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Commit c3021629 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: support splice() reading from fuse device 



Allow userspace filesystem implementation to use splice() to read from
the fuse device.

The userspace filesystem can now transfer data coming from a WRITE
request to an arbitrary file descriptor (regular file, block device or
socket) without having to go through a userspace buffer.

The semantics of using splice() to read messages are:

 1)  with a single splice() call move the whole message from the fuse
     device to a temporary pipe
 2)  read the header from the pipe and determine the message type
 3a) if message is a WRITE then splice data from pipe to destination
 3b) else read rest of message to userspace buffer

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent ce534fb0

fs/fuse/dev.c

+187 −41
Original line number Diff line number Diff line
@@ -515,13 +515,12 @@ struct fuse_copy_state { 
};



static void fuse_copy_init(struct fuse_copy_state *cs, struct fuse_conn *fc,

			   int write, struct fuse_req *req,

			   int write,

			   const struct iovec *iov, unsigned long nr_segs)

{

	memset(cs, 0, sizeof(*cs));

	cs->fc = fc;

	cs->write = write;

	cs->req = req;

	cs->iov = iov;

	cs->nr_segs = nr_segs;

}
@@ -532,8 +531,12 @@ static void fuse_copy_finish(struct fuse_copy_state *cs) 
	if (cs->currbuf) {

		struct pipe_buffer *buf = cs->currbuf;



		if (!cs->write) {

			buf->ops->unmap(cs->pipe, buf, cs->mapaddr);



		} else {

			kunmap_atomic(cs->mapaddr, KM_USER0);

			buf->len = PAGE_SIZE - cs->len;

		}

		cs->currbuf = NULL;

		cs->mapaddr = NULL;

	} else if (cs->mapaddr) {
@@ -561,6 +564,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs) 
	if (cs->pipebufs) {

		struct pipe_buffer *buf = cs->pipebufs;



		if (!cs->write) {

			err = buf->ops->confirm(cs->pipe, buf);

			if (err)

				return err;
@@ -572,6 +576,27 @@ static int fuse_copy_fill(struct fuse_copy_state *cs) 
			cs->buf = cs->mapaddr + buf->offset;

			cs->pipebufs++;

			cs->nr_segs--;

		} else {

			struct page *page;



			if (cs->nr_segs == cs->pipe->buffers)

				return -EIO;



			page = alloc_page(GFP_HIGHUSER);

			if (!page)

				return -ENOMEM;



			buf->page = page;

			buf->offset = 0;

			buf->len = 0;



			cs->currbuf = buf;

			cs->mapaddr = kmap_atomic(page, KM_USER0);

			cs->buf = cs->mapaddr;

			cs->len = PAGE_SIZE;

			cs->pipebufs++;

			cs->nr_segs++;

		}

	} else {

		if (!cs->seglen) {

			BUG_ON(!cs->nr_segs);
@@ -731,6 +756,30 @@ out_fallback: 
	return 1;

}



static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,

			 unsigned offset, unsigned count)

{

	struct pipe_buffer *buf;



	if (cs->nr_segs == cs->pipe->buffers)

		return -EIO;



	unlock_request(cs->fc, cs->req);

	fuse_copy_finish(cs);



	buf = cs->pipebufs;

	page_cache_get(page);

	buf->page = page;

	buf->offset = offset;

	buf->len = count;



	cs->pipebufs++;

	cs->nr_segs++;

	cs->len = 0;



	return 0;

}



/*

 * Copy a page in the request to/from the userspace buffer.  Must be

 * done atomically
@@ -747,7 +796,9 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep, 
		kunmap_atomic(mapaddr, KM_USER1);

	}

	while (count) {

		if (!cs->len) {

		if (cs->write && cs->pipebufs && page) {

			return fuse_ref_page(cs, page, offset, count);

		} else if (!cs->len) {

			if (cs->move_pages && page &&

			    offset == 0 && count == PAGE_SIZE) {

				err = fuse_try_move_page(cs, pagep);
@@ -862,11 +913,10 @@ __acquires(&fc->lock) 
 *

