From 35b5ed5bbac2432acdfce1d9dec8dbf8fe7d60dd Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Wed, 4 Dec 2013 12:07:09 +0100 Subject: [PATCH] drbd: reduce number of spinlock drop/re-aquire cycles 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 Signed-off-by: Lars Ellenberg --- drivers/block/drbd/drbd_req.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c index 09803d0..4c7fee1 100644 --- a/drivers/block/drbd/drbd_req.c +++ b/drivers/block/drbd/drbd_req.c @@ -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 @@ nodata: 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); } -- 2.7.4