From: Sage Weil <sage@redhat.com>
Date: Mon, 13 Mar 2017 11:43:57 +0000 (-0400)
Subject: os/bluestore: prevent throttle deadlock due to deferred writes
X-Git-Tag: v12.0.1~12^2~14
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=3f9c21614587bb924ebe4bd4c9d960a27248e75a;p=ceph.git

os/bluestore: prevent throttle deadlock due to deferred writes

Kick off deferred IOs if we pass the throttle midpoint or if we would
block during submission.

Signed-off-by: Sage Weil <sage@redhat.com>
---

diff --git a/src/common/Throttle.h b/src/common/Throttle.h
index b07c9e47923..e4119a3b97c 100644
--- a/src/common/Throttle.h
+++ b/src/common/Throttle.h
@@ -66,6 +66,13 @@ public:
    */
   int64_t get_max() const { return max.read(); }
 
+  /**
+   * return true if past midpoint
+   */
+  bool past_midpoint() const {
+    return count.read() >= max.read() / 2;
+  }
+
   /**
    * set the new max number, and wait until the number of taken slots drains
    * and drops below this limit.
diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index 39803670b1f..2419d2e2dbb 100644
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -7665,7 +7665,9 @@ void BlueStore::_kv_sync_thread()
 
       if (!deferred_aggressive) {
 	std::lock_guard<std::mutex> l(deferred_lock);
-	if (deferred_queue_size >= (int)g_conf->bluestore_deferred_batch_ops) {
+	if (deferred_queue_size >= (int)g_conf->bluestore_deferred_batch_ops ||
+	    throttle_deferred_ops.past_midpoint() ||
+	    throttle_deferred_bytes.past_midpoint()) {
 	  _deferred_try_submit();
 	}
       }
@@ -7958,8 +7960,15 @@ int BlueStore::queue_transactions(
   throttle_ops.get(txc->ops);
   throttle_bytes.get(txc->bytes);
   if (txc->deferred_txn) {
-    throttle_deferred_ops.get(txc->ops);
-    throttle_deferred_bytes.get(txc->bytes);
+    // ensure we do not block here because of deferred writes
+    if (!throttle_deferred_ops.get_or_fail(txc->ops)) {
+      deferred_try_submit();
+      throttle_deferred_ops.get(txc->ops);
+    }
+    if (!throttle_deferred_bytes.get_or_fail(txc->bytes)) {
+      deferred_try_submit();
+      throttle_deferred_bytes.get(txc->bytes);
+    }
   }
 
   if (handle)
diff --git a/src/os/bluestore/BlueStore.h b/src/os/bluestore/BlueStore.h
index 106e9ccf38f..39913a98b34 100644
--- a/src/os/bluestore/BlueStore.h
+++ b/src/os/bluestore/BlueStore.h
@@ -1856,6 +1856,10 @@ private:
 
   bluestore_deferred_op_t *_get_deferred_op(TransContext *txc, OnodeRef o);
   void _deferred_queue(TransContext *txc);
+  void deferred_try_submit() {
+    std::lock_guard<std::mutex> l(deferred_lock);
+    _deferred_try_submit();
+  }
   void _deferred_try_submit();
   void _deferred_try_submit(OpSequencer *osr);
   int _deferred_finish(TransContext *txc);