ocfs2: Fix a race in o2dlm lockres mastery (14741472) · Commits · 戴 / test

In o2dlm, the master of a lock resource keeps a map of all interested nodes. This prevents the master from purging the resource before an interested node can create a lock. A race between the mastery thread and the mastery handler allowed an interested node to discover who the master is without informing the master directly. This is easily fixed by holding the dlm spinlock a little longer in the mastery handler. Signed-off-by:

Srinivas Eeda <srinivas.eeda@oracle.com> Signed-off-by:

Joel Becker <joel.becker@oracle.com>

fs/ocfs2/dlm/dlmmaster.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -1875,7 +1875,6 @@ int dlm_assert_master_handler(struct o2net_msg msg, u32 len, void data,
		ok:
		spin_unlock(&res->spinlock);
		}
		spin_unlock(&dlm->spinlock);

		// mlog(0, "woo! got an assert_master from node %u!\n",
		// assert->node_idx);
		@@ -1926,7 +1925,6 @@ ok:
		/* master is known, detach if not already detached.
		* ensures that only one assert_master call will happen
		* on this mle. */
		spin_lock(&dlm->spinlock);
		spin_lock(&dlm->master_lock);

		rr = atomic_read(&mle->mle_refs.refcount);
		@@ -1959,7 +1957,6 @@ ok:
		__dlm_put_mle(mle);
		}
		spin_unlock(&dlm->master_lock);
		spin_unlock(&dlm->spinlock);
		} else if (res) {
		if (res->owner != assert->node_idx) {
		mlog(0, "assert_master from %u, but current "
		@@ -1967,6 +1964,7 @@ ok:
		res->owner, namelen, name);
		}
		}
		spin_unlock(&dlm->spinlock);

		done:
		ret = 0;

Admin message