Cleanup MDB_env.me_txn0.

More fallout from 4d02c741b120786df1b87ee9ed49c1d3f9bc7522.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 4a5b7f0..cfce8a1 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -2640,6 +2640,7 @@ mdb_txn_renew0(MDB_txn *txn)
                        meta = env->me_metas[txn->mt_txnid & 1];
                }
        } else {
+               /* Not yet touching txn == env->me_txn0, it may be active */
                if (ti) {
                        if (LOCK_MUTEX(rc, env, MDB_MUTEX(env, w)))
                                return rc;
@@ -2722,7 +2723,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 {
        MDB_txn *txn;
        MDB_ntxn *ntxn;
-       int rc, size, tsize = sizeof(MDB_txn);
+       int rc, size, tsize;
 
        flags &= MDB_TXN_BEGIN_FLAGS;
        flags |= env->me_flags & MDB_WRITEMAP;
@@ -2733,6 +2734,8 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
        }
        if (env->me_flags & MDB_RDONLY & ~flags) /* write txn in RDONLY env */
                return EACCES;
+
+       size = tsize = sizeof(MDB_txn);
        if (parent) {
                /* Nested transactions: Max 1 child, write txns only, no writemap */
                flags |= parent->mt_flags;
@@ -2741,16 +2744,15 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
                {
                        return (parent->mt_flags & MDB_TXN_RDONLY) ? EINVAL : MDB_BAD_TXN;
                }
-               tsize = sizeof(MDB_ntxn);
-       }
-       size = tsize;
-       if (!(flags & MDB_RDONLY)) {
-               if (!parent) {
-                       txn = env->me_txn0;     /* just reuse preallocated write txn */
-                       goto ok;
-               }
-               /* child txns use own copy of cursors */
+               /* Child txns save MDB_pgstate and use own copy of cursors */
+               size = tsize = sizeof(MDB_ntxn);
                size += env->me_maxdbs * sizeof(MDB_cursor *);
+       } else if (!(flags & MDB_RDONLY)) {
+               /* Reuse preallocated write txn. However, do not touch it until
+                * mdb_txn_renew0() succeeds, since it currently may be active.
+                */
+               txn = env->me_txn0;
+               goto renew;
        }
        size += env->me_maxdbs * (sizeof(MDB_db)+1);
 
@@ -2775,7 +2777,6 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
        txn->mt_flags = flags;
        txn->mt_env = env;
 
-ok:
        if (parent) {
                unsigned int i;
                txn->mt_u.dirty_list = malloc(sizeof(MDB_ID2)*MDB_IDL_UM_SIZE);
@@ -2815,6 +2816,7 @@ ok:
                if (rc)
                        mdb_txn_reset0(txn, "beginchild-fail");
        } else {
+renew:
                rc = mdb_txn_renew0(txn);
        }
        if (rc) {
@@ -4732,15 +4734,13 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
                        if (rc)
                                goto leave;
                }
-               if (!((flags & MDB_RDONLY) ||
-                         (env->me_pbuf = calloc(1, env->me_psize))))
-                       rc = ENOMEM;
                if (!(flags & MDB_RDONLY)) {
                        MDB_txn *txn;
                        int tsize = sizeof(MDB_txn), size = tsize + env->me_maxdbs *
                                (sizeof(MDB_db)+sizeof(MDB_cursor *)+sizeof(unsigned int)+1);
-                       txn = calloc(1, size);
-                       if (txn) {
+                       if ((env->me_pbuf = calloc(1, env->me_psize)) &&
+                               (txn = calloc(1, size)))
+                       {
                                txn->mt_dbs = (MDB_db *)((char *)txn + tsize);
                                txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
                                txn->mt_dbiseqs = (unsigned int *)(txn->mt_cursors + env->me_maxdbs);