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block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages

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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: David Howells <dhowells@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John 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: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230522205744.2825689-6-dhowells@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
David Howells 2023-05-22 21:57:43 +01:00 committed by Jens Axboe
parent fd363244e8
commit a7e689dd1c
1 changed files with 12 additions and 11 deletions
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23
block/bio.c
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@ -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,
UINT_MAX - bio->bi_iter.bi_size,
nr_pages, &offset, extraction_flags);
size = iov_iter_extract_pages(iter, &pages,
UINT_MAX - bio->bi_iter.bi_size,
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));