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Date: Thu, 3 Jul 2014 10:42:57 +0200
From: Philipp Reisner <philipp.reisner@...bit.com>
To: linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Cc: drbd-dev@...ts.linbit.com
Subject: [PATCH 05/23] drbd: add lists to find oldest pending requests
From: Lars Ellenberg <lars.ellenberg@...bit.com>
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@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
drivers/block/drbd/drbd_int.h | 11 ++++++++++-
drivers/block/drbd/drbd_main.c | 7 ++++++-
drivers/block/drbd/drbd_req.c | 45 +++++++++++++++++++++++++++++++-----------
3 files changed, 49 insertions(+), 14 deletions(-)
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 08fa2dc..f29f107 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -318,6 +318,10 @@ struct drbd_request {
struct list_head tl_requests; /* ring list in the transfer log */
struct bio *master_bio; /* master bio pointer */
+ /* see struct drbd_device */
+ struct list_head req_pending_master_completion;
+ struct list_head req_pending_local;
+
/* for generic IO accounting */
unsigned long start_jif;
@@ -738,7 +742,7 @@ struct submit_worker {
struct workqueue_struct *wq;
struct work_struct worker;
- spinlock_t lock;
+ /* protected by ..->resource->req_lock */
struct list_head writes;
};
@@ -795,6 +799,11 @@ struct drbd_device {
struct rb_root read_requests;
struct rb_root write_requests;
+ /* for statistics and timeouts */
+ /* [0] read, [1] write */
+ struct list_head pending_master_completion[2];
+ struct list_head pending_completion[2];
+
/* use checksums for *this* resync */
bool use_csums;
/* blocks to resync in this run [unit BM_BLOCK_SIZE] */
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 0baec7a..5886596 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1934,6 +1934,10 @@ void drbd_init_set_defaults(struct drbd_device *device)
INIT_LIST_HEAD(&device->resync_work.list);
INIT_LIST_HEAD(&device->unplug_work.list);
INIT_LIST_HEAD(&device->bm_io_work.w.list);
+ INIT_LIST_HEAD(&device->pending_master_completion[0]);
+ INIT_LIST_HEAD(&device->pending_master_completion[1]);
+ INIT_LIST_HEAD(&device->pending_completion[0]);
+ INIT_LIST_HEAD(&device->pending_completion[1]);
device->resync_work.cb = w_resync_timer;
device->unplug_work.cb = w_send_write_hint;
@@ -2268,6 +2272,8 @@ static void do_retry(struct work_struct *ws)
}
}
+/* called via drbd_req_put_completion_ref(),
+ * holds resource->req_lock */
void drbd_restart_request(struct drbd_request *req)
{
unsigned long flags;
@@ -2687,7 +2693,6 @@ static int init_submitter(struct drbd_device *device)
return -ENOMEM;
INIT_WORK(&device->submit.worker, do_submit);
- spin_lock_init(&device->submit.lock);
INIT_LIST_HEAD(&device->submit.writes);
return 0;
}
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 1319bea..23cd909 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -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;
--
1.9.1
--
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