Revision 9e0af23764344f7f1b68e4eefbe7dc865018b63d authored by Liu Bo on 15 August 2014, 15:36:53 UTC, committed by Chris Mason on 24 August 2014, 14:17:02 UTC
This has been reported and discussed for a long time, and this hang occurs in both 3.15 and 3.16. Btrfs now migrates to use kernel workqueue, but it introduces this hang problem. Btrfs has a kind of work queued as an ordered way, which means that its ordered_func() must be processed in the way of FIFO, so it usually looks like -- normal_work_helper(arg) work = container_of(arg, struct btrfs_work, normal_work); work->func() <---- (we name it work X) for ordered_work in wq->ordered_list ordered_work->ordered_func() ordered_work->ordered_free() The hang is a rare case, first when we find free space, we get an uncached block group, then we go to read its free space cache inode for free space information, so it will file a readahead request btrfs_readpages() for page that is not in page cache __do_readpage() submit_extent_page() btrfs_submit_bio_hook() btrfs_bio_wq_end_io() submit_bio() end_workqueue_bio() <--(ret by the 1st endio) queue a work(named work Y) for the 2nd also the real endio() So the hang occurs when work Y's work_struct and work X's work_struct happens to share the same address. A bit more explanation, A,B,C -- struct btrfs_work arg -- struct work_struct kthread: worker_thread() pick up a work_struct from @worklist process_one_work(arg) worker->current_work = arg; <-- arg is A->normal_work worker->current_func(arg) normal_work_helper(arg) A = container_of(arg, struct btrfs_work, normal_work); A->func() A->ordered_func() A->ordered_free() <-- A gets freed B->ordered_func() submit_compressed_extents() find_free_extent() load_free_space_inode() ... <-- (the above readhead stack) end_workqueue_bio() btrfs_queue_work(work C) B->ordered_free() As if work A has a high priority in wq->ordered_list and there are more ordered works queued after it, such as B->ordered_func(), its memory could have been freed before normal_work_helper() returns, which means that kernel workqueue code worker_thread() still has worker->current_work pointer to be work A->normal_work's, ie. arg's address. Meanwhile, work C is allocated after work A is freed, work C->normal_work and work A->normal_work are likely to share the same address(I confirmed this with ftrace output, so I'm not just guessing, it's rare though). When another kthread picks up work C->normal_work to process, and finds our kthread is processing it(see find_worker_executing_work()), it'll think work C as a collision and skip then, which ends up nobody processing work C. So the situation is that our kthread is waiting forever on work C. Besides, there're other cases that can lead to deadlock, but the real problem is that all btrfs workqueue shares one work->func, -- normal_work_helper, so this makes each workqueue to have its own helper function, but only a wraper pf normal_work_helper. With this patch, I no long hit the above hang. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Chris Mason <clm@fb.com>
1 parent f6dc45c
splice.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@kernel.dk>
* Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
* Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
*
*/
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/memcontrol.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/uio.h>
#include <linux/security.h>
#include <linux/gfp.h>
#include <linux/socket.h>
#include <linux/compat.h>
#include <linux/aio.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)
{
page_cache_release(buf->page);
buf->flags &= ~PIPE_BUF_FLAG_LRU;
}
/*
* Check whether the contents of buf is OK to access. Since the content
* is a page cache page, IO may be in flight.
*/
static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
struct page *page = buf->page;
int err;
if (!PageUptodate(page)) {
lock_page(page);
/*
* Page got truncated/unhashed. This will cause a 0-byte
* splice, if this is the first page.
*/
if (!page->mapping) {
err = -ENODATA;
goto error;
}
/*
* Uh oh, read-error from disk.
*/
if (!PageUptodate(page)) {
err = -EIO;
goto error;
}
/*
* Page is ok afterall, we are done.
