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drbd: add lists to find oldest pending requests

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Adding requests to per-device fifo lists as soon as possible after
allocating them leaves a simple list_first_entry_or_null() to find the
oldest request, regardless what it is still waiting for.

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
2013-11-22 12:52:03 +01:00
committed by Philipp Reisner
parent e5f891b223
commit 844a6ae735
3 changed files with 49 additions and 14 deletions
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45
drivers/block/drbd/drbd_req.c
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@@ -84,6 +84,8 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
INIT_LIST_HEAD(&req->tl_requests);
INIT_LIST_HEAD(&req->w.list);
INIT_LIST_HEAD(&req->req_pending_master_completion);
INIT_LIST_HEAD(&req->req_pending_local);
/* one reference to be put by __drbd_make_request */
atomic_set(&req->completion_ref, 1);
@@ -120,12 +122,14 @@ void drbd_req_destroy(struct kref *kref)
return;
}
/* remove it from the transfer log.
* well, only if it had been there in the first
* place... if it had not (local only or conflicting
* and never sent), it should still be "empty" as
* initialized in drbd_req_new(), so we can list_del() it
* here unconditionally */
/* If called from mod_rq_state (expected normal case) or
* drbd_send_and_submit (the less likely normal path), this holds the
* req_lock, and req->tl_requests will typicaly be on ->transfer_log,
* though it may be still empty (never added to the transfer log).
*
* If called from do_retry(), we do NOT hold the req_lock, but we are
* still allowed to unconditionally list_del(&req->tl_requests),
* because it will be on a local on-stack list only. */
list_del_init(&req->tl_requests);
/* finally remove the request from the conflict detection
@@ -312,8 +316,15 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
if (req->i.waiting)
wake_up(&device->misc_wait);
/* Either we are about to complete to upper layers,
* or we will restart this request.
* In either case, the request object will be destroyed soon,
* so better remove it from all lists. */
list_del_init(&req->req_pending_master_completion);
}
/* still holds resource->req_lock */
static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
{
struct drbd_device *device = req->device;
@@ -400,6 +411,7 @@ static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
++k_put;
else
++c_put;
list_del_init(&req->req_pending_local);
}
if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
@@ -1070,9 +1082,11 @@ drbd_submit_req_private_bio(struct drbd_request *req)
static void drbd_queue_write(struct drbd_device *device, struct drbd_request *req)
{
spin_lock(&device->submit.lock);
spin_lock_irq(&device->resource->req_lock);
list_add_tail(&req->tl_requests, &device->submit.writes);
spin_unlock(&device->submit.lock);
list_add_tail(&req->req_pending_master_completion,
&device->pending_master_completion[1 /* WRITE */]);
spin_unlock_irq(&device->resource->req_lock);
queue_work(device->submit.wq, &device->submit.worker);
}
@@ -1186,8 +1200,15 @@ static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request
no_remote = true;
}
/* If it took the fast path in drbd_request_prepare, add it here.
* The slow path has added it already. */
if (list_empty(&req->req_pending_master_completion))
list_add_tail(&req->req_pending_master_completion,
&device->pending_master_completion[rw == WRITE]);
if (req->private_bio) {
/* needs to be marked within the same spinlock */
list_add_tail(&req->req_pending_local,
&device->pending_completion[rw == WRITE]);
_req_mod(req, TO_BE_SUBMITTED);
/* but we need to give up the spinlock to submit */
submit_private_bio = true;
@@ -1278,9 +1299,9 @@ void do_submit(struct work_struct *ws)
struct drbd_request *req, *tmp;
for (;;) {
spin_lock(&device->submit.lock);
spin_lock_irq(&device->resource->req_lock);
list_splice_tail_init(&device->submit.writes, &incoming);
spin_unlock(&device->submit.lock);
spin_unlock_irq(&device->resource->req_lock);
submit_fast_path(device, &incoming);
if (list_empty(&incoming))
@@ -1304,9 +1325,9 @@ skip_fast_path:
if (list_empty(&device->submit.writes))
break;
spin_lock(&device->submit.lock);
spin_lock_irq(&device->resource->req_lock);
list_splice_tail_init(&device->submit.writes, &more_incoming);
spin_unlock(&device->submit.lock);
spin_unlock_irq(&device->resource->req_lock);
if (list_empty(&more_incoming))
break;