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[PATCH] Add support for the sys_vmsplice syscall 

sys_splice() moves data to/from pipes with a file input/output. sys_vmsplice()
moves data to a pipe, with the input being a user address range instead.

This uses an approach suggested by Linus, where we can hold partial ranges
inside the pages[] map. Hopefully this will be useful for network
receive support as well.

Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-04-26 10:59:21 +02:00
parent 016b661e2f
commit 912d35f867
9 changed files with 268 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/ia64/kernel/entry.S
View File

@ -1610,5 +1610,6 @@ sys_call_table:
data8 sys_get_robust_list
data8 sys_sync_file_range // 1300
data8 sys_tee
data8 sys_vmsplice
.org sys_call_table + 8*NR_syscalls // guard against failures to increase NR_syscalls

1
arch/powerpc/kernel/systbl.S
View File

@ -324,6 +324,7 @@ COMPAT_SYS(ppoll)
SYSCALL(unshare)
SYSCALL(splice)
SYSCALL(tee)
SYSCALL(vmsplice)
/*
* please add new calls to arch/powerpc/platforms/cell/spu_callbacks.c

1
arch/powerpc/platforms/cell/spu_callbacks.c
View File

@ -318,6 +318,7 @@ void *spu_syscall_table[] = {
[__NR_unshare] sys_unshare,
[__NR_splice] sys_splice,
[__NR_tee] sys_tee,
[__NR_vmsplice] sys_vmsplice,
};
long spu_sys_callback(struct spu_syscall_block *s)

292
fs/splice.c
View File

@ -27,6 +27,7 @@
#include <linux/buffer_head.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/uio.h>
/*
* Passed to the actors
@ -38,6 +39,22 @@ struct splice_desc {
loff_t pos; /* file position */
};
struct partial_page {
unsigned int offset;
unsigned int len;
};
/*
* Passed to move_to_pipe
*/
struct splice_pipe_desc {
struct page **pages; /* page map */
struct partial_page *partial; /* pages[] may not be contig */
int nr_pages; /* number of pages in map */
unsigned int flags; /* splice flags */
struct pipe_buf_operations *ops;/* ops associated with output pipe */
};
/*
* 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
@ -128,6 +145,19 @@ static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
kunmap(buf->page);
}
static void *user_page_pipe_buf_map(struct file *file,
struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
return kmap(buf->page);
}
static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
kunmap(buf->page);
}
static void page_cache_pipe_buf_get(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
@ -143,19 +173,33 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = {
.get = page_cache_pipe_buf_get,
};
static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
return 1;
}
static struct pipe_buf_operations user_page_pipe_buf_ops = {
.can_merge = 0,
.map = user_page_pipe_buf_map,
.unmap = user_page_pipe_buf_unmap,
.release = page_cache_pipe_buf_release,
.steal = user_page_pipe_buf_steal,
.get = page_cache_pipe_buf_get,
};
/*
* Pipe output worker. This sets up our pipe format with the page cache
* pipe buffer operations. Otherwise very similar to the regular pipe_writev().
*/
static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
int nr_pages, unsigned long len,
unsigned int offset, unsigned int flags)
static ssize_t move_to_pipe(struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd)
{
int ret, do_wakeup, i;
int ret, do_wakeup, page_nr;
ret = 0;
do_wakeup = 0;
i = 0;
page_nr = 0;
if (pipe->inode)
mutex_lock(&pipe->inode->i_mutex);
@ -171,27 +215,19 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
if (pipe->nrbufs < PIPE_BUFFERS) {
int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
struct pipe_buffer *buf = pipe->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;
buf->page = spd->pages[page_nr];
buf->offset = spd->partial[page_nr].offset;
buf->len = spd->partial[page_nr].len;
buf->ops = spd->ops;
pipe->nrbufs++;
page_nr++;
ret += buf->len;
if (pipe->inode)
do_wakeup = 1;
ret += this_len;
len -= this_len;
offset = 0;
if (!--nr_pages)
break;
if (!len)
if (!--spd->nr_pages)
break;
if (pipe->nrbufs < PIPE_BUFFERS)
continue;
@ -199,7 +235,7 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
break;
}
if (flags & SPLICE_F_NONBLOCK) {
if (spd->flags & SPLICE_F_NONBLOCK) {
if (!ret)
ret = -EAGAIN;
break;
@ -234,8 +270,8 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}
while (i < nr_pages)
page_cache_release(pages[i++]);
while (page_nr < spd->nr_pages)
page_cache_release(spd->pages[page_nr++]);
return ret;
}
@ -246,17 +282,24 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
unsigned int flags)
{
struct address_space *mapping = in->f_mapping;
unsigned int loff, offset, nr_pages;
unsigned int loff, nr_pages;
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
size_t bytes;
int i, error;
size_t total_len;
int error;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
};
index = *ppos >> PAGE_CACHE_SHIFT;
loff = offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (nr_pages > PIPE_BUFFERS)
nr_pages = PIPE_BUFFERS;
@ -266,15 +309,15 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
* read-ahead if this is a non-zero offset (we are likely doing small
* chunk splice and the page is already there) for a single page.
*/
if (!offset || nr_pages > 1)
do_page_cache_readahead(mapping, in, index, nr_pages);
if (!loff || spd.nr_pages > 1)
do_page_cache_readahead(mapping, in, index, spd.nr_pages);
/*
* Now fill in the holes:
*/
error = 0;
bytes = 0;
for (i = 0; i < nr_pages; i++, index++) {
total_len = 0;
for (spd.nr_pages = 0; spd.nr_pages < nr_pages; spd.nr_pages++, index++) {
unsigned int this_len;
if (!len)
@ -367,26 +410,29 @@ readpage:
*/
if (end_index == index) {
loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
if (bytes + loff > isize) {
if (total_len + loff > isize) {
page_cache_release(page);
break;
}
/*
* force quit after adding this page
*/
nr_pages = i;
nr_pages = spd.nr_pages;
this_len = min(this_len, loff);
loff = 0;
}
}
fill_it:
pages[i] = page;
bytes += this_len;
pages[spd.nr_pages] = page;
partial[spd.nr_pages].offset = loff;
partial[spd.nr_pages].len = this_len;
len -= this_len;
total_len += this_len;
loff = 0;
}
if (i)
return move_to_pipe(pipe, pages, i, bytes, offset, flags);
if (spd.nr_pages)
return move_to_pipe(pipe, &spd);
return error;
}
@ -1018,6 +1064,174 @@ static long do_splice(struct file *in, loff_t __user *off_in,
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)
{
int buffers = 0, error = 0;
/*
* It's ok to take the mmap_sem for reading, even
* across a "get_user()".
*/
down_read(&current->mm->mmap_sem);
while (nr_vecs) {
unsigned long off, npages;
void __user *base;
size_t len;
int i;
/*
* 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;
error = -EFAULT;
if (unlikely(!base))
break;
/*
* Get this base offset and number of pages, then map
* in the user pages.
*/
off = (unsigned long) base & ~PAGE_MASK;
npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (npages > PIPE_BUFFERS - buffers)
npages = PIPE_BUFFERS - buffers;
error = get_user_pages(current, current->mm,
(unsigned long) base, npages, 0, 0,
&pages[buffers], NULL);
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++;
}
up_read(&current->mm->mmap_sem);
if (buffers)
return buffers;
return error;
}
/*
* 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.
*
* Note that vmsplice only supports 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).
*
* Alas, it isn't here.
*
*/
static long do_vmsplice(struct file *file, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe = file->f_dentry->d_inode->i_pipe;
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.flags = flags,
.ops = &user_page_pipe_buf_ops,
};
if (unlikely(!pipe))
return -EBADF;
if (unlikely(nr_segs > UIO_MAXIOV))
return -EINVAL;
else if (unlikely(!nr_segs))
return 0;
spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial);
if (spd.nr_pages <= 0)
return spd.nr_pages;
return move_to_pipe(pipe, &spd);
}
asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags)
{
struct file *file;
long error;
int fput;
error = -EBADF;
file = fget_light(fd, &fput);
if (file) {
if (file->f_mode & FMODE_WRITE)
error = do_vmsplice(file, iov, nr_segs, flags);
fput_light(file, fput);
}
return error;
}
asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
int fd_out, loff_t __user *off_out,
size_t len, unsigned int flags)

