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rbd: acquire header_rwsem just once in rbd_queue_workfn()

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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 <idryomov@gmail.com>
This commit is contained in:
Ilya Dryomov 2020-02-12 15:08:39 +01:00
parent 78b42a871a
commit a52cc68575
1 changed files with 31 additions and 28 deletions
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59
drivers/block/rbd.c
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@ -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));
}