Commit 5274f052 authored by Jens Axboe's avatar Jens Axboe Committed by Linus Torvalds
Browse files

[PATCH] Introduce sys_splice() system call



This adds support for the sys_splice system call. Using a pipe as a
transport, it can connect to files or sockets (latter as output only).

From the splice.c comments:

   "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 and fixing the initial implementation
   bugs.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5d4fe2c1
......@@ -312,3 +312,4 @@ ENTRY(sys_call_table)
.long sys_unshare /* 310 */
.long sys_set_robust_list
.long sys_get_robust_list
.long sys_splice
......@@ -1605,5 +1605,6 @@ sys_call_table:
data8 sys_ni_syscall // reserved for pselect
data8 sys_ni_syscall // 1295 reserved for ppoll
data8 sys_unshare
data8 sys_splice
.org sys_call_table + 8*NR_syscalls // guard against failures to increase NR_syscalls
......@@ -10,7 +10,7 @@ obj-y := open.o read_write.o file_table.o buffer.o bio.o super.o \
ioctl.o readdir.o select.o fifo.o locks.o dcache.o inode.o \
attr.o bad_inode.o file.o filesystems.o namespace.o aio.o \
seq_file.o xattr.o libfs.o fs-writeback.o mpage.o direct-io.o \
ioprio.o pnode.o drop_caches.o
ioprio.o pnode.o drop_caches.o splice.o
obj-$(CONFIG_INOTIFY) += inotify.o
obj-$(CONFIG_EPOLL) += eventpoll.o
......
......@@ -53,6 +53,8 @@ const struct file_operations ext2_file_operations = {
.readv = generic_file_readv,
.writev = generic_file_writev,
.sendfile = generic_file_sendfile,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
};
#ifdef CONFIG_EXT2_FS_XIP
......
......@@ -119,6 +119,8 @@ const struct file_operations ext3_file_operations = {
.release = ext3_release_file,
.fsync = ext3_sync_file,
.sendfile = generic_file_sendfile,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
};
struct inode_operations ext3_file_inode_operations = {
......
......@@ -15,6 +15,7 @@
#include <linux/pipe_fs_i.h>
#include <linux/uio.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>
......@@ -94,11 +95,20 @@ static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buff
{
struct page *page = buf->page;
if (info->tmp_page) {
__free_page(page);
/*
* If nobody else uses this page, and we don't already have a
* temporary page, let's keep track of it as a one-deep
* allocation cache
*/
if (page_count(page) == 1 && !info->tmp_page) {
info->tmp_page = page;
return;
}
info->tmp_page = page;
/*
* Otherwise just release our reference to it
*/
page_cache_release(page);
}
static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf)
......@@ -152,6 +162,11 @@ pipe_readv(struct file *filp, const struct iovec *_iov,
chars = total_len;
addr = ops->map(filp, info, buf);
if (IS_ERR(addr)) {
if (!ret)
ret = PTR_ERR(addr);
break;
}
error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
ops->unmap(info, buf);
if (unlikely(error)) {
......@@ -254,8 +269,16 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
struct pipe_buf_operations *ops = buf->ops;
int offset = buf->offset + buf->len;
if (ops->can_merge && offset + chars <= PAGE_SIZE) {
void *addr = ops->map(filp, info, buf);
int error = pipe_iov_copy_from_user(offset + addr, iov, chars);
void *addr;
int error;
addr = ops->map(filp, info, buf);
if (IS_ERR(addr)) {
error = PTR_ERR(addr);
goto out;
}
error = pipe_iov_copy_from_user(offset + addr, iov,
chars);
ops->unmap(info, buf);
ret = error;
do_wakeup = 1;
......
......@@ -1576,6 +1576,8 @@ const struct file_operations reiserfs_file_operations = {
.sendfile = generic_file_sendfile,
.aio_read = generic_file_aio_read,
.aio_write = reiserfs_aio_write,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
};
struct inode_operations reiserfs_file_inode_operations = {
......
/*
* "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 and fixing the initial implementation
* bugs.
