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block: convert bio_map_user_iov 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 visible to/affected by
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/20230522205744.2825689-7-dhowells@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
David Howells 2023-05-22 21:57:44 +01:00 committed by Jens Axboe
parent a7e689dd1c
commit 403b6fb8da
1 changed files with 11 additions and 12 deletions
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23
block/blk-map.c
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@ -281,22 +281,21 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
if (blk_queue_pci_p2pdma(rq->q))
extraction_flags |= ITER_ALLOW_P2PDMA;
if (iov_iter_extract_will_pin(iter))
bio_set_flag(bio, BIO_PAGE_PINNED);
bio_set_flag(bio, BIO_PAGE_REFFED);
while (iov_iter_count(iter)) {
struct page **pages, *stack_pages[UIO_FASTIOV];
struct page *stack_pages[UIO_FASTIOV];
struct page **pages = stack_pages;
ssize_t bytes;
size_t offs;
int npages;
if (nr_vecs <= ARRAY_SIZE(stack_pages)) {
pages = stack_pages;
bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
nr_vecs, &offs, extraction_flags);
} else {
bytes = iov_iter_get_pages_alloc(iter, &pages,
LONG_MAX, &offs, extraction_flags);
}
if (nr_vecs > ARRAY_SIZE(stack_pages))
pages = NULL;
bytes = iov_iter_extract_pages(iter, &pages, LONG_MAX,
nr_vecs, extraction_flags, &offs);
if (unlikely(bytes <= 0)) {
ret = bytes ? bytes : -EFAULT;
goto out_unmap;
@ -318,7 +317,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
if (!bio_add_hw_page(rq->q, bio, page, n, offs,
max_sectors, &same_page)) {
if (same_page)
put_page(page);
bio_release_page(bio, page);
break;
}
@ -330,7 +329,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
* release the pages we didn't map into the bio, if any
*/
while (j < npages)
put_page(pages[j++]);
bio_release_page(bio, pages[j++]);
if (pages != stack_pages)
kvfree(pages);
/* couldn't stuff something into bio? */