*/
unlock_page(page);
}
return 0;
error:
unlock_page(page);
return err;
}
const struct pipe_buf_operations page_cache_pipe_buf_ops = {
.can_merge = 0,
.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, do_wakeup, page_nr;
ret = 0;
do_wakeup = 0;
page_nr = 0;
pipe_lock(pipe);
for (;;) {
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
if (pipe->nrbufs < pipe->buffers) {
int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
struct pipe_buffer *buf = pipe->bufs + newbuf;
buf->page = spd->pages[page_nr];
buf->offset = spd->partial[page_nr].offset;
buf->len = spd->partial[page_nr].len;
buf->private = spd->partial[page_nr].private;
buf->ops = spd->ops;
if (spd->flags & SPLICE_F_GIFT)
buf->flags |= PIPE_BUF_FLAG_GIFT;
pipe->nrbufs++;
page_nr++;
ret += buf->len;
if (pipe->files)
do_wakeup = 1;
if (!--spd->nr_pages)
break;
if (pipe->nrbufs < pipe->buffers)
continue;
break;
}
if (spd->flags & SPLICE_F_NONBLOCK) {
if (!ret)
ret = -EAGAIN;
break;
}
if (signal_pending(current)) {
if (!ret)
ret = -ERESTARTSYS;
break;
}
if (do_wakeup) {
smp_mb();
if (waitqueue_active(&pipe->wait))
wake_up_interruptible_sync(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
do_wakeup = 0;
}
pipe->waiting_writers++;
pipe_wait(pipe);
pipe->waiting_writers--;
}
pipe_unlock(pipe);
if (do_wakeup)
wakeup_pipe_readers(pipe);
while (page_nr < spd_pages)
spd->spd_release(spd, page_nr++);
return ret;
}
void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
{
page_cache_release(spd->pages[i]);
}
/*
* Check if we need to grow the arrays holding pages and partial page
* descriptions.
*/
int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
{
unsigned int buffers = ACCESS_ONCE(pipe->buffers);
spd->nr_pages_max = buffers;
if (buffers <= PIPE_DEF_BUFFERS)
return 0;
spd->pages = kmalloc(buffers * sizeof(struct page *), GFP_KERNEL);
spd->partial = kmalloc(buffers * sizeof(struct partial_page), GFP_KERNEL);
if (spd->pages && spd->partial)
return 0;
kfree(spd->pages);
kfree(spd->partial);
return -ENOMEM;
}
void splice_shrink_spd(struct splice_pipe_desc *spd)
{
if (spd->nr_pages_max <= PIPE_DEF_BUFFERS)
return;
kfree(spd->pages);
kfree(spd->partial);
}
static int
__generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct address_space *mapping = in->f_mapping;
unsigned int loff, nr_pages, req_pages;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct page *page;
pgoff_t index, end_index;
loff_t isize;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &page_cache_pipe_buf_ops,
.spd_release = spd_release_page,
};
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
index = *ppos >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
nr_pages = min(req_pages, spd.nr_pages_max);
/*
* Lookup the (hopefully) full range of pages we need.
*/
spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
index += spd.nr_pages;
/*
* If find_get_pages_contig() returned fewer pages than we needed,
* readahead/allocate the rest and fill in the holes.
*/
if (spd.nr_pages < nr_pages)
page_cache_sync_readahead(mapping, &in->f_ra, in,
index, req_pages - spd.nr_pages);
error = 0;
while (spd.nr_pages < nr_pages) {
/*
* Page could be there, find_get_pages_contig() breaks on
* the first hole.
*/
page = find_get_page(mapping, index);
if (!page) {
/*
* page didn't exist, allocate one.
*/
page = page_cache_alloc_cold(mapping);
if (!page)
break;
error = add_to_page_cache_lru(page, mapping, index,
GFP_KERNEL);
if (unlikely(error)) {
page_cache_release(page);
if (error == -EEXIST)
continue;
break;
}
/*
* add_to_page_cache() locks the page, unlock it
* to avoid convoluting the logic below even more.
