From a52cc685753568e5bcbe762586c2bfbe7175255e Mon Sep 17 00:00:00 2001 From: Ilya Dryomov Date: Wed, 12 Feb 2020 15:08:39 +0100 Subject: [PATCH] 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: Ilya Dryomov --- drivers/block/rbd.c | 59 ++++++++++++++++++++++++--------------------- 1 file changed, 31 insertions(+), 28 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index c61c5dd424fa..acda61f5be03 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -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; @@ -4739,29 +4747,25 @@ 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; + goto err_img_request; } - img_request = rbd_img_request_create(rbd_dev, op_type, snapc); - if (!img_request) { - result = -ENOMEM; - goto err_rq; - } - 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)); }