Commit 8cd54c1c authored by Al Viro's avatar Al Viro
Browse files

iov_iter: separate direction from flavour 



Instead of having them mixed in iter->type, use separate ->iter_type
and ->data_source (u8 and bool resp.)  And don't bother with (pseudo-)
bitmap for the former - microoptimizations from being able to check
if the flavour is one of two values are not worth the confusion for
optimizer.  It can't prove that we never get e.g. ITER_IOVEC | ITER_PIPE,
so we end up with extra headache.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 556351c1

include/linux/uio.h

+10 −14
Original line number Diff line number Diff line
@@ -19,21 +19,17 @@ struct kvec { 


enum iter_type {

	/* iter types */

	ITER_IOVEC = 4,

	ITER_KVEC = 8,

	ITER_BVEC = 16,

	ITER_PIPE = 32,

	ITER_DISCARD = 64,

	ITER_XARRAY = 128,

	ITER_IOVEC,

	ITER_KVEC,

	ITER_BVEC,

	ITER_PIPE,

	ITER_XARRAY,

	ITER_DISCARD,

};



struct iov_iter {

	/*

	 * Bit 0 is the read/write bit, set if we're writing.

	 * Bit 1 is the BVEC_FLAG_NO_REF bit, set if type is a bvec and

	 * the caller isn't expecting to drop a page reference when done.

	 */

	unsigned int type;

	u8 iter_type;

	bool data_source;

	size_t iov_offset;

	size_t count;

	union {
@@ -55,7 +51,7 @@ struct iov_iter { 


static inline enum iter_type iov_iter_type(const struct iov_iter *i)

{

	return i->type & ~(READ | WRITE);

	return i->iter_type;

}



static inline bool iter_is_iovec(const struct iov_iter *i)
@@ -90,7 +86,7 @@ static inline bool iov_iter_is_xarray(const struct iov_iter *i) 


static inline unsigned char iov_iter_rw(const struct iov_iter *i)

{

	return i->type & (READ | WRITE);

	return i->data_source ? WRITE : READ;

}



/*

lib/iov_iter.c

+48 −37
Original line number Diff line number Diff line
@@ -489,19 +489,15 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, 
			size_t count)

{

	WARN_ON(direction & ~(READ | WRITE));

	direction &= READ | WRITE;



	/* It will get better.  Eventually... */

	if (uaccess_kernel()) {

		i->type = ITER_KVEC | direction;

		i->kvec = (struct kvec *)iov;

	} else {

		i->type = ITER_IOVEC | direction;

		i->iov = iov;

	}

	i->nr_segs = nr_segs;

	i->iov_offset = 0;

	i->count = count;

	WARN_ON_ONCE(uaccess_kernel());

	*i = (struct iov_iter) {

		.iter_type = ITER_IOVEC,

		.data_source = direction,

		.iov = iov,

		.nr_segs = nr_segs,

		.iov_offset = 0,

		.count = count

	};

}

EXPORT_SYMBOL(iov_iter_init);
@@ -1218,11 +1214,14 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction, 
			size_t count)

{

	WARN_ON(direction & ~(READ | WRITE));

	i->type = ITER_KVEC | (direction & (READ | WRITE));

	i->kvec = kvec;

	i->nr_segs = nr_segs;

	i->iov_offset = 0;

	i->count = count;

	*i = (struct iov_iter){

		.iter_type = ITER_KVEC,

		.data_source = direction,

		.kvec = kvec,

		.nr_segs = nr_segs,

		.iov_offset = 0,

		.count = count

	};

}

EXPORT_SYMBOL(iov_iter_kvec);
@@ -1231,11 +1230,14 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction, 
			size_t count)

{

	WARN_ON(direction & ~(READ | WRITE));

	i->type = ITER_BVEC | (direction & (READ | WRITE));

	i->bvec = bvec;

	i->nr_segs = nr_segs;

	i->iov_offset = 0;

	i->count = count;

	*i = (struct iov_iter){

		.iter_type = ITER_BVEC,

		.data_source = direction,

		.bvec = bvec,

		.nr_segs = nr_segs,

		.iov_offset = 0,

		.count = count

	};

}

EXPORT_SYMBOL(iov_iter_bvec);
@@ -1245,12 +1247,15 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction, 
{

	BUG_ON(direction != READ);

	WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));

	i->type = ITER_PIPE | READ;

	i->pipe = pipe;

	i->head = pipe->head;

	i->iov_offset = 0;

	i->count = count;

	i->start_head = i->head;

	*i = (struct iov_iter){

		.iter_type = ITER_PIPE,

		.data_source = false,

		.pipe = pipe,

		.head = pipe->head,

		.start_head = pipe->head,

		.iov_offset = 0,

		.count = count

	};

}

EXPORT_SYMBOL(iov_iter_pipe);
@@ -1271,11 +1276,14 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction, 
		     struct xarray *xarray, loff_t start, size_t count)

{

	BUG_ON(direction & ~1);

	i->type = ITER_XARRAY | (direction & (READ | WRITE));

	i->xarray = xarray;

	i->xarray_start = start;

	i->count = count;

	i->iov_offset = 0;

	*i = (struct iov_iter) {

		.iter_type = ITER_XARRAY,

		.data_source = direction,

		.xarray = xarray,

		.xarray_start = start,

		.count = count,

		.iov_offset = 0

	};

}

EXPORT_SYMBOL(iov_iter_xarray);
@@ -1291,9 +1299,12 @@ EXPORT_SYMBOL(iov_iter_xarray); 
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)

{

	BUG_ON(direction != READ);

	i->type = ITER_DISCARD | READ;

	i->count = count;

	i->iov_offset = 0;

	*i = (struct iov_iter){

		.iter_type = ITER_DISCARD,

		.data_source = false,

		.count = count,

		.iov_offset = 0

	};

}

EXPORT_SYMBOL(iov_iter_discard);