ceph: queue cap_snaps once per realm (e8e1ba96) · Commits · 戴 / test

We were forming a dirty list, and then queueing cap_snaps for each realm _and_ its children, regardless of whether the children were already in the dirty list. This meant we did it twice for some realms. Which in turn meant we corrupted mdsc->snap_flush_list when the cap_snap was re-added to the list it was already on, and could trigger an infinite loop. We were also using recursion to do reach all the children, a no-no when stack is limited. Instead, (re)queue any children on the dirty list, avoiding processing anything twice and avoiding any recursion. Signed-off-by:

Sage Weil <sage@newdream.net>

fs/ceph/snap.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -584,10 +584,14 @@ static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
		if (lastinode)
		iput(lastinode);

		dout("queue_realm_cap_snaps %p %llx children\n", realm, realm->ino);
		list_for_each_entry(child, &realm->children, child_item)
		queue_realm_cap_snaps(child);
		list_for_each_entry(child, &realm->children, child_item) {
		dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
		realm, realm->ino, child, child->ino);
		list_del_init(&child->dirty_item);
		list_add(&child->dirty_item, &realm->dirty_item);
		}

		list_del_init(&realm->dirty_item);
		dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
		}

		@@ -683,7 +687,9 @@ more:
		* queue cap snaps _after_ we've built the new snap contexts,
		* so that i_head_snapc can be set appropriately.
		*/
		list_for_each_entry(realm, &dirty_realms, dirty_item) {
		while (!list_empty(&dirty_realms)) {
		realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
		dirty_item);
		queue_realm_cap_snaps(realm);
		}

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