From: Timo Sirainen <tss@iki.fi>
Date: Mon, 19 Apr 2010 13:31:50 +0000 (+0300)
Subject: mdbox: Added a comment about how expunging works.
X-Git-Tag: 2.0.beta5~103
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c977374bd4651cafc1626ebe308aa66dfd8b30e0;p=thirdparty%2Fdovecot%2Fcore.git

mdbox: Added a comment about how expunging works.

--HG--
branch : HEAD
---

diff --git a/src/lib-storage/index/dbox-multi/mdbox-sync.c b/src/lib-storage/index/dbox-multi/mdbox-sync.c
index d1705a000f..b9bfa25a4e 100644
--- a/src/lib-storage/index/dbox-multi/mdbox-sync.c
+++ b/src/lib-storage/index/dbox-multi/mdbox-sync.c
@@ -1,5 +1,17 @@
 /* Copyright (c) 2007-2010 Dovecot authors, see the included COPYING file */
 
+/*
+   Expunging works like:
+
+   1. Lock map index by beginning a map sync.
+   2. Write map UID refcount changes to map index.
+   3. Expunge messages from mailbox index.
+   4. Finish map sync, which updates head=tail and unlocks map index.
+
+   If something crashes after 2 but before 4 is finished, head != tail and
+   reader can do a full resync to figure out what got broken.
+*/
+
 #include "lib.h"
 #include "array.h"
 #include "ioloop.h"