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dbwrap_ctdb: treat empty records in ltdb as non-existing

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When fetching records from remote ctdb nodes via ctdbd_parse() or in
db_ctdb_traverse(), we already check for tombstone records and skip
them. This was originally also done for the ltdb checks.

See also bug: https://bugzilla.samba.org/show_bug.cgi?id=10008
(commit 1cae59ce112ccb51b45357a52b902f80fce1eef1).

Commit 925625b52886d40b50fc631bad8bdc81970f7598 reverted part of the
patch of bug 10008 due to a deadlock it introduced.

This patch re-introduces the consistent treatment of empty records in
the ltdb but avoids the deadlock by correctly signalling
NT_STATUS_NOT_FOUND if an empty record is found authoritatively in
the ltdb and not calling ctdb in this case.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12005

Pair-Programmed-With: Michael Adam <obnox@samba.org>

Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Michael Adam <obnox@samba.org>

Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Tue Aug  9 04:38:44 CEST 2016 on sn-devel-144

(backported from commit 25df582739918b7afd4e5497eaffe279e2d92cd1)

Autobuild-User(v4-3-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-3-test): Wed Aug 10 14:58:12 CEST 2016 on sn-devel-104
This commit is contained in:
Ralph Boehme 2016-08-08 16:58:51 +02:00 committed by Karolin Seeger
parent f7718e4257
commit 68d13b1d50
1 changed files with 26 additions and 1 deletions
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27
source3/lib/dbwrap/dbwrap_ctdb.c
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@ -1213,6 +1213,7 @@ struct db_ctdb_parse_record_state {
void *private_data;
bool ask_for_readonly_copy;
bool done;
bool empty_record;
};
static void db_ctdb_parse_record_parser(
@ -1232,7 +1233,16 @@ static void db_ctdb_parse_record_parser_nonpersistent(
(struct db_ctdb_parse_record_state *)private_data;
if (db_ctdb_can_use_local_hdr(header, true)) {
state->parser(key, data, state->private_data);
/*
* A record consisting only of the ctdb header can be
* a validly created empty record or a tombstone
* record of a deleted record (not vacuumed yet). Mark
* it accordingly.
*/
state->empty_record = (data.dsize == 0);
if (!state->empty_record) {
state->parser(key, data, state->private_data);
}
state->done = true;
} else {
/*
@ -1257,6 +1267,7 @@ static NTSTATUS db_ctdb_parse_record(struct db_context *db, TDB_DATA key,
state.parser = parser;
state.private_data = private_data;
state.empty_record = false;
if (ctx->transaction != NULL) {
struct db_ctdb_transaction_handle *h = ctx->transaction;
@ -1288,6 +1299,20 @@ static NTSTATUS db_ctdb_parse_record(struct db_context *db, TDB_DATA key,
status = db_ctdb_ltdb_parse(
ctx, key, db_ctdb_parse_record_parser_nonpersistent, &state);
if (NT_STATUS_IS_OK(status) && state.done) {
if (state.empty_record) {
/*
* We know authoritatively, that this is an empty
* record. Since ctdb does not distinguish between empty
* and deleted records, this can be a record stored as
* empty or a not-yet-vacuumed tombstone record of a
* deleted record. Now Samba right now can live without
* empty records, so we can safely report this record
* as non-existing.
*
* See bugs 10008 and 12005.
*/
return NT_STATUS_NOT_FOUND;
}
return NT_STATUS_OK;
}