*/
unlock_page(page);
}
spd.pages[spd.nr_pages++] = page;
index++;
}
/*
* Now loop over the map and see if we need to start IO on any
* pages, fill in the partial map, etc.
*/
index = *ppos >> PAGE_CACHE_SHIFT;
nr_pages = spd.nr_pages;
spd.nr_pages = 0;
for (page_nr = 0; page_nr < nr_pages; page_nr++) {
unsigned int this_len;
if (!len)
break;
/*
* this_len is the max we'll use from this page
*/
this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
page = spd.pages[page_nr];
if (PageReadahead(page))
page_cache_async_readahead(mapping, &in->f_ra, in,
page, index, req_pages - page_nr);
/*
* If the page isn't uptodate, we may need to start io on it
*/
if (!PageUptodate(page)) {
lock_page(page);
/*
* Page was truncated, or invalidated by the
* filesystem. Redo the find/create, but this time the
* page is kept locked, so there's no chance of another
* race with truncate/invalidate.
*/
if (!page->mapping) {
unlock_page(page);
page = find_or_create_page(mapping, index,
mapping_gfp_mask(mapping));
if (!page) {
error = -ENOMEM;
break;
}
page_cache_release(spd.pages[page_nr]);
spd.pages[page_nr] = page;
}
/*
* page was already under io and is now done, great
*/
if (PageUptodate(page)) {
unlock_page(page);
goto fill_it;
}
/*
* need to read in the page
*/
error = mapping->a_ops->readpage(in, page);
if (unlikely(error)) {
/*
* We really should re-lookup the page here,
* but it complicates things a lot. Instead
* lets just do what we already stored, and
* we'll get it the next time we are called.
*/
if (error == AOP_TRUNCATED_PAGE)
error = 0;
break;
}
}
fill_it:
/*
* i_size must be checked after PageUptodate.
*/
isize = i_size_read(mapping->host);
end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
if (unlikely(!isize || index > end_index))
break;
/*
* if this is the last page, see if we need to shrink
* the length and stop
*/
if (end_index == index) {
unsigned int plen;
/*
* max good bytes in this page
*/
plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
if (plen <= loff)
break;
/*
* force quit after adding this page
*/
this_len = min(this_len, plen - loff);
len = this_len;
}
spd.partial[page_nr].offset = loff;
spd.partial[page_nr].len = this_len;
len -= this_len;
loff = 0;
spd.nr_pages++;
index++;
}
/*
* Release any pages at the end, if we quit early. 'page_nr' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)
page_cache_release(spd.pages[page_nr++]);
in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
if (spd.nr_pages)
error = splice_to_pipe(pipe, &spd);
splice_shrink_spd(&spd);
return error;
}
/**
* generic_file_splice_read - splice data from file to a pipe
* @in: file to splice from
* @ppos: position in @in
* @pipe: pipe to splice to
* @len: number of bytes to splice
* @flags: splice modifier flags
*
* Description:
* Will read pages from given file and fill them into a pipe. Can be
* used as long as the address_space operations for the source implements
* a readpage() hook.
