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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-25 05:34:00 +08:00
linux-next/fs/splice.c
Jens Axboe a0548871ed [PATCH] splice: redo page lookup if add_to_page_cache() returns -EEXIST
This can happen quite easily, if several processes are trying to splice
the same file at the same time. It's not a failure, it just means someone
raced with us in allocating this file page. So just dump the allocated
page and relookup the original.

Signed-off-by: Jens Axboe <axboe@suse.de>
2006-05-04 06:55:12 +02:00

1491 lines
34 KiB
C

/*
* "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@suse.de>
* 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/pipe_fs_i.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/uio.h>
struct partial_page {
unsigned int offset;
unsigned int len;
};
/*
* Passed to splice_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
* 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 = page_mapping(page);
lock_page(page);
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 (PagePrivate(page))
try_to_release_page(page, mapping_gfp_mask(mapping));
if (!remove_mapping(mapping, page)) {
unlock_page(page);
return 1;
}
buf->flags |= PIPE_BUF_FLAG_LRU;
return 0;
}
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;
}
static int page_cache_pipe_buf_pin(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;
}
static struct pipe_buf_operations page_cache_pipe_buf_ops = {
.can_merge = 0,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.pin = page_cache_pipe_buf_pin,
.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 struct pipe_buf_operations user_page_pipe_buf_ops = {
.can_merge = 0,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.pin = generic_pipe_buf_pin,
.release = page_cache_pipe_buf_release,
.steal = user_page_pipe_buf_steal,
.get = generic_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 splice_to_pipe(struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd)
{
int ret, do_wakeup, page_nr;
ret = 0;
do_wakeup = 0;
page_nr = 0;
if (pipe->inode)
mutex_lock(&pipe->inode->i_mutex);
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->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--;
}
if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);
if (do_wakeup) {
smp_mb();
if (waitqueue_active(&pipe->wait))
wake_up_interruptible(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}
while (page_nr < spd->nr_pages)
page_cache_release(spd->pages[page_nr++]);
return ret;
}
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;
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
size_t total_len;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
};
index = *ppos >> 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;
/*
* Initiate read-ahead on this page range. however, don't call into
* 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 (!loff || nr_pages > 1)
page_cache_readahead(mapping, &in->f_ra, in, index, nr_pages);
/*
* Now fill in the holes:
*/
error = 0;
total_len = 0;
/*
* Lookup the (hopefully) full range of pages we need.
*/
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, pages);
/*
* If find_get_pages_contig() returned fewer pages than we needed,
* allocate the rest.
*/
index += spd.nr_pages;
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) {
/*
* Make sure the read-ahead engine is notified
* about this failure.
*/
handle_ra_miss(mapping, &in->f_ra, index);
/*
* page didn't exist, allocate one.
*/
page = page_cache_alloc_cold(mapping);
if (!page)
break;
error = add_to_page_cache_lru(page, mapping, index,
mapping_gfp_mask(mapping));
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);
}
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 = pages[page_nr];
/*
* If the page isn't uptodate, we may need to start io on it
*/
if (!PageUptodate(page)) {
/*
* If in nonblock mode then dont block on waiting
* for an in-flight io page
*/
if (flags & SPLICE_F_NONBLOCK)
break;
lock_page(page);
/*
* page was truncated, stop here. if this isn't the
* first page, we'll just complete what we already
* added
*/
if (!page->mapping) {
unlock_page(page);
break;
}
/*
* 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;
}
/*
* i_size must be checked after ->readpage().
*/
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) {
loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
if (total_len + loff > isize)
break;
/*
* force quit after adding this page
*/
len = this_len;
this_len = min(this_len, loff);
loff = 0;
}
}
fill_it:
partial[page_nr].offset = loff;
partial[page_nr].len = this_len;
len -= this_len;
total_len += this_len;
loff = 0;
spd.nr_pages++;
index++;
}
/*
* Release any pages at the end, if we quit early. 'i' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
page_cache_release(pages[page_nr++]);
if (spd.nr_pages)
return splice_to_pipe(pipe, &spd);
return error;
}
/**
* generic_file_splice_read - splice data from file to a pipe
* @in: file to splice from
* @pipe: pipe to splice to
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Will read pages from given file and fill them into a pipe.
