Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 523ac9af authored by Al Viro's avatar Al Viro
Browse files

switch default_file_splice_read() to use of pipe-backed iov_iter 



we only use iov_iter_get_pages_alloc() and iov_iter_advance() -
pages are filled by kernel_readv() via a kvec array (as we used
to do all along), so iov_iter here is used only as a way of
arranging for those pages to be in pipe.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 82c156f8

fs/splice.c

+40 −71
Original line number Diff line number Diff line
@@ -361,7 +361,7 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = { 
};

EXPORT_SYMBOL(nosteal_pipe_buf_ops);



static ssize_t kernel_readv(struct file *file, const struct iovec *vec,

static ssize_t kernel_readv(struct file *file, const struct kvec *vec,

			    unsigned long vlen, loff_t offset)

{

	mm_segment_t old_fs;
@@ -397,96 +397,65 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos, 
				 struct pipe_inode_info *pipe, size_t len,

				 unsigned int flags)

{

	struct kvec *vec, __vec[PIPE_DEF_BUFFERS];

	struct iov_iter to;

	struct page **pages;

	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];

	size_t offset, dummy, copied = 0;

	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;

	}

	if (pipe->nrbufs == pipe->buffers)

		return -EAGAIN;



	/*

	 * Try to keep page boundaries matching to source pagecache ones -

	 * it probably won't be much help, but...

	 */

	offset = *ppos & ~PAGE_MASK;

	nr_pages = (len + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;



	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {

		struct page *page;

	iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);



		page = alloc_page(GFP_USER);

		error = -ENOMEM;

		if (!page)

			goto err;

	res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &dummy);

	if (res <= 0)

		return -ENOMEM;



		this_len = min_t(size_t, len, PAGE_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;

	}

	nr_pages = res / PAGE_SIZE;



	res = kernel_readv(in, vec, spd.nr_pages, *ppos);

	if (res < 0) {

		error = res;

		goto err;

	vec = __vec;

	if (nr_pages > PIPE_DEF_BUFFERS) {

		vec = kmalloc(nr_pages * sizeof(struct kvec), GFP_KERNEL);

		if (unlikely(!vec)) {

			res = -ENOMEM;

			goto out;

		}

	}



	error = 0;

	if (!res)

		goto err;

	pipe->bufs[to.idx].offset = offset;

	pipe->bufs[to.idx].len -= offset;



	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;

	for (i = 0; i < nr_pages; i++) {

		size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);

		vec[i].iov_base = page_address(pages[i]) + offset;

		vec[i].iov_len = this_len;

		len -= this_len;

		offset = 0;

	}

	spd.nr_pages -= nr_freed;



	res = splice_to_pipe(pipe, &spd);

	if (res > 0)

	res = kernel_readv(in, vec, nr_pages, *ppos);

	if (res > 0) {

		copied = res;

		*ppos += res;

	}



shrink_ret:

	if (vec != __vec)

		kfree(vec);

	splice_shrink_spd(&spd);

out:

	for (i = 0; i < nr_pages; i++)

		put_page(pages[i]);

	kvfree(pages);

	iov_iter_advance(&to, copied);	/* truncates and discards */

	return res;



err:

	for (i = 0; i < spd.nr_pages; i++)

		__free_page(spd.pages[i]);



	res = error;

	goto shrink_ret;

}



/*