*
*/
ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
loff_t isize, left;
int ret;
isize = i_size_read(in->f_mapping->host);
if (unlikely(*ppos >= isize))
return 0;
left = isize - *ppos;
if (unlikely(left < len))
len = left;
ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
if (ret > 0) {
*ppos += ret;
file_accessed(in);
}
return ret;
}
EXPORT_SYMBOL(generic_file_splice_read);
static const struct pipe_buf_operations default_pipe_buf_ops = {
.can_merge = 0,
.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 iovec *vec,
unsigned long vlen, loff_t offset)
{
mm_segment_t old_fs;
loff_t pos = offset;
ssize_t res;
old_fs = get_fs();
set_fs(get_ds());
/* The cast to a user pointer is valid due to the set_fs() */
res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
set_fs(old_fs);
return res;
}
ssize_t kernel_write(struct file *file, const char *buf, size_t count,
loff_t pos)
{
mm_segment_t old_fs;
ssize_t res;
old_fs = get_fs();
set_fs(get_ds());
/* The cast to a user pointer is valid due to the set_fs() */
res = vfs_write(file, (__force const char __user *)buf, count, &pos);
set_fs(old_fs);
return res;
}
EXPORT_SYMBOL(kernel_write);
ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
unsigned int nr_pages;
unsigned int nr_freed;
size_t offset;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
ssize_t res;
size_t this_len;
int error;
int i;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &default_pipe_buf_ops,
.spd_release = spd_release_page,
};
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
res = -ENOMEM;
vec = __vec;
if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
if (!vec)
goto shrink_ret;
}
offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
struct page *page;
page = alloc_page(GFP_USER);
error = -ENOMEM;
if (!page)
goto err;
this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
vec[i].iov_base = (void __user *) page_address(page);
vec[i].iov_len = this_len;
spd.pages[i] = page;
spd.nr_pages++;
len -= this_len;
offset = 0;
}
res = kernel_readv(in, vec, spd.nr_pages, *ppos);
if (res < 0) {
error = res;
goto err;
}
error = 0;
if (!res)
goto err;
nr_freed = 0;
for (i = 0; i < spd.nr_pages; i++) {
this_len = min_t(size_t, vec[i].iov_len, res);
spd.partial[i].offset = 0;
spd.partial[i].len = this_len;
if (!this_len) {
__free_page(spd.pages[i]);
spd.pages[i] = NULL;
nr_freed++;
}
res -= this_len;
}
spd.nr_pages -= nr_freed;
res = splice_to_pipe(pipe, &spd);
if (res > 0)
*ppos += res;
shrink_ret:
if (vec != __vec)
kfree(vec);
splice_shrink_spd(&spd);
return res;
err:
for (i = 0; i < spd.nr_pages; i++)
__free_page(spd.pages[i]);
res = error;
goto shrink_ret;
}
EXPORT_SYMBOL(default_file_splice_read);
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
*/
static int pipe_to_sendpage(struct pipe_inode_info *pipe,
struct pipe_buffer *buf, struct splice_desc *sd)
{
struct file *file = sd->u.file;
loff_t pos = sd->pos;
int more;
if (!likely(file->f_op->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;
const struct pipe_buf_operations *ops = buf->ops;
sd->len = buf->len;
if (sd->len > sd->total_len)
sd->len = sd->total_len;
ret = buf->ops->confirm(pipe, buf);
if (unlikely(ret)) {
if (ret == -ENODATA)
ret = 0;
return ret;
}
ret = actor(pipe, buf, sd);
if (ret <= 0)
return ret;
buf->offset += ret;
buf->len -= ret;
sd->num_spliced += ret;
sd->len -= ret;
sd->pos += ret;
sd->total_len -= ret;
if (!buf->len) {
buf->ops = NULL;
ops->release(pipe, buf);
pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
pipe->nrbufs--;
if (pipe->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)
{
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 {
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;
struct kiocb kiocb;
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 = buf->ops->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 */
from.type = ITER_BVEC | WRITE;
from.bvec = array;
from.nr_segs = n;
from.count = sd.total_len - left;
from.iov_offset = 0;
/* ... and iocb */
init_sync_kiocb(&kiocb, out);
kiocb.ki_pos = sd.pos;
kiocb.ki_nbytes = sd.total_len - left;
/* now, send it */
ret = out->f_op->write_iter(&kiocb, &from);
if (-EIOCBQUEUED == ret)
ret = wait_on_sync_kiocb(&kiocb);
if (ret <= 0)
break;
sd.num_spliced += ret;
sd.total_len -= ret;
*ppos = sd.pos = kiocb.ki_pos;
/* dismiss the fully eaten buffers, adjust the partial one */
while (ret) {
struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
if (ret >= buf->len) {
const struct pipe_buf_operations *ops = buf->ops;
ret -= buf->len;
buf->len = 0;
buf->ops = NULL;
ops->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 (in->f_op->splice_read)
splice_read = in->f_op->splice_read;
else
splice_read = default_file_splice_read;
return splice_read(in, ppos, pipe, len, flags);
}
/**
* splice_direct_to_actor - splices data directly between two non-pipes
* @in: file to splice from
* @sd: actor information on where to splice to
* @actor: handles the data splicing
*
* Description:
* This is a special case helper to splice directly between two
* points, without requiring an explicit pipe. Internally an allocated
* pipe is cached in the process, and reused during the lifetime of
* that process.