*/
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
ssize_t spliced;
int ret;
ret = 0;
spliced = 0;
while (len) {
ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
if (ret < 0)
break;
else if (!ret) {
if (spliced)
break;
if (flags & SPLICE_F_NONBLOCK) {
ret = -EAGAIN;
break;
}
}
*ppos += ret;
len -= ret;
spliced += ret;
}
if (spliced)
return spliced;
return ret;
}
EXPORT_SYMBOL(generic_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->file;
loff_t pos = sd->pos;
int ret, more;
ret = buf->ops->pin(pipe, buf);
if (!ret) {
more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
ret = file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}
return ret;
}
/*
* 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.
*/
static int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
struct file *file = sd->file;
struct address_space *mapping = file->f_mapping;
gfp_t gfp_mask = mapping_gfp_mask(mapping);
unsigned int offset, this_len;
struct page *page;
pgoff_t index;
int ret;
/*
* make sure the data in this buffer is uptodate
*/
ret = buf->ops->pin(pipe, buf);
if (unlikely(ret))
return ret;
index = sd->pos >> PAGE_CACHE_SHIFT;
offset = sd->pos & ~PAGE_CACHE_MASK;
this_len = sd->len;
if (this_len + offset > PAGE_CACHE_SIZE)
this_len = PAGE_CACHE_SIZE - offset;
/*
* Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full
* page.
*/
if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
/*
* If steal succeeds, buf->page is now pruned from the
* pagecache and we can reuse it. The page will also be
* locked on successful return.
*/
if (buf->ops->steal(pipe, buf))
goto find_page;
page = buf->page;
if (add_to_page_cache(page, mapping, index, gfp_mask)) {
unlock_page(page);
goto find_page;
}
page_cache_get(page);
if (!(buf->flags & PIPE_BUF_FLAG_LRU))
lru_cache_add(page);
} else {
find_page:
page = find_lock_page(mapping, index);
if (!page) {
ret = -ENOMEM;
page = page_cache_alloc_cold(mapping);
if (unlikely(!page))
goto out_nomem;
/*
* This will also lock the page
*/
ret = add_to_page_cache_lru(page, mapping, index,
gfp_mask);
if (unlikely(ret))
goto out;
}
/*
* We get here with the page locked. If the page is also
* uptodate, we don't need to do more. If it isn't, we
* may need to bring it in if we are not going to overwrite
* the full page.
*/
if (!PageUptodate(page)) {
if (this_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
SetPageUptodate(page);
}
}
ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
if (unlikely(ret)) {
loff_t isize = i_size_read(mapping->host);
if (ret != AOP_TRUNCATED_PAGE)
unlock_page(page);
page_cache_release(page);
if (ret == AOP_TRUNCATED_PAGE)
goto find_page;
/*
* prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again.
*/
if (sd->pos + this_len > isize)
vmtruncate(mapping->host, isize);
goto out;
}
if (buf->page != page) {
/*
* Careful, ->map() uses KM_USER0!
*/
char *src = buf->ops->map(pipe, buf, 1);
char *dst = kmap_atomic(page, KM_USER1);
memcpy(dst + offset, src + buf->offset, this_len);
flush_dcache_page(page);
kunmap_atomic(dst, KM_USER1);
buf->ops->unmap(pipe, buf, src);
}
ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
if (!ret) {
/*
* Return the number of bytes written and mark page as
* accessed, we are now done!
