blob: ec8b54b5c0d28f52695ffbd829a5c267cae6fc90 [file] [log] [blame]
/*
* "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, 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(KERNEL_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, 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, 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;
WARN_ON_ONCE(pipe->nrbufs != 0);
while (len) {
size_t read_len;
loff_t pos = sd->pos, prev_pos = pos;
/* Don't try to read more the pipe has space for. */
read_len = min_t(size_t, len,
(pipe->buffers - pipe->nrbufs) << PAGE_SHIFT);
ret = do_splice_to(in, &pos, pipe, read_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;
}