From 56392d2f40aac4b520fc50bc356f40e07f7e1c7d Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Tue, 19 Mar 2013 18:16:48 +0100 Subject: [PATCH] drbd: Clarify when activity log I/O is delegated to the worker thread Signed-off-by: Philipp Reisner Signed-off-by: Lars Ellenberg Signed-off-by: Jens Axboe --- 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 c79625aa8cf2..82199d9a9a61 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 6eecdec9da2b..453fccfc440c 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 8172a2cfdead..1921871ca9a8 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 2b8303ad63c9..7d1ff1aaeb71 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 34b5d5d23ac4..f41e224caa7c 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; -- 2.34.1