*
*/
ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
splice_direct_actor *actor)
{
struct pipe_inode_info *pipe;
long ret, bytes;
umode_t i_mode;
size_t len;
int i, flags;
/*
* We require the input being a regular file, as we don't want to
* randomly drop data for eg socket -> socket splicing. Use the
* piped splicing for that!
*/
i_mode = 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;
while (len) {
size_t read_len;
loff_t pos = sd->pos, prev_pos = pos;
ret = do_splice_to(in, &pos, pipe, len, flags);
if (unlikely(ret <= 0))
goto out_release;
read_len = ret;
sd->total_len = read_len;
/*
* NOTE: nonblocking mode only applies to the input. We
* must not do the output in nonblocking mode as then we
* could get stuck data in the internal pipe:
*/
ret = actor(pipe, sd);
if (unlikely(ret <= 0)) {
sd->pos = prev_pos;
goto out_release;
}
bytes += ret;
len -= ret;
sd->pos = pos;
if (ret < read_len) {
sd->pos = prev_pos + ret;
goto out_release;
}
}
done:
pipe->nrbufs = pipe->curbuf = 0;
file_accessed(in);
return bytes;
out_release:
/*
* If we did an incomplete transfer we must release
* the pipe buffers in question:
*/
for (i = 0; i < pipe->buffers; i++) {
struct pipe_buffer *buf = pipe->bufs + i;
if (buf->ops) {
buf->ops->release(pipe, buf);
buf->ops = NULL;
}
}
if (!bytes)
bytes = ret;
goto done;
}
EXPORT_SYMBOL(splice_direct_to_actor);
static int direct_splice_actor(struct pipe_inode_info *pipe,
struct splice_desc *sd)
{
struct file *file = sd->u.file;
return do_splice_from(pipe, file, 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;
}
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;
}
ret = do_splice_to(in, &offset, opipe, len, flags);
if (!off_in)
in->f_pos = offset;
else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
ret = -EFAULT;
return ret;
}
return -EINVAL;
}
/*
* Map an iov into an array of pages and offset/length tupples. With the
* partial_page structure, we can map several non-contiguous ranges into
* our ones pages[] map instead of splitting that operation into pieces.
* Could easily be exported as a generic helper for other users, in which
* case one would probably want to add a 'max_nr_pages' parameter as well.
*/
static int get_iovec_page_array(const struct iovec __user *iov,
unsigned int nr_vecs, struct page **pages,
struct partial_page *partial, bool aligned,
unsigned int pipe_buffers)
{
int buffers = 0, error = 0;
while (nr_vecs) {
unsigned long off, npages;
struct iovec entry;
void __user *base;
size_t len;
int i;
error = -EFAULT;
if (copy_from_user(&entry, iov, sizeof(entry)))
break;
base = entry.iov_base;
len = entry.iov_len;
/*
* Sanity check this iovec. 0 read succeeds.
*/
error = 0;
if (unlikely(!len))
break;
error = -EFAULT;
if (!access_ok(VERIFY_READ, base, len))
break;
/*
* Get this base offset and number of pages, then map
* in the user pages.
