Commit a52cc685 authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

rbd: acquire header_rwsem just once in rbd_queue_workfn() 



Currently header_rwsem is acquired twice: once in rbd_dev_parent_get()
when the image request is being created and then in rbd_queue_workfn()
to capture mapping_size and snapc.  Introduce rbd_img_capture_header()
and move image request allocation so that header_rwsem can be acquired
just once.

Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 78b42a87

drivers/block/rbd.c

+31 −28
Original line number Diff line number Diff line
@@ -1601,10 +1601,8 @@ static bool rbd_dev_parent_get(struct rbd_device *rbd_dev) 
	if (!rbd_dev->parent_spec)

		return false;



	down_read(&rbd_dev->header_rwsem);

	if (rbd_dev->parent_overlap)

		counter = atomic_inc_return_safe(&rbd_dev->parent_ref);

	up_read(&rbd_dev->header_rwsem);



	if (counter < 0)

		rbd_warn(rbd_dev, "parent reference overflow");
@@ -1619,8 +1617,7 @@ static bool rbd_dev_parent_get(struct rbd_device *rbd_dev) 
 */

static struct rbd_img_request *rbd_img_request_create(

					struct rbd_device *rbd_dev,

					enum obj_operation_type op_type,

					struct ceph_snap_context *snapc)

					enum obj_operation_type op_type)

{

	struct rbd_img_request *img_request;
@@ -1630,13 +1627,6 @@ static struct rbd_img_request *rbd_img_request_create( 


	img_request->rbd_dev = rbd_dev;

	img_request->op_type = op_type;

	if (!rbd_img_is_write(img_request))

		img_request->snap_id = rbd_dev->spec->snap_id;

	else

		img_request->snapc = snapc;



	if (rbd_dev_parent_get(rbd_dev))

		img_request_layered_set(img_request);



	INIT_LIST_HEAD(&img_request->lock_item);

	INIT_LIST_HEAD(&img_request->object_extents);
@@ -1645,6 +1635,21 @@ static struct rbd_img_request *rbd_img_request_create( 
	return img_request;

}



static void rbd_img_capture_header(struct rbd_img_request *img_req)

{

	struct rbd_device *rbd_dev = img_req->rbd_dev;



	lockdep_assert_held(&rbd_dev->header_rwsem);



	if (rbd_img_is_write(img_req))

		img_req->snapc = ceph_get_snap_context(rbd_dev->header.snapc);

	else

		img_req->snap_id = rbd_dev->spec->snap_id;



	if (rbd_dev_parent_get(rbd_dev))

		img_request_layered_set(img_req);

}



static void rbd_img_request_destroy(struct rbd_img_request *img_request)

{

	struct rbd_obj_request *obj_request;
@@ -2825,17 +2830,21 @@ static int rbd_obj_read_object(struct rbd_obj_request *obj_req) 
static int rbd_obj_read_from_parent(struct rbd_obj_request *obj_req)

{

	struct rbd_img_request *img_req = obj_req->img_request;

	struct rbd_device *parent = img_req->rbd_dev->parent;

	struct rbd_img_request *child_img_req;

	int ret;



	child_img_req = rbd_img_request_create(img_req->rbd_dev->parent,

					       OBJ_OP_READ, NULL);

	child_img_req = rbd_img_request_create(parent, OBJ_OP_READ);

	if (!child_img_req)

		return -ENOMEM;



	__set_bit(IMG_REQ_CHILD, &child_img_req->flags);

	child_img_req->obj_request = obj_req;



	down_read(&parent->header_rwsem);

	rbd_img_capture_header(child_img_req);

	up_read(&parent->header_rwsem);



	dout("%s child_img_req %p for obj_req %p\n", __func__, child_img_req,

	     obj_req);
@@ -4686,7 +4695,6 @@ static void rbd_queue_workfn(struct work_struct *work) 
	struct request *rq = blk_mq_rq_from_pdu(work);

	struct rbd_device *rbd_dev = rq->q->queuedata;

	struct rbd_img_request *img_request;

	struct ceph_snap_context *snapc = NULL;

	u64 offset = (u64)blk_rq_pos(rq) << SECTOR_SHIFT;

	u64 length = blk_rq_bytes(rq);

	enum obj_operation_type op_type;
@@ -4739,28 +4747,24 @@ static void rbd_queue_workfn(struct work_struct *work) 


	blk_mq_start_request(rq);



	img_request = rbd_img_request_create(rbd_dev, op_type);

	if (!img_request) {

		result = -ENOMEM;

		goto err_rq;

	}

	img_request->rq = rq;



	down_read(&rbd_dev->header_rwsem);

	mapping_size = rbd_dev->mapping.size;

	if (op_type != OBJ_OP_READ) {

		snapc = rbd_dev->header.snapc;

		ceph_get_snap_context(snapc);

	}

	rbd_img_capture_header(img_request);

	up_read(&rbd_dev->header_rwsem);



	if (offset + length > mapping_size) {

		rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)", offset,

			 length, mapping_size);

		result = -EIO;

		goto err_rq;

	}



	img_request = rbd_img_request_create(rbd_dev, op_type, snapc);

	if (!img_request) {

		result = -ENOMEM;

		goto err_rq;

		goto err_img_request;

	}

	img_request->rq = rq;

	snapc = NULL; /* img_request consumes a ref */



	dout("%s rbd_dev %p img_req %p %s %llu~%llu\n", __func__, rbd_dev,

	     img_request, obj_op_name(op_type), offset, length);
@@ -4782,7 +4786,6 @@ err_rq: 
	if (result)

		rbd_warn(rbd_dev, "%s %llx at %llx result %d",

			 obj_op_name(op_type), length, offset, result);

	ceph_put_snap_context(snapc);

err:

	blk_mq_end_request(rq, errno_to_blk_status(result));

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE