// SPDX-License-Identifier: GPL-2.0-or-later/* Iterator helpers. * * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) */ #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){	struct bio_vec *bv = NULL;	struct page **pages;	unsigned int cur_npages;	unsigned int max_pages;	unsigned int npages = 0;	unsigned int i;	ssize_t ret;	size_t count = orig_len, offset, len;	size_t bv_size, pg_size; 	if (WARN_ON_ONCE(!iter_is_ubuf(orig) && !iter_is_iovec(orig)))		return -EIO; 	max_pages = iov_iter_npages(orig, INT_MAX);	bv_size = array_size(max_pages, sizeof(*bv));	bv = kvmalloc(bv_size, GFP_KERNEL);	if (!bv)		return -ENOMEM; 	/* Put the page list at the end of the bvec list storage.  bvec	 * elements are larger than page pointers, so as long as we work	 * 0->last, we should be fine.	 */	pg_size = array_size(max_pages, sizeof(*pages));	pages = (void *)bv + bv_size - pg_size; 	while (count && npages < max_pages) {		ret = iov_iter_extract_pages(orig, &pages, count,					     max_pages - npages, extraction_flags,					     &offset);		if (ret < 0) {			pr_err("Couldn't get user pages (rc=%zd)\n", ret);			break;		} 		if (ret > count) {			pr_err("get_pages rc=%zd more than %zu\n", ret, count);			break;		} 		count -= ret;		ret += offset;		cur_npages = DIV_ROUND_UP(ret, PAGE_SIZE); 		if (npages + cur_npages > max_pages) {			pr_err("Out of bvec array capacity (%u vs %u)\n",			       npages + cur_npages, max_pages);			break;		} 		for (i = 0; i < cur_npages; i++) {			len = ret > PAGE_SIZE ? PAGE_SIZE : ret;			bvec_set_page(bv + npages + i, *pages++, len - offset, offset);			ret -= len;			offset = 0;		} 		npages += cur_npages;	} 	iov_iter_bvec(new, orig->data_source, bv, npages, orig_len - count);	return npages;}EXPORT_SYMBOL_GPL(netfs_extract_user_iter);