*/
off = (unsigned long) base & ~PAGE_MASK;
/*
* If asked for alignment, the offset must be zero and the
* length a multiple of the PAGE_SIZE.
*/
error = -EINVAL;
if (aligned && (off || len & ~PAGE_MASK))
break;
npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (npages > pipe_buffers - buffers)
npages = pipe_buffers - buffers;
error = get_user_pages_fast((unsigned long)base, npages,
0, &pages[buffers]);
if (unlikely(error <= 0))
break;
/*
* Fill this contiguous range into the partial page map.
*/
for (i = 0; i < error; i++) {
const int plen = min_t(size_t, len, PAGE_SIZE - off);
partial[buffers].offset = off;
partial[buffers].len = plen;
off = 0;
len -= plen;
buffers++;
}
/*
* We didn't complete this iov, stop here since it probably
* means we have to move some of this into a pipe to
* be able to continue.
*/
if (len)
break;
/*
* Don't continue if we mapped fewer pages than we asked for,
* or if we mapped the max number of pages that we have
* room for.
*/
if (error < npages || buffers == pipe_buffers)
break;
nr_vecs--;
iov++;
}
if (buffers)
return buffers;
return error;
}
static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
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, const struct iovec __user *uiov,
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe;
struct splice_desc sd;
long ret;
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
struct iov_iter iter;
ssize_t count;
pipe = get_pipe_info(file);
if (!pipe)
return -EBADF;
ret = rw_copy_check_uvector(READ, uiov, nr_segs,
ARRAY_SIZE(iovstack), iovstack, &iov);
if (ret <= 0)
goto out;
count = ret;
iov_iter_init(&iter, READ, iov, nr_segs, count);
sd.len = 0;
sd.total_len = count;
sd.flags = flags;
sd.u.data = &iter;
sd.pos = 0;
pipe_lock(pipe);
ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
pipe_unlock(pipe);
out:
if (iov != iovstack)
kfree(iov);
return ret;
}
/*
* vmsplice splices a user address range into a pipe. It can be thought of
* as splice-from-memory, where the regular splice is splice-from-file (or
* to file). In both cases the output is a pipe, naturally.
*/
static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
unsigned long nr_segs, unsigned int flags)
{
struct pipe_inode_info *pipe;
struct page *pages[PIPE_DEF_BUFFERS];
struct partial_page partial[PIPE_DEF_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.nr_pages_max = PIPE_DEF_BUFFERS,
.flags = flags,
.ops = &user_page_pipe_buf_ops,
.spd_release = spd_release_page,
};
long ret;
pipe = get_pipe_info(file);
if (!pipe)
return -EBADF;
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
spd.partial, false,
spd.nr_pages_max);
if (spd.nr_pages <= 0)
ret = spd.nr_pages;
else
ret = splice_to_pipe(pipe, &spd);
splice_shrink_spd(&spd);
return ret;
}
/*
* Note that vmsplice only really supports true splicing _from_ user memory
* to a pipe, not the other way around. Splicing from user memory is a simple
* operation that can be supported without any funky alignment restrictions
* or nasty vm tricks. We simply map in the user memory and fill them into
* a pipe. The reverse isn't quite as easy, though. There are two possible
* solutions for that:
*
* - memcpy() the data internally, at which point we might as well just
* do a regular read() on the buffer anyway.
* - Lots of nasty vm tricks, that are neither fast nor flexible (it
* has restriction limitations on both ends of the pipe).
*
* Currently we punt and implement it as a normal copy, see pipe_to_user().
