Commit a7e689dd authored by David Howells's avatar David Howells Committed by Jens Axboe
Browse files

block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages 



This will pin pages or leave them unaltered rather than getting a ref on
them as appropriate to the iterator.

The pages need to be pinned for DIO rather than having refs taken on them to
prevent VM copy-on-write from malfunctioning during a concurrent fork() (the
result of the I/O could otherwise end up being affected by/visible to the
child process).

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Jan Kara <jack@suse.cz>
cc: Matthew Wilcox <willy@infradead.org>
cc: Logan Gunthorpe <logang@deltatee.com>
cc: linux-block@vger.kernel.org
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230522205744.2825689-6-dhowells@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fd363244

block/bio.c

+12 −11
Original line number Diff line number Diff line
@@ -1205,7 +1205,7 @@ static int bio_iov_add_page(struct bio *bio, struct page *page, 
	}



	if (same_page)

		put_page(page);

		bio_release_page(bio, page);

	return 0;

}
@@ -1219,7 +1219,7 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page, 
			queue_max_zone_append_sectors(q), &same_page) != len)

		return -EINVAL;

	if (same_page)

		put_page(page);

		bio_release_page(bio, page);

	return 0;

}
@@ -1230,10 +1230,10 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page, 
 * @bio: bio to add pages to

 * @iter: iov iterator describing the region to be mapped

 *

 * Pins pages from *iter and appends them to @bio's bvec array. The

 * pages will have to be released using put_page() when done.

 * For multi-segment *iter, this function only adds pages from the

 * next non-empty segment of the iov iterator.

 * Extracts pages from *iter and appends them to @bio's bvec array.  The pages

 * will have to be cleaned up in the way indicated by the BIO_PAGE_PINNED flag.

 * For a multi-segment *iter, this function only adds pages from the next

 * non-empty segment of the iov iterator.

 */

static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)

{
@@ -1265,9 +1265,9 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) 
	 * result to ensure the bio's total size is correct. The remainder of

	 * the iov data will be picked up in the next bio iteration.

	 */

	size = iov_iter_get_pages(iter, pages,

	size = iov_iter_extract_pages(iter, &pages,

				      UINT_MAX - bio->bi_iter.bi_size,

				  nr_pages, &offset, extraction_flags);

				      nr_pages, extraction_flags, &offset);

	if (unlikely(size <= 0))

		return size ? size : -EFAULT;
@@ -1300,7 +1300,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) 
	iov_iter_revert(iter, left);

out:

	while (i < nr_pages)

		put_page(pages[i++]);

		bio_release_page(bio, pages[i++]);



	return ret;

}
@@ -1335,7 +1335,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) 
		return 0;

	}



	bio_set_flag(bio, BIO_PAGE_REFFED);

	if (iov_iter_extract_will_pin(iter))

		bio_set_flag(bio, BIO_PAGE_PINNED);

	do {

		ret = __bio_iov_iter_get_pages(bio, iter);

	} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));