3
include/asm-i386/unistd.h
View File

@ -321,8 +321,9 @@
#define __NR_splice 313
#define __NR_sync_file_range 314
#define __NR_tee 315
#define __NR_vmsplice 316
#define NR_syscalls 316
#define NR_syscalls 317
/*
* user-visible error numbers are in the range -1 - -128: see

3
include/asm-ia64/unistd.h
View File

@ -290,12 +290,13 @@
#define __NR_get_robust_list 1299
#define __NR_sync_file_range 1300
#define __NR_tee 1301
#define __NR_vmsplice 1302
#ifdef __KERNEL__
#include <linux/config.h>
#define NR_syscalls 278 /* length of syscall table */
#define NR_syscalls 279 /* length of syscall table */
#define __ARCH_WANT_SYS_RT_SIGACTION

3
include/asm-powerpc/unistd.h
View File

@ -303,8 +303,9 @@
#define __NR_unshare 282
#define __NR_splice 283
#define __NR_tee 284
#define __NR_vmsplice 285
#define __NR_syscalls 285
#define __NR_syscalls 286
#ifdef __KERNEL__
#define __NR__exit __NR_exit

4
include/asm-x86_64/unistd.h
View File

@ -615,8 +615,10 @@ __SYSCALL(__NR_splice, sys_splice)
__SYSCALL(__NR_tee, sys_tee)
#define __NR_sync_file_range 277
__SYSCALL(__NR_sync_file_range, sys_sync_file_range)
#define __NR_vmsplice 278
__SYSCALL(__NR_vmsplice, sys_vmsplice)
#define __NR_syscall_max __NR_sync_file_range
#define __NR_syscall_max __NR_vmsplice
#ifndef __NO_STUBS

3
include/linux/syscalls.h
View File

@ -574,6 +574,9 @@ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
int fd_out, loff_t __user *off_out,
size_t len, unsigned int flags);
asmlinkage long sys_vmsplice(int fd, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags);
asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags);
asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,