*
*/
SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
unsigned long, nr_segs, unsigned int, flags)
{
struct fd f;
long error;
if (unlikely(nr_segs > UIO_MAXIOV))
return -EINVAL;
else if (unlikely(!nr_segs))
return 0;
error = -EBADF;
f = fdget(fd);
if (f.file) {
if (f.file->f_mode & FMODE_WRITE)
error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
else if (f.file->f_mode & FMODE_READ)
error = vmsplice_to_user(f.file, iov, nr_segs, flags);
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)
{
unsigned i;
struct iovec __user *iov;
if (nr_segs > UIO_MAXIOV)
return -EINVAL;
iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
for (i = 0; i < nr_segs; i++) {
struct compat_iovec v;
if (get_user(v.iov_base, &iov32[i].iov_base) ||
get_user(v.iov_len, &iov32[i].iov_len) ||
put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
put_user(v.iov_len, &iov[i].iov_len))
return -EFAULT;
}
return sys_vmsplice(fd, iov, nr_segs, flags);
}
#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;
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.
*/
ibuf->ops->get(ipipe, ibuf);
*obuf = *ibuf;
/*
* Don't inherit the gift flag, we need to
* prevent multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
obuf->len = len;
opipe->nrbufs++;
ibuf->offset += obuf->len;
ibuf->len -= obuf->len;
}
ret += obuf->len;
len -= obuf->len;
} while (len);
pipe_unlock(ipipe);
pipe_unlock(opipe);
/*
* If we put data in the output pipe, wakeup any potential readers.
*/
if (ret > 0)
wakeup_pipe_readers(opipe);
if (input_wakeup)
wakeup_pipe_writers(ipipe);
return ret;
}
/*
* Link contents of ipipe to opipe.
*/
static int link_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags)
{
struct pipe_buffer *ibuf, *obuf;
int ret = 0, i = 0, nbuf;
/*
* Potential ABBA deadlock, work around it by ordering lock
* grabbing by pipe info address. Otherwise two different processes
* could deadlock (one doing tee from A -> B, the other from B -> A).
*/
pipe_double_lock(ipipe, opipe);
do {
if (!opipe->readers) {
send_sig(SIGPIPE, current, 0);
if (!ret)
ret = -EPIPE;
break;
}
/*
* If we have iterated all input buffers or ran out of
* output room, break.
*/
if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
break;
ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
/*
* Get a reference to this pipe buffer,
* so we can copy the contents over.
*/
ibuf->ops->get(ipipe, ibuf);
obuf = opipe->bufs + nbuf;
*obuf = *ibuf;
/*
* Don't inherit the gift flag, we need to
* prevent multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
if (obuf->len > len)
obuf->len = len;
opipe->nrbufs++;
ret += obuf->len;
len -= obuf->len;
i++;
} while (len);
/*
* return EAGAIN if we have the potential of some data in the
* future, otherwise just return 0
*/
if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
ret = -EAGAIN;
pipe_unlock(ipipe);
pipe_unlock(opipe);
/*
* If we put data in the output pipe, wakeup any potential readers.
*/
if (ret > 0)
wakeup_pipe_readers(opipe);
return ret;
}
/*
* This is a tee(1) implementation that works on pipes. It doesn't copy
* any data, it simply references the 'in' pages on the 'out' pipe.
* The 'flags' used are the SPLICE_F_* variants, currently the only
* applicable one is SPLICE_F_NONBLOCK.
*/
static long do_tee(struct file *in, struct file *out, size_t len,
unsigned int flags)
{
struct pipe_inode_info *ipipe = get_pipe_info(in);
struct pipe_inode_info *opipe = get_pipe_info(out);
int ret = -EINVAL;
/*
* Duplicate the contents of ipipe to opipe without actually
* copying the data.
*/
if (ipipe && opipe && ipipe != opipe) {
/*
* Keep going, unless we encounter an error. The ipipe/opipe
* ordering doesn't really matter.
*/
ret = ipipe_prep(ipipe, flags);
if (!ret) {
ret = opipe_prep(opipe, flags);
if (!ret)
ret = link_pipe(ipipe, opipe, len, flags);
}
}
return ret;
}
SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
{
struct fd in;
int error;
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;
}
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