (SPLICE_F_MOVE is set in
* sd->flags), we attempt to migrate pages from the pipe to the output
* file address space page cache. This is possible if no one else has
* the pipe page referenced outside of the pipe and page cache. If
* SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
* a new page in the output file page cache and fill/dirty that.
*/
int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
struct file *file = sd->u.file;
struct address_space *mapping = file->f_mapping;
unsigned int offset, this_len;
struct page *page;
void *fsdata;
int ret;

offset = sd->pos & ~PAGE_CACHE_MASK;

this_len = sd->len;
if (this_len + offset > PAGE_CACHE_SIZE)
this_len = PAGE_CACHE_SIZE - offset;

ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
if (unlikely(ret))
goto out;

if (buf->page != page) {
char *src = buf->ops->map(pipe, buf, 1);
char *dst = kmap_atomic(page);

memcpy(dst + offset, src + buf->offset, this_len);
flush_dcache_page(page);
kunmap_atomic(dst);
buf->ops->unmap(pipe, buf, src);
}
ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
page, fsdata);
out:
return ret;
}
EXPORT_SYMBOL(pipe_to_file);

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.
*/
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;
const struct pipe_buf_operations *ops = buf->ops;

sd->len = buf->len;
if (sd->len > sd->total_len)
sd->len = sd->total_len;

ret = buf->ops->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) {
buf->ops = NULL;
ops->release(pipe, buf);
pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
pipe->nrbufs--;
if (pipe->inode)
sd->need_wakeup = true;
}

if (!sd->total_len)
return 0;
}

return 1;
}
EXPORT_SYMBOL(splice_from_pipe_feed);

/**
* 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.
*/
int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
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;
}
EXPORT_SYMBOL(splice_from_pipe_next);

/**
* 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.
*/
void splice_from_pipe_begin(struct splice_desc *sd)
{
sd->num_spliced = 0;
sd->need_wakeup = false;
}
EXPORT_SYMBOL(splice_from_pipe_begin);

/**
* 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().
*/
void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
if (sd->need_wakeup)
wakeup_pipe_writers(pipe);
}
EXPORT_SYMBOL(splice_from_pipe_end);

/**
* __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 {
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;
}

/**
* generic_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.
*
*/
ssize_t
generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
struct address_space *mapping = out->f_mapping;
struct inode *inode = mapping->host;
struct splice_desc sd = {
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.file = out,
};
ssize_t ret;

pipe_lock(pipe);

splice_from_pipe_begin(&sd);
do {
ret = splice_from_pipe_next(pipe, &sd);
if (ret <= 0)
break;

mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
ret = file_remove_suid(out);
if (!ret) {
ret = file_update_time(out);
if (!ret)
ret = splice_from_pipe_feed(pipe, &sd,
pipe_to_file);
}
mutex_unlock(&inode->i_mutex);
} while (ret > 0);
splice_from_pipe_end(pipe, &sd);

pipe_unlock(pipe);

if (sd.num_spliced)
ret = sd.num_spliced;

if (ret > 0) {
unsigned long nr_pages;
int err;

nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

err = generic_write_sync(out, *ppos, ret);
if (err)
ret = err;
else
*ppos += ret;
balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
}

return ret;
}

EXPORT_SYMBOL(generic_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;

data = buf->ops->map(pipe, buf, 0);
ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
buf->ops->unmap(pipe, buf, data);

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);
int 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, ppos, len);
if (unlikely(ret < 0))
return ret;

if (out->f_op && 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 (in->f_op && 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;

/*
* We require the input being a regular file, as we don't want to
* randomly drop data for eg socket -> socket splicing. Use the
* piped splicing for that!
*/
i_mode = in->f_path.dentry->d_inode->i_mode;
if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
return -EINVAL;

/*
* neither in nor out is a pipe, setup an internal pipe attached to
* 'out' and transfer the wanted data from 'in' to 'out' through that
*/
pipe = current->splice_pipe;
if (unlikely(!pipe)) {
pipe = alloc_pipe_info(NULL);
if (!pipe)
return -ENOMEM;