*/
ret = this_len;
mark_page_accessed(page);
balance_dirty_pages_ratelimited(mapping);
} else if (ret == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto find_page;
}
out:
page_cache_release(page);
unlock_page(page);
out_nomem:
return ret;
}
/*
* Pipe input worker. Most of this logic works like a regular pipe, the
* key here is the 'actor' worker passed in that actually moves the data
* to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
*/
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)
{
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 = *ppos;
if (pipe->inode)
mutex_lock(&pipe->inode->i_mutex);
for (;;) {
if (pipe->nrbufs) {
struct pipe_buffer *buf = pipe->bufs + pipe->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(pipe, buf, &sd);
if (err <= 0) {
if (!ret && err != -ENODATA)
ret = err;
break;
}
ret += err;
buf->offset += err;
buf->len -= err;
sd.len -= err;
sd.pos += err;
sd.total_len -= err;
if (sd.len)
continue;
if (!buf->len) {
buf->ops = NULL;
ops->release(pipe, buf);
pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
pipe->nrbufs--;
if (pipe->inode)
do_wakeup = 1;
}
if (!sd.total_len)
break;
}
if (pipe->nrbufs)
continue;
if (!pipe->writers)
break;
if (!pipe->waiting_writers) {
if (ret)
break;
}
if (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_writers, SIGIO, POLL_OUT);
do_wakeup = 0;
}
pipe_wait(pipe);
}
if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);
if (do_wakeup) {
smp_mb();
if (waitqueue_active(&pipe->wait))
wake_up_interruptible(&pipe->wait);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}
return ret;
}
/**
* generic_file_splice_write - splice data from a pipe to a file
* @pipe: pipe info
* @out: file to write to
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* 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;
ssize_t ret;
ret = splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
if (ret > 0) {
struct inode *inode = mapping->host;
*ppos += ret;
/*
* If file or inode is SYNC and we actually wrote some data,
* sync it.
*/
if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
int err;
mutex_lock(&inode->i_mutex);
err = generic_osync_inode(inode, mapping,
OSYNC_METADATA|OSYNC_DATA);
mutex_unlock(&inode->i_mutex);
if (err)
ret = err;
}
}
return ret;
}
EXPORT_SYMBOL(generic_file_splice_write);
/**
* generic_splice_sendpage - splice data from a pipe to a socket
* @inode: pipe inode
* @out: socket to write to
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* 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)
{
int ret;
if (unlikely(!out->f_op || !out->f_op->splice_write))
return -EINVAL;
if (unlikely(!(out->f_mode & FMODE_WRITE)))
return -EBADF;
ret = rw_verify_area(WRITE, out, ppos, len);
if (unlikely(ret < 0))
return ret;
return out->f_op->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)
{
loff_t isize, left;
int ret;
if (unlikely(!in->f_op || !in->f_op->splice_read))
return -EINVAL;
if (unlikely(!(in->f_mode & FMODE_READ)))
return -EBADF;
ret = rw_verify_area(READ, in, ppos, len);
if (unlikely(ret < 0))
return ret;
isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
return 0;
left = isize - *ppos;
if (unlikely(left < len))
len = left;
return in->f_op->splice_read(in, ppos, pipe, len, flags);
}
long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
size_t len, unsigned int flags)
{
struct pipe_inode_info *pipe;
long ret, bytes;
loff_t out_off;
umode_t i_mode;
int i;
/*
* 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_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;
out_off = 0;
while (len) {
size_t read_len, max_read_len;
/*
* Do at most PIPE_BUFFERS pages worth of transfer:
*/
max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
if (unlikely(ret < 0))
goto out_release;
read_len = ret;
/*
* 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 = do_splice_from(pipe, out, &out_off, read_len,
flags & ~SPLICE_F_NONBLOCK);
if (unlikely(ret < 0))
goto out_release;
bytes += ret;
len -= ret;
/*
* In nonblocking mode, if we got back a short read then
* that was due to either an IO error or due to the
* pagecache entry not being there. In the IO error case
* the _next_ splice attempt will produce a clean IO error
