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Message-Id: <1363713419-17803-8-git-send-email-philipp.reisner@linbit.com>
Date: Tue, 19 Mar 2013 18:16:48 +0100
From: Philipp Reisner <philipp.reisner@...bit.com>
To: linux-kernel@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>, drbd-dev@...ts.linbit.com,
lars.ellenberg@...bit.com
Subject: [PATCH 07/18] drbd: Clarify when activity log I/O is delegated to the worker thread
From: Lars Ellenberg <lars.ellenberg@...bit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
drivers/block/drbd/drbd_actlog.c | 49 ++++++++++++++++++++----------------
drivers/block/drbd/drbd_int.h | 2 +-
drivers/block/drbd/drbd_receiver.c | 2 +-
drivers/block/drbd/drbd_req.c | 2 +-
drivers/block/drbd/drbd_worker.c | 2 +-
5 files changed, 31 insertions(+), 26 deletions(-)
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index c79625a..82199d9 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -104,7 +104,7 @@ struct update_al_work {
int err;
};
-static int al_write_transaction(struct drbd_conf *mdev);
+static int al_write_transaction(struct drbd_conf *mdev, bool delegate);
void *drbd_md_get_buffer(struct drbd_conf *mdev)
{
@@ -246,7 +246,10 @@ static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
return al_ext;
}
-void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
+/*
+ * @delegate: delegate activity log I/O to the worker thread
+ */
+void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i, bool delegate)
{
/* for bios crossing activity log extent boundaries,
* we may need to activate two extents in one go */
@@ -255,6 +258,17 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
unsigned enr;
bool locked = false;
+ /* When called through generic_make_request(), we must delegate
+ * activity log I/O to the worker thread: a further request
+ * submitted via generic_make_request() within the same task
+ * would be queued on current->bio_list, and would only start
+ * after this function returns (see generic_make_request()).
+ *
+ * However, if we *are* the worker, we must not delegate to ourselves.
+ */
+
+ if (delegate)
+ BUG_ON(current == mdev->tconn->worker.task);
D_ASSERT(first <= last);
D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
@@ -270,13 +284,6 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
(locked = lc_try_lock_for_transaction(mdev->act_log)));
if (locked) {
- /* drbd_al_write_transaction(mdev,al_ext,enr);
- * recurses into generic_make_request(), which
- * disallows recursion, bios being serialized on the
- * current->bio_tail list now.
- * we have to delegate updates to the activity log
- * to the worker thread. */
-
/* Double check: it may have been committed by someone else,
* while we have been waiting for the lock. */
if (mdev->act_log->pending_changes) {
@@ -287,7 +294,7 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
rcu_read_unlock();
if (write_al_updates) {
- al_write_transaction(mdev);
+ al_write_transaction(mdev, delegate);
mdev->al_writ_cnt++;
}
@@ -495,20 +502,18 @@ static int w_al_write_transaction(struct drbd_work *w, int unused)
/* Calls from worker context (see w_restart_disk_io()) need to write the
transaction directly. Others came through generic_make_request(),
those need to delegate it to the worker. */
-static int al_write_transaction(struct drbd_conf *mdev)
+static int al_write_transaction(struct drbd_conf *mdev, bool delegate)
{
- struct update_al_work al_work;
-
- if (current == mdev->tconn->worker.task)
+ if (delegate) {
+ struct update_al_work al_work;
+ init_completion(&al_work.event);
+ al_work.w.cb = w_al_write_transaction;
+ al_work.w.mdev = mdev;
+ drbd_queue_work_front(&mdev->tconn->sender_work, &al_work.w);
+ wait_for_completion(&al_work.event);
+ return al_work.err;
+ } else
return _al_write_transaction(mdev);
-
- init_completion(&al_work.event);
- al_work.w.cb = w_al_write_transaction;
- al_work.w.mdev = mdev;
- drbd_queue_work_front(&mdev->tconn->sender_work, &al_work.w);
- wait_for_completion(&al_work.event);
-
- return al_work.err;
}
static int _try_lc_del(struct drbd_conf *mdev, struct lc_element *al_ext)
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 6eecdec..453fccf 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1598,7 +1598,7 @@ extern const char *drbd_conn_str(enum drbd_conns s);
extern const char *drbd_role_str(enum drbd_role s);
/* drbd_actlog.c */
-extern void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i);
+extern void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i, bool delegate);
extern void drbd_al_complete_io(struct drbd_conf *mdev, struct drbd_interval *i);
extern void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector);
extern int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 8172a2c..1921871 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2265,7 +2265,7 @@ static int receive_Data(struct drbd_tconn *tconn, struct packet_info *pi)
drbd_set_out_of_sync(mdev, peer_req->i.sector, peer_req->i.size);
peer_req->flags |= EE_CALL_AL_COMPLETE_IO;
peer_req->flags &= ~EE_MAY_SET_IN_SYNC;
- drbd_al_begin_io(mdev, &peer_req->i);
+ drbd_al_begin_io(mdev, &peer_req->i, true);
}
err = drbd_submit_peer_request(mdev, peer_req, rw, DRBD_FAULT_DT_WR);
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 2b8303a..7d1ff1a 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1054,7 +1054,7 @@ void __drbd_make_request(struct drbd_conf *mdev, struct bio *bio, unsigned long
if (rw == WRITE && req->private_bio && req->i.size
&& !test_bit(AL_SUSPENDED, &mdev->flags)) {
req->rq_state |= RQ_IN_ACT_LOG;
- drbd_al_begin_io(mdev, &req->i);
+ drbd_al_begin_io(mdev, &req->i, true);
}
spin_lock_irq(&mdev->tconn->req_lock);
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 34b5d5d..f41e224 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1411,7 +1411,7 @@ int w_restart_disk_io(struct drbd_work *w, int cancel)
struct drbd_conf *mdev = w->mdev;
if (bio_data_dir(req->master_bio) == WRITE && req->rq_state & RQ_IN_ACT_LOG)
- drbd_al_begin_io(mdev, &req->i);
+ drbd_al_begin_io(mdev, &req->i, false);
drbd_req_make_private_bio(req, req->master_bio);
req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
--
1.7.9.5
--
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