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

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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: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2013-12-04 12:07:09 +01:00 committed by Philipp Reisner
parent 28995af5cf
commit 35b5ed5bba
1 changed files with 13 additions and 5 deletions
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18
drivers/block/drbd/drbd_req.c
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@ -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);
}