*
* Copyright (C) 2005 Jens Axboe <axboe@suse.de>
* Copyright (C) 2005 Linus Torvalds <torvalds@osdl.org>
*
*/
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/pipe_fs_i.h>
#include <linux/mm_inline.h>
/*
* Passed to the actors
*/
struct splice_desc {
unsigned int len, total_len; /* current and remaining length */
unsigned int flags; /* splice flags */
struct file *file; /* file to read/write */
loff_t pos; /* file position */
};
static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
page_cache_release(buf->page);
buf->page = NULL;
}
static void *page_cache_pipe_buf_map(struct file *file,
struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
struct page *page = buf->page;
lock_page(page);
if (!PageUptodate(page)) {
unlock_page(page);
return ERR_PTR(-EIO);
}
if (!page->mapping) {
unlock_page(page);
return ERR_PTR(-ENODATA);
}
return kmap(buf->page);
}
static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
unlock_page(buf->page);
kunmap(buf->page);
}
static struct pipe_buf_operations page_cache_pipe_buf_ops = {
.can_merge = 0,
.map = page_cache_pipe_buf_map,
.unmap = page_cache_pipe_buf_unmap,
.release = page_cache_pipe_buf_release,
};
static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
int nr_pages, unsigned long offset,
unsigned long len)
{
struct pipe_inode_info *info;
int ret, do_wakeup, i;
ret = 0;
do_wakeup = 0;
i = 0;
mutex_lock(PIPE_MUTEX(*inode));
info = inode->i_pipe;
for (;;) {
int bufs;
if (!PIPE_READERS(*inode)) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
bufs = info->nrbufs;
if (bufs < PIPE_BUFFERS) {
int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS - 1);
struct pipe_buffer *buf = info->bufs + newbuf;
struct page *page = pages[i++];
unsigned long this_len;
this_len = PAGE_CACHE_SIZE - offset;
if (this_len > len)
this_len = len;
buf->page = page;
buf->offset = offset;
buf->len = this_len;
buf->ops = &page_cache_pipe_buf_ops;
info->nrbufs = ++bufs;
do_wakeup = 1;
ret += this_len;
len -= this_len;
offset = 0;
if (!--nr_pages)
break;
if (!len)
break;
if (bufs < PIPE_BUFFERS)
continue;
break;
}
if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}
if (do_wakeup) {
wake_up_interruptible_sync(PIPE_WAIT(*inode));
kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO,
POLL_IN);
do_wakeup = 0;
}
PIPE_WAITING_WRITERS(*inode)++;
pipe_wait(inode);
PIPE_WAITING_WRITERS(*inode)--;
}
mutex_unlock(PIPE_MUTEX(*inode));
if (do_wakeup) {
wake_up_interruptible(PIPE_WAIT(*inode));
kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN);
}
while (i < nr_pages)
page_cache_release(pages[i++]);
return ret;
}
static int __generic_file_splice_read(struct file *in, struct inode *pipe,
size_t len)
{
struct address_space *mapping = in->f_mapping;
unsigned int offset, nr_pages;
struct page *pages[PIPE_BUFFERS], *shadow[PIPE_BUFFERS];
struct page *page;
pgoff_t index, pidx;
int i, j;
index = in->f_pos >> PAGE_CACHE_SHIFT;
offset = in->f_pos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (nr_pages > PIPE_BUFFERS)
nr_pages = PIPE_BUFFERS;
/*
* initiate read-ahead on this page range
*/
do_page_cache_readahead(mapping, in, index, nr_pages);
/*
* Get as many pages from the page cache as possible..
* Start IO on the page cache entries we create (we
* can assume that any pre-existing ones we find have
* already had IO started on them).
*/
i = find_get_pages(mapping, index, nr_pages, pages);
/*
* common case - we found all pages and they are contiguous,
* kick them off
*/
if (i && (pages[i - 1]->index == index + i - 1))
goto splice_them;
/*
* fill shadow[] with pages at the right locations, so we only
* have to fill holes
*/
memset(shadow, 0, i * sizeof(struct page *));
for (j = 0, pidx = index; j < i; pidx++, j++)
shadow[pages[j]->index - pidx] = pages[j];
/*
* now fill in the holes
*/
for (i = 0, pidx = index; i < nr_pages; pidx++, i++) {
int error;
if (shadow[i])
continue;
/*
* no page there, look one up / create it
*/
page = find_or_create_page(mapping, pidx,
mapping_gfp_mask(mapping));
if (!page)
break;
if (PageUptodate(page))
unlock_page(page);
else {
error = mapping->a_ops->readpage(in, page);
if (unlikely(error)) {
page_cache_release(page);
break;
}
}
shadow[i] = page;
}
if (!i) {
for (i = 0; i < nr_pages; i++) {
if (shadow[i])
page_cache_release(shadow[i]);
}
return 0;
}
memcpy(pages, shadow, i * sizeof(struct page *));
/*
* Now we splice them into the pipe..
*/
splice_them:
return move_to_pipe(pipe, pages, i, offset, len);
}
ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
size_t len, unsigned int flags)
{
ssize_t spliced;
int ret;
ret = 0;
spliced = 0;
while (len) {
ret = __generic_file_splice_read(in, pipe, len);
if (ret <= 0)
break;
in->f_pos += ret;
len -= ret;
spliced += ret;
}
if (spliced)
return spliced;
return ret;
}
/*
* Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
*/
static int pipe_to_sendpage(struct pipe_inode_info *info,
struct pipe_buffer *buf, struct splice_desc *sd)
{
struct file *file = sd->file;
loff_t pos = sd->pos;
unsigned int offset;
ssize_t ret;
void *ptr;
/*
* sub-optimal, but we are limited by the pipe ->map. we don't
* need a kmap'ed buffer here, we just want to make sure we
* have the page pinned if the pipe page originates from the
* page cache
*/
ptr = buf->ops->map(file, info, buf);
if (IS_ERR(ptr))
return PTR_ERR(ptr);
offset = pos & ~PAGE_CACHE_MASK;
ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
sd->len < sd->total_len);
buf->ops->unmap(info, buf);
if (ret == sd->len)
return 0;
return -EIO;
}
/*
* 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.
