[SCM] Samba Shared Repository - branch master updated

[Michael Adam]

The branch, master has been updated
       via  8812148 s3:dbwrap_ctdb: fix non-locked fetch on persistent db's causing corruption
      from  68529bc s3-charcnv: remove unused labels.

http://gitweb.samba.org/?p=samba.git;a=shortlog;h=master


- Log -----------------------------------------------------------------
commit 8812148e2436b5ad9120181797e432285ccbb983
Author: Michael Adam <obnox at samba.org>
Date:   Fri Mar 25 00:29:42 2011 +0100

    s3:dbwrap_ctdb: fix non-locked fetch on persistent db's causing corruption
    
    When doing a non-locking fetch on a record of a persistent db when no
    transaction is running, the old behaviour was to fetch locally and
    do a ctdb call when the record was not found in the local db.
    The call is useless for persistent dbs anyway since they are only
    written to using transactions and hence kept in sync, but it is
    also harmful, because a ctdb call will bump the record RSN when it
    does actually migrate the record from one node to another.
    
    Recently, ctdb has been changed to make all calls do a migration.
    This uncovered the client misbehaviour for persistent dbs, because
    now _each_ non-locking fetch will render the persistent db inconsistent:
    A subsequent transaction which touches the record in question will
    fail because the RSNs are out of sync.
    
    This patch fixes this old bug.
    
    Autobuild-User: Michael Adam <obnox at samba.org>
    Autobuild-Date: Fri Mar 25 01:26:32 CET 2011 on sn-devel-104

-----------------------------------------------------------------------

Summary of changes:
 source3/lib/dbwrap_ctdb.c |   36 ++++++++++++++++++++++++++++++++++--
 1 files changed, 34 insertions(+), 2 deletions(-)


Changeset truncated at 500 lines:

diff --git a/source3/lib/dbwrap_ctdb.c b/source3/lib/dbwrap_ctdb.c
index 67425dc..46ec6de 100644
--- a/source3/lib/dbwrap_ctdb.c
+++ b/source3/lib/dbwrap_ctdb.c
@@ -474,6 +474,34 @@ static int db_ctdb_transaction_fetch(struct db_ctdb_ctx *db,
 	return 0;
 }
 
+/**
+ * Fetch a record from a persistent database
+ * without record locking and without an active transaction.
+ *
+ * This just fetches from the local database copy.
+ * Since the databases are kept in syc cluster-wide,
+ * there is no point in doing a ctdb call to fetch the
+ * record from the lmaster. It does even harm since migration
+ * of records bump their RSN and hence render the persistent
+ * database inconsistent.
+ */
+static int db_ctdb_fetch_persistent(struct db_ctdb_ctx *db,
+				    TALLOC_CTX *mem_ctx,
+				    TDB_DATA key, TDB_DATA *data)
+{
+	NTSTATUS status;
+	bool found;
+
+	status = db_ctdb_ltdb_fetch(db, key, NULL, mem_ctx, data);
+
+	if (NT_STATUS_EQUAL(status, NT_STATUS_NOT_FOUND)) {
+		*data = tdb_null;
+	} else if (!NT_STATUS_IS_OK(status)) {
+		return -1;
+	}
+
+	return 0;
+}
 
 static NTSTATUS db_ctdb_store_transaction(struct db_record *rec, TDB_DATA data, int flag);
 static NTSTATUS db_ctdb_delete_transaction(struct db_record *rec);
@@ -1075,6 +1103,10 @@ static int db_ctdb_fetch(struct db_context *db, TALLOC_CTX *mem_ctx,
 		return db_ctdb_transaction_fetch(ctx, mem_ctx, key, data);
 	}
 
+	if (db->persistent) {
+		return db_ctdb_fetch_persistent(ctx, mem_ctx, key, data);
+	}
+
 	/* try a direct fetch */
 	ctdb_data = tdb_fetch(ctx->wtdb->tdb, key);
 
@@ -1085,8 +1117,8 @@ static int db_ctdb_fetch(struct db_context *db, TALLOC_CTX *mem_ctx,
 	 */
 	if ((ctdb_data.dptr != NULL) &&
 	    (ctdb_data.dsize >= sizeof(struct ctdb_ltdb_header)) &&
-	    (db->persistent ||
-	     ((struct ctdb_ltdb_header *)ctdb_data.dptr)->dmaster == get_my_vnn())) {
+	    ((struct ctdb_ltdb_header *)ctdb_data.dptr)->dmaster == get_my_vnn())
+	{
 		/* we are the dmaster - avoid the ctdb protocol op */
 
 		data->dsize = ctdb_data.dsize - sizeof(struct ctdb_ltdb_header);


-- 
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