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Commit 35b5ed5b authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
Browse files

drbd: reduce number of spinlock drop/re-aquire cycles 



Instead of dropping and re-aquiring the spinlock around the submit,
just remember that we want to submit, and do that only once we have
dropped the spinlock for good.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 28995af5

drivers/block/drbd/drbd_req.c

+14 −6
Original line number Diff line number Diff line
@@ -1086,11 +1086,13 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long 


static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request *req)

{

	struct drbd_resource *resource = device->resource;

	const int rw = bio_rw(req->master_bio);

	struct bio_and_error m = { NULL, };

	bool no_remote = false;

	bool submit_private_bio = false;



	spin_lock_irq(&device->resource->req_lock);

	spin_lock_irq(&resource->req_lock);

	if (rw == WRITE) {

		/* This may temporarily give up the req_lock,

		 * but will re-aquire it before it returns here.
@@ -1152,9 +1154,7 @@ static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request 
		/* needs to be marked within the same spinlock */

		_req_mod(req, TO_BE_SUBMITTED);

		/* but we need to give up the spinlock to submit */

		spin_unlock_irq(&device->resource->req_lock);

		drbd_submit_req_private_bio(req);

		spin_lock_irq(&device->resource->req_lock);

		submit_private_bio = true;

	} else if (no_remote) {

nodata:

		if (__ratelimit(&drbd_ratelimit_state))
@@ -1167,8 +1167,16 @@ static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request 
out:

	if (drbd_req_put_completion_ref(req, &m, 1))

		kref_put(&req->kref, drbd_req_destroy);

	spin_unlock_irq(&device->resource->req_lock);



	spin_unlock_irq(&resource->req_lock);



	/* Even though above is a kref_put(), this is safe.

	 * As long as we still need to submit our private bio,

	 * we hold a completion ref, and the request cannot disappear.

	 * If however this request did not even have a private bio to submit

	 * (e.g. remote read), req may already be invalid now.

	 * That's why we cannot check on req->private_bio. */

	if (submit_private_bio)

		drbd_submit_req_private_bio(req);

	if (m.bio)

		complete_master_bio(device, &m);

}