*
* For now we just do the slower thing and always copy pages over, it's
* easier than migrating pages from the pipe to the target file. For the
* case of doing file | file splicing, the migrate approach had some LRU
* nastiness...
*/
static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
struct splice_desc *sd)
{
struct file *file = sd->file;
struct address_space *mapping = file->f_mapping;
unsigned int offset;
struct page *page;
char *src, *dst;
pgoff_t index;
int ret;
/*
* after this, page will be locked and unmapped
*/
src = buf->ops->map(file, info, buf);
if (IS_ERR(src))
return PTR_ERR(src);
index = sd->pos >> PAGE_CACHE_SHIFT;
offset = sd->pos & ~PAGE_CACHE_MASK;
find_page:
ret = -ENOMEM;
page = find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
if (!page)
goto out;
/*
* If the page is uptodate, it is also locked. If it isn't
* uptodate, we can mark it uptodate if we are filling the
* full page. Otherwise we need to read it in first...
*/
if (!PageUptodate(page)) {
if (sd->len < PAGE_CACHE_SIZE) {
ret = mapping->a_ops->readpage(file, page);
if (unlikely(ret))
goto out;
lock_page(page);
if (!PageUptodate(page)) {
/*
* page got invalidated, repeat
*/
if (!page->mapping) {
unlock_page(page);
page_cache_release(page);
goto find_page;
}
ret = -EIO;
goto out;
}
} else {
WARN_ON(!PageLocked(page));
SetPageUptodate(page);
}
}
ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
if (ret)
goto out;
dst = kmap_atomic(page, KM_USER0);
memcpy(dst + offset, src + buf->offset, sd->len);
flush_dcache_page(page);
kunmap_atomic(dst, KM_USER0);
ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
if (ret < 0)
goto out;
set_page_dirty(page);
ret = write_one_page(page, 0);
out:
if (ret < 0)
unlock_page(page);
page_cache_release(page);
buf->ops->unmap(info, buf);
return ret;
}
typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
struct splice_desc *);
static ssize_t move_from_pipe(struct inode *inode, struct file *out,
size_t len, unsigned int flags,
splice_actor *actor)
{
struct pipe_inode_info *info;
int ret, do_wakeup, err;
struct splice_desc sd;
ret = 0;
do_wakeup = 0;
sd.total_len = len;
sd.flags = flags;
sd.file = out;
sd.pos = out->f_pos;
mutex_lock(PIPE_MUTEX(*inode));
info = inode->i_pipe;
for (;;) {
int bufs = info->nrbufs;
if (bufs) {
int curbuf = info->curbuf;
struct pipe_buffer *buf = info->bufs + curbuf;
struct pipe_buf_operations *ops = buf->ops;
sd.len = buf->len;
if (sd.len > sd.total_len)
sd.len = sd.total_len;
err = actor(info, buf, &sd);
if (err) {
if (!ret && err != -ENODATA)
ret = err;
break;
}
ret += sd.len;
buf->offset += sd.len;
buf->len -= sd.len;
if (!buf->len) {
buf->ops = NULL;
ops->release(info, buf);
curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
info->curbuf = curbuf;
info->nrbufs = --bufs;
do_wakeup = 1;
}
sd.pos += sd.len;
sd.total_len -= sd.len;
if (!sd.total_len)
break;
}
if (bufs)
continue;
if (!PIPE_WRITERS(*inode))
break;
if (!PIPE_WAITING_WRITERS(*inode)) {
if (ret)
break;
}
if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}
if (do_wakeup) {
wake_up_interruptible_sync(PIPE_WAIT(*inode));
kill_fasync(PIPE_FASYNC_WRITERS(*inode),SIGIO,POLL_OUT);
do_wakeup = 0;
}
pipe_wait(inode);
}
mutex_unlock(PIPE_MUTEX(*inode));
if (do_wakeup) {
wake_up_interruptible(PIPE_WAIT(*inode));
kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
}
mutex_lock(&out->f_mapping->host->i_mutex);
out->f_pos = sd.pos;
mutex_unlock(&out->f_mapping->host->i_mutex);
return ret;
}
ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
size_t len, unsigned int flags)
{
return move_from_pipe(inode, out, len, flags, pipe_to_file);
}
ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,