/*
* We don't have an immediate reader, but we'll read the stuff
* out of the pipe right after the splice_to_pipe(). So set
* PIPE_READERS appropriately.
*/
pipe->readers = 1;

current->splice_pipe = pipe;
}

/*
* Do the splice.
*/
ret = 0;
bytes = 0;
len = sd->total_len;
flags = sd->flags;

/*
* Don't block on output, we have to drain the direct pipe.
*/
sd->flags &= ~SPLICE_F_NONBLOCK;

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;

/*
* 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) {
buf->ops->release(pipe, buf);
buf->ops = NULL;
}
}

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, &file->f_pos, 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
* @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,
size_t len, unsigned int flags)
{
struct splice_desc sd = {
.len = len,
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.file = out,
};
long ret;

ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
if (ret > 0)
*ppos = sd.pos;

return ret;
}

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, *off;
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;
off = &offset;
} else
off = &out->f_pos;

ret = do_splice_from(ipipe, out, off, len, flags);

if (off_out && copy_to_user(off_out, off, 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;
off = &offset;
} else
off = &in->f_pos;

ret = do_splice_to(in, off, opipe, len, flags);

if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
ret = -EFAULT;

return ret;
}

return -EINVAL;
}

/*
* Map an iov into an array of pages and offset/length tupples. With the
* partial_page structure, we can map several non-contiguous ranges into
* our ones pages[] map instead of splitting that operation into pieces.
* Could easily be exported as a generic helper for other users, in which
* case one would probably want to add a 'max_nr_pages' parameter as well.
*/
static int get_iovec_page_array(const struct iovec __user *iov,
unsigned int nr_vecs, struct page **pages,
struct partial_page *partial, bool aligned,
unsigned int pipe_buffers)
{
int buffers = 0, error = 0;

while (nr_vecs) {
unsigned long off, npages;
struct iovec entry;
void __user *base;
size_t len;
int i;

error = -EFAULT;
if (copy_from_user(&entry, iov, sizeof(entry)))
break;

base = entry.iov_base;
len = entry.iov_len;

/*
* Sanity check this iovec. 0 read succeeds.
*/
error = 0;
if (unlikely(!len))
break;
error = -EFAULT;
if (!access_ok(VERIFY_READ, base, len))
break;

/*
* Get this base offset and number of pages, then map
* in the user pages.
*/
off = (unsigned long) base & ~PAGE_MASK;

/*
* If asked for alignment, the offset must be zero and the
* length a multiple of the PAGE_SIZE.
*/
error = -EINVAL;
if (aligned && (off || len & ~PAGE_MASK))
break;

npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (npages > pipe_buffers - buffers)
npages = pipe_buffers - buffers;

error = get_user_pages_fast((unsigned long)base, npages,
0, &pages[buffers]);

if (unlikely(error <= 0))
break;

/*
* Fill this contiguous range into the partial page map.
*/
for (i = 0; i < error; i++) {
const int plen = min_t(size_t, len, PAGE_SIZE - off);

partial[buffers].offset = off;
partial[buffers].len = plen;

off = 0;
len -= plen;
buffers++;
}

/*
* We didn't complete this iov, stop here since it probably
* means we have to move some of this into a pipe to
* be able to continue.
*/
if (len)
break;

/*
* Don't continue if we mapped fewer pages than we asked for,
* or if we mapped the max number of pages that we have
* room for.
*/
if (error < npages || buffers == pipe_buffers)
break;

nr_vecs--;
iov++;
}

if (buffers)
return buffers;

return error;
}

static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
char *src;
int ret;

/*
* See if we can use the atomic maps, by prefaulting in the
* pages and doing an atomic copy
*/
if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
src = buf->ops->map(pipe, buf, 1);
ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
sd->len);
buf->ops->unmap(pipe, buf, src);
if (!ret) {
ret = sd->len;
goto out;
}
}