 * Called with fc->lock held, releases it

 */

static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_req *req,

			       const struct iovec *iov, unsigned long nr_segs)

static int fuse_read_interrupt(struct fuse_conn *fc, struct fuse_copy_state *cs,

			       size_t nbytes, struct fuse_req *req)

__releases(&fc->lock)

{

	struct fuse_copy_state cs;

	struct fuse_in_header ih;

	struct fuse_interrupt_in arg;

	unsigned reqsize = sizeof(ih) + sizeof(arg);
@@ -882,14 +932,13 @@ __releases(&fc->lock) 
	arg.unique = req->in.h.unique;



	spin_unlock(&fc->lock);

	if (iov_length(iov, nr_segs) < reqsize)

	if (nbytes < reqsize)

		return -EINVAL;



	fuse_copy_init(&cs, fc, 1, NULL, iov, nr_segs);

	err = fuse_copy_one(&cs, &ih, sizeof(ih));

	err = fuse_copy_one(cs, &ih, sizeof(ih));

	if (!err)

		err = fuse_copy_one(&cs, &arg, sizeof(arg));

	fuse_copy_finish(&cs);

		err = fuse_copy_one(cs, &arg, sizeof(arg));

	fuse_copy_finish(cs);



	return err ? err : reqsize;

}
@@ -903,18 +952,13 @@ __releases(&fc->lock) 
 * request_end().  Otherwise add it to the processing list, and set

 * the 'sent' flag.

 */

static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,

			      unsigned long nr_segs, loff_t pos)

static ssize_t fuse_dev_do_read(struct fuse_conn *fc, struct file *file,

				struct fuse_copy_state *cs, size_t nbytes)

{

	int err;

	struct fuse_req *req;

	struct fuse_in *in;

	struct fuse_copy_state cs;

	unsigned reqsize;

	struct file *file = iocb->ki_filp;

	struct fuse_conn *fc = fuse_get_conn(file);

	if (!fc)

		return -EPERM;



 restart:

	spin_lock(&fc->lock);
@@ -934,7 +978,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov, 
	if (!list_empty(&fc->interrupts)) {

		req = list_entry(fc->interrupts.next, struct fuse_req,

				 intr_entry);

		return fuse_read_interrupt(fc, req, iov, nr_segs);

		return fuse_read_interrupt(fc, cs, nbytes, req);

	}



	req = list_entry(fc->pending.next, struct fuse_req, list);
@@ -944,7 +988,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov, 
	in = &req->in;

	reqsize = in->h.len;

	/* If request is too large, reply with an error and restart the read */

	if (iov_length(iov, nr_segs) < reqsize) {

	if (nbytes < reqsize) {

		req->out.h.error = -EIO;

		/* SETXATTR is special, since it may contain too large data */

		if (in->h.opcode == FUSE_SETXATTR)
@@ -953,12 +997,12 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov, 
		goto restart;

	}

	spin_unlock(&fc->lock);

	fuse_copy_init(&cs, fc, 1, req, iov, nr_segs);

	err = fuse_copy_one(&cs, &in->h, sizeof(in->h));

	cs->req = req;

	err = fuse_copy_one(cs, &in->h, sizeof(in->h));

	if (!err)

		err = fuse_copy_args(&cs, in->numargs, in->argpages,

		err = fuse_copy_args(cs, in->numargs, in->argpages,

				     (struct fuse_arg *) in->args, 0);

	fuse_copy_finish(&cs);

	fuse_copy_finish(cs);

	spin_lock(&fc->lock);

	req->locked = 0;

	if (req->aborted) {
@@ -986,6 +1030,110 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov, 
	return err;

}



static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,

			      unsigned long nr_segs, loff_t pos)

{

	struct fuse_copy_state cs;

	struct file *file = iocb->ki_filp;

	struct fuse_conn *fc = fuse_get_conn(file);

	if (!fc)

		return -EPERM;



	fuse_copy_init(&cs, fc, 1, iov, nr_segs);



	return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));