* return value (not a short read), so in both cases it's
* correct to break out of the loop here:
*/
if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))
break;
}
pipe->nrbufs = pipe->curbuf = 0;
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;
}
}
pipe->nrbufs = pipe->curbuf = 0;
/*
* If we transferred some data, return the number of bytes:
*/
if (bytes > 0)
return bytes;
return ret;
}
EXPORT_SYMBOL(do_splice_direct);
/*
* 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 *pipe;
loff_t offset, *off;
long ret;
pipe = in->f_dentry->d_inode->i_pipe;
if (pipe) {
if (off_in)
return -ESPIPE;
if (off_out) {
if (out->f_op->llseek == no_llseek)
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(pipe, out, off, len, flags);
if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
ret = -EFAULT;
return ret;
}
pipe = out->f_dentry->d_inode->i_pipe;
if (pipe) {
if (off_out)
return -ESPIPE;
if (off_in) {
if (in->f_op->llseek == no_llseek)
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, pipe, 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, int aligned)
{
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;
/*
* 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(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,
flags & SPLICE_F_GIFT);
if (spd.nr_pages <= 0)
return spd.nr_pages;
return splice_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)
{
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;
}
/*
* 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, do_wakeup, i, ipipe_first;
ret = do_wakeup = ipipe_first = 0;
/*
* Potential ABBA deadlock, work around it by ordering lock
* grabbing by inode address. Otherwise two different processes
* could deadlock (one doing tee from A -> B, the other from B -> A).
*/
if (ipipe->inode < opipe->inode) {
ipipe_first = 1;
mutex_lock(&ipipe->inode->i_mutex);
mutex_lock(&opipe->inode->i_mutex);
} else {
mutex_lock(&opipe->inode->i_mutex);
mutex_lock(&ipipe->inode->i_mutex);
}
for (i = 0;; i++) {
if (!opipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
if (ipipe->nrbufs - i) {
ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
/*
* If we have room, fill this buffer
*/
if (opipe->nrbufs < PIPE_BUFFERS) {
int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_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++;
do_wakeup = 1;
ret += obuf->len;
len -= obuf->len;
if (!len)
break;
if (opipe->nrbufs < PIPE_BUFFERS)
continue;
}
/*
* We have input available, but no output room.
* If we already copied data, return that. If we
* need to drop the opipe lock, it must be ordered
* last to avoid deadlocks.
*/
if ((flags & SPLICE_F_NONBLOCK) || !ipipe_first) {
if (!ret)
ret = -EAGAIN;
break;
}
if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}
if (do_wakeup) {
smp_mb();
if (waitqueue_active(&opipe->wait))
wake_up_interruptible(&opipe->wait);
kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
do_wakeup = 0;
}
opipe->waiting_writers++;
pipe_wait(opipe);
opipe->waiting_writers--;
continue;
}
/*
* No input buffers, do the usual checks for available
* writers and blocking and wait if necessary
*/
if (!ipipe->writers)
break;
if (!ipipe->waiting_writers) {
if (ret)
break;
}
/*
* pipe_wait() drops the ipipe mutex. To avoid deadlocks
* with another process, we can only safely do that if
* the ipipe lock is ordered last.
*/
if ((flags & SPLICE_F_NONBLOCK) || ipipe_first) {
if (!ret)
ret = -EAGAIN;
break;
}
if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}
if (waitqueue_active(&ipipe->wait))
wake_up_interruptible_sync(&ipipe->wait);
kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT);
pipe_wait(ipipe);
}
mutex_unlock(&ipipe->inode->i_mutex);
mutex_unlock(&opipe->inode->i_mutex);
if (do_wakeup) {
smp_mb();
if (waitqueue_active(&opipe->wait))
wake_up_interruptible(&opipe->wait);
kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
}
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 = in->f_dentry->d_inode->i_pipe;
struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
/*
* Link ipipe to the two output pipes, consuming as we go along.
*/
if (ipipe && opipe)
return link_pipe(ipipe, opipe, len, flags);
return -EINVAL;
}
asmlinkage long sys_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;
}