linux/fs/netfs/iterator.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Iterator helpers.
 *
 * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 */

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/scatterlist.h>
#include <linux/netfs.h>
#include "internal.h"

/**
 * netfs_extract_user_iter - Extract the pages from a user iterator into a bvec
 * @orig: The original iterator
 * @orig_len: The amount of iterator to copy
 * @new: The iterator to be set up
 * @extraction_flags: Flags to qualify the request
 *
 * Extract the page fragments from the given amount of the source iterator and
 * build up a second iterator that refers to all of those bits.  This allows
 * the original iterator to disposed of.
 *
 * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be
 * allowed on the pages extracted.
 *
 * On success, the number of elements in the bvec is returned, the original
 * iterator will have been advanced by the amount extracted.
 *
 * The iov_iter_extract_mode() function should be used to query how cleanup
 * should be performed.
 */
ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
				struct iov_iter *new,
				iov_iter_extraction_t extraction_flags)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Select the span of a bvec iterator we're going to use.  Limit it by both maximum
 * size and maximum number of segments.  Returns the size of the span in bytes.
 */
static size_t netfs_limit_bvec(const struct iov_iter *iter, size_t start_offset,
			       size_t max_size, size_t max_segs)
{ … }

/*
 * Select the span of an xarray iterator we're going to use.  Limit it by both
 * maximum size and maximum number of segments.  It is assumed that segments
 * can be larger than a page in size, provided they're physically contiguous.
 * Returns the size of the span in bytes.
 */
static size_t netfs_limit_xarray(const struct iov_iter *iter, size_t start_offset,
				 size_t max_size, size_t max_segs)
{ … }

size_t netfs_limit_iter(const struct iov_iter *iter, size_t start_offset,
			size_t max_size, size_t max_segs)
{ … }
EXPORT_SYMBOL(…);