Commit 908a1ad8 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle)
Browse files

iov_iter: Handle compound highmem pages in copy_page_from_iter_atomic() 



copy_page_from_iter_atomic() already handles !highmem compound
pages correctly, but if we are passed a highmem compound page,
each base page needs to be mapped & unmapped individually.

Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Tested-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent f7f9a0c8

lib/iov_iter.c

+23 −10
Original line number Diff line number Diff line
@@ -566,24 +566,37 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i) 
}

EXPORT_SYMBOL(iov_iter_zero);



size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,

				  struct iov_iter *i)

size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,

		size_t bytes, struct iov_iter *i)

{

	char *p;

	size_t n, copied = 0;



	if (!page_copy_sane(page, offset, bytes))

		return 0;

	if (WARN_ON_ONCE(!i->data_source))

		return 0;



	do {

		char *p;



		n = bytes - copied;

		if (PageHighMem(page)) {

			page += offset / PAGE_SIZE;

			offset %= PAGE_SIZE;

			n = min_t(size_t, n, PAGE_SIZE - offset);

		}



		p = kmap_atomic(page) + offset;

	iterate_and_advance(i, bytes, base, len, off,

		iterate_and_advance(i, n, base, len, off,

			copyin(p + off, base, len),

			memcpy_from_iter(i, p + off, base, len)

		)

		kunmap_atomic(p);

		copied += n;

		offset += n;

	} while (PageHighMem(page) && copied != bytes && n > 0);



	return bytes;

	return copied;

}

EXPORT_SYMBOL(copy_page_from_iter_atomic);