}



static int fuse_dev_pipe_buf_steal(struct pipe_inode_info *pipe,

				   struct pipe_buffer *buf)

{

	return 1;

}



static const struct pipe_buf_operations fuse_dev_pipe_buf_ops = {

	.can_merge = 0,

	.map = generic_pipe_buf_map,

	.unmap = generic_pipe_buf_unmap,

	.confirm = generic_pipe_buf_confirm,

	.release = generic_pipe_buf_release,

	.steal = fuse_dev_pipe_buf_steal,

	.get = generic_pipe_buf_get,

};



static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,

				    struct pipe_inode_info *pipe,

				    size_t len, unsigned int flags)

{

	int ret;

	int page_nr = 0;

	int do_wakeup = 0;

	struct pipe_buffer *bufs;

	struct fuse_copy_state cs;

	struct fuse_conn *fc = fuse_get_conn(in);

	if (!fc)

		return -EPERM;



	bufs = kmalloc(pipe->buffers * sizeof (struct pipe_buffer), GFP_KERNEL);

	if (!bufs)

		return -ENOMEM;



	fuse_copy_init(&cs, fc, 1, NULL, 0);

	cs.pipebufs = bufs;

	cs.pipe = pipe;

	ret = fuse_dev_do_read(fc, in, &cs, len);

	if (ret < 0)

		goto out;



	ret = 0;

	pipe_lock(pipe);



	if (!pipe->readers) {

		send_sig(SIGPIPE, current, 0);

		if (!ret)

			ret = -EPIPE;

		goto out_unlock;

	}



	if (pipe->nrbufs + cs.nr_segs > pipe->buffers) {

		ret = -EIO;

		goto out_unlock;

	}



	while (page_nr < cs.nr_segs) {

		int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);

		struct pipe_buffer *buf = pipe->bufs + newbuf;



		buf->page = bufs[page_nr].page;

		buf->offset = bufs[page_nr].offset;

		buf->len = bufs[page_nr].len;

		buf->ops = &fuse_dev_pipe_buf_ops;



		pipe->nrbufs++;

		page_nr++;

		ret += buf->len;



		if (pipe->inode)

			do_wakeup = 1;

	}



out_unlock:

	pipe_unlock(pipe);



	if (do_wakeup) {

		smp_mb();

		if (waitqueue_active(&pipe->wait))

			wake_up_interruptible(&pipe->wait);

		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);

	}



out:

	for (; page_nr < cs.nr_segs; page_nr++)

		page_cache_release(bufs[page_nr].page);



	kfree(bufs);

	return ret;

}



static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,

			    struct fuse_copy_state *cs)

{
@@ -1246,7 +1394,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, const struct iovec *iov, 
	if (!fc)

		return -EPERM;



	fuse_copy_init(&cs, fc, 0, NULL, iov, nr_segs);

	fuse_copy_init(&cs, fc, 0, iov, nr_segs);



	return fuse_dev_do_write(fc, &cs, iov_length(iov, nr_segs));

}
@@ -1311,11 +1459,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe, 
	}

	pipe_unlock(pipe);



	memset(&cs, 0, sizeof(struct fuse_copy_state));

	cs.fc = fc;

	cs.write = 0;

	fuse_copy_init(&cs, fc, 0, NULL, nbuf);

	cs.pipebufs = bufs;

	cs.nr_segs = nbuf;

	cs.pipe = pipe;



	if (flags & SPLICE_F_MOVE)
@@ -1473,6 +1618,7 @@ const struct file_operations fuse_dev_operations = { 
	.llseek		= no_llseek,

	.read		= do_sync_read,

	.aio_read	= fuse_dev_read,

	.splice_read	= fuse_dev_splice_read,

	.write		= do_sync_write,

	.aio_write	= fuse_dev_write,

	.splice_write	= fuse_dev_splice_write,