From b802bcf7040110e1f0768d9d9ffa88dabd4bd5e7 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@symas.com>
Date: Thu, 5 Jul 2012 16:40:46 -0700
Subject: [PATCH] Partial revert of 13c663f666ac28d7a72cbe644d393fc8d2dd9881
Don't re-use free pages so soon; that leaves us vulnerable to
DB corruption if data syncs successfully but meta doesn't.
---
libraries/libmdb/mdb.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 3b0b66fa19..fe89a7a45a 100644
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -1220,7 +1220,11 @@ mdb_page_alloc(MDB_cursor *mc, int num)
pgno_t pgno = P_INVALID;
MDB_ID2 mid;
- if (txn->mt_txnid > 2) {
+ /* The free list won't have any content at all until txn 2 has
+ * committed. The pages from txn 1 will be free after txn 3 has
+ * committed. It will be safe to re-use them during txn 4.
+ */
+ if (txn->mt_txnid > 3) {
if (!txn->mt_env->me_pghead &&
txn->mt_dbs[FREE_DBI].md_root != P_INVALID) {
@@ -1253,7 +1257,7 @@ again:
{
unsigned int i;
- oldest = txn->mt_txnid - 1;
+ oldest = txn->mt_txnid - 2;
for (i=0; i<txn->mt_env->me_txns->mti_numreaders; i++) {
txnid_t mr = txn->mt_env->me_txns->mti_readers[i].mr_txnid;
if (mr && mr < oldest)
--
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