/*
* No dice, use slow non-atomic map and copy
*/
src = buf->ops->map(pipe, buf, 0);

ret = sd->len;
if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
ret = -EFAULT;

buf->ops->unmap(pipe, buf, src);
out:
if (ret > 0)
sd->u.userptr += ret;
return ret;
}

/*
* 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, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe;
struct splice_desc sd;
ssize_t size;
int error;
long ret;

pipe = get_pipe_info(file);
if (!pipe)
return -EBADF;

pipe_lock(pipe);

error = ret = 0;
while (nr_segs) {
void __user *base;
size_t len;

/*
* Get user address base and length for this iovec.
*/
error = get_user(base, &iov->iov_base);
if (unlikely(error))
break;
error = get_user(len, &iov->iov_len);
if (unlikely(error))
break;

/*
* Sanity check this iovec. 0 read succeeds.
*/
if (unlikely(!len))
break;
if (unlikely(!base)) {
error = -EFAULT;
break;
}

if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
error = -EFAULT;
break;
}

sd.len = 0;
sd.total_len = len;
sd.flags = flags;
sd.u.userptr = base;
sd.pos = 0;

size = __splice_from_pipe(pipe, &sd, pipe_to_user);
if (size < 0) {
if (!ret)
ret = size;

break;
}

ret += size;

if (size < len)
break;

nr_segs--;
iov++;
}

pipe_unlock(pipe);

if (!ret)
ret = error;

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, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &user_page_pipe_buf_ops,
.spd_release = spd_release_page,
};
long ret;

pipe = get_pipe_info(file);
if (!pipe)
return -EBADF;

if (splice_grow_spd(pipe, &spd))
return -ENOMEM;

spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
spd.partial, false,
spd.nr_pages_max);
if (spd.nr_pages <= 0)
ret = spd.nr_pages;
else
ret = splice_to_pipe(pipe, &spd);

splice_shrink_spd(&spd);
return ret;
}

/*
* 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 *, iov,
unsigned long, nr_segs, unsigned int, flags)
{
struct file *file;
long error;
int fput;

if (unlikely(nr_segs > UIO_MAXIOV))
return -EINVAL;
else if (unlikely(!nr_segs))
return 0;

error = -EBADF;
file = fget_light(fd, &fput);
if (file) {
if (file->f_mode & FMODE_WRITE)
error = vmsplice_to_pipe(file, iov, nr_segs, flags);
else if (file->f_mode & FMODE_READ)
error = vmsplice_to_user(file, iov, nr_segs, flags);

fput_light(file, fput);
}

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)
{
long error;
struct file *in, *out;
int fput_in, fput_out;

if (unlikely(!len))
return 0;

error = -EBADF;
in = fget_light(fd_in, &fput_in);
if (in) {
if (in->f_mode & FMODE_READ) {
out = fget_light(fd_out, &fput_out);
if (out) {
if (out->f_mode & FMODE_WRITE)
error = do_splice(in, off_in,
out, off_out,
len, flags);
fput_light(out, fput_out);
}
}

fput_light(in, fput_in);
}

return error;
}

/*
* Make sure there's data to read. Wait for input if we can, otherwise
* return an appropriate error.
*/
static int 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.
*/
ibuf->ops->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.
*/
ibuf->ops->get(ipipe, ibuf);

obuf = opipe->bufs + nbuf;
*obuf = *ibuf;

/*
* Don't inherit the gift flag, we need to
* prevent multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;

if (obuf->len > len)
obuf->len = len;

opipe->nrbufs++;
ret += obuf->len;
len -= obuf->len;
i++;
} while (len);

/*
* 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 file *in;
int error, fput_in;

if (unlikely(!len))
return 0;

error = -EBADF;
in = fget_light(fdin, &fput_in);
if (in) {
if (in->f_mode & FMODE_READ) {
int fput_out;
struct file *out = fget_light(fdout, &fput_out);

if (out) {
if (out->f_mode & FMODE_WRITE)
error = do_tee(in, out, len, flags);
fput_light(out, fput_out);
}
}
  fput_light(in, fput_in);
  }

return error;
}
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