Commit cfa320f7 authored by Keith Busch's avatar Keith Busch Committed by Jens Axboe
Browse files

iov: introduce iov_iter_aligned 



The existing iov_iter_alignment() function returns the logical OR of
address and length. For cases where address and length need to be
considered separately, introduce a helper function that a caller can
specificy length and address masks that indicate if the iov is
unaligned.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220610195830.3574005-9-kbusch@fb.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9cfe3dde

include/linux/uio.h

+2 −0
Original line number Diff line number Diff line
@@ -219,6 +219,8 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i); 
#endif



size_t iov_iter_zero(size_t bytes, struct iov_iter *);

bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,

			unsigned len_mask);

unsigned long iov_iter_alignment(const struct iov_iter *i);

unsigned long iov_iter_gap_alignment(const struct iov_iter *i);

void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,

lib/iov_iter.c

+92 −0
Original line number Diff line number Diff line
@@ -1268,6 +1268,98 @@ void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count) 
}

EXPORT_SYMBOL(iov_iter_discard);



static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,

				   unsigned len_mask)

{

	size_t size = i->count;

	size_t skip = i->iov_offset;

	unsigned k;



	for (k = 0; k < i->nr_segs; k++, skip = 0) {

		size_t len = i->iov[k].iov_len - skip;



		if (len > size)

			len = size;

		if (len & len_mask)

			return false;

		if ((unsigned long)(i->iov[k].iov_base + skip) & addr_mask)

			return false;



		size -= len;

		if (!size)

			break;

	}

	return true;

}



static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,

				  unsigned len_mask)

{

	size_t size = i->count;

	unsigned skip = i->iov_offset;

	unsigned k;



	for (k = 0; k < i->nr_segs; k++, skip = 0) {

		size_t len = i->bvec[k].bv_len - skip;



		if (len > size)

			len = size;

		if (len & len_mask)

			return false;

		if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask)

			return false;



		size -= len;

		if (!size)

			break;

	}

	return true;

}



/**

 * iov_iter_is_aligned() - Check if the addresses and lengths of each segments

 * 	are aligned to the parameters.

 *

 * @i: &struct iov_iter to restore

 * @addr_mask: bit mask to check against the iov element's addresses

 * @len_mask: bit mask to check against the iov element's lengths

 *

 * Return: false if any addresses or lengths intersect with the provided masks

 */

bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,

			 unsigned len_mask)

{

	if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))

		return iov_iter_aligned_iovec(i, addr_mask, len_mask);



	if (iov_iter_is_bvec(i))

		return iov_iter_aligned_bvec(i, addr_mask, len_mask);



	if (iov_iter_is_pipe(i)) {

		unsigned int p_mask = i->pipe->ring_size - 1;

		size_t size = i->count;



		if (size & len_mask)

			return false;

		if (size && allocated(&i->pipe->bufs[i->head & p_mask])) {

			if (i->iov_offset & addr_mask)

				return false;

		}



		return true;

	}



	if (iov_iter_is_xarray(i)) {

		if (i->count & len_mask)

			return false;

		if ((i->xarray_start + i->iov_offset) & addr_mask)

			return false;

	}



	return true;

}

EXPORT_SYMBOL_GPL(iov_iter_is_aligned);



static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)

{

	unsigned long res = 0;