From: Sage Weil <sage@newdream.net>
Date: Fri, 10 Sep 2010 19:57:46 +0000 (-0700)
Subject: mds: don't xlock and wrlock same dn->versionlock
X-Git-Tag: v0.22~185
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=fb96c17c0f2b721e3c44bbe07141fb16d00c4adf;p=ceph.git

mds: don't xlock and wrlock same dn->versionlock

We deadlock if we try to wrlock and xlock the same lock.  This was
happening during multi-mds rename when the versionlock was in the xlock
set.

Signed-off-by: Sage Weil <sage@newdream.net>
---

diff --git a/src/mds/Locker.cc b/src/mds/Locker.cc
index fafda5ffa5f8..f4772f03c72c 100644
--- a/src/mds/Locker.cc
+++ b/src/mds/Locker.cc
@@ -167,6 +167,10 @@ bool Locker::acquire_locks(MDRequest *mdr,
     // augment xlock with a versionlock?
     if ((*p)->get_type() == CEPH_LOCK_DN) {
       CDentry *dn = (CDentry*)(*p)->get_parent();
+
+      if (xlocks.count(&dn->versionlock))
+	continue;  // we're xlocking the versionlock too; don't wrlock it!
+
       if (mdr->is_master()) {
 	// master.  wrlock versionlock so we can pipeline dentry updates to journal.
 	wrlocks.insert(&dn->versionlock);