diff options
| -rw-r--r-- | source3/lib/dbwrap_ctdb.c | 121 |
1 files changed, 116 insertions, 5 deletions
diff --git a/source3/lib/dbwrap_ctdb.c b/source3/lib/dbwrap_ctdb.c index 0986083268..fb99e1d9cf 100644 --- a/source3/lib/dbwrap_ctdb.c +++ b/source3/lib/dbwrap_ctdb.c @@ -664,6 +664,65 @@ static NTSTATUS db_ctdb_delete_transaction(struct db_record *rec) return status; } +/** + * Fetch the db sequence number of a persistent db directly from the db. + */ +static NTSTATUS db_ctdb_fetch_db_seqnum_from_db(struct db_ctdb_ctx *db, + uint64_t *seqnum) +{ + NTSTATUS status; + const char *keyname = CTDB_DB_SEQNUM_KEY; + TDB_DATA key; + TDB_DATA data; + struct ctdb_ltdb_header header; + TALLOC_CTX *mem_ctx = talloc_stackframe(); + + if (seqnum == NULL) { + return NT_STATUS_INVALID_PARAMETER; + } + + key.dptr = (uint8_t *)discard_const(keyname); + key.dsize = strlen(keyname) + 1; + + status = db_ctdb_ltdb_fetch(db, key, &header, mem_ctx, &data); + if (!NT_STATUS_IS_OK(status)) { + goto done; + } + + if (data.dsize != sizeof(uint64_t)) { + *seqnum = 0; + goto done; + } + + *seqnum = *(uint64_t *)data.dptr; + +done: + TALLOC_FREE(mem_ctx); + return status; +} + +/** + * Store the database sequence number inside a transaction. + */ +static NTSTATUS db_ctdb_store_db_seqnum(struct db_ctdb_transaction_handle *h, + uint64_t seqnum) +{ + NTSTATUS status; + const char *keyname = CTDB_DB_SEQNUM_KEY; + TDB_DATA key; + TDB_DATA data; + + key.dptr = (uint8_t *)discard_const(keyname); + key.dsize = strlen(keyname); + + data.dptr = (uint8_t *)&seqnum; + data.dsize = sizeof(uint64_t); + + status = db_ctdb_transaction_store(h, key, data); + + return status; +} + /* commit a transaction */ @@ -674,6 +733,8 @@ static int db_ctdb_transaction_commit(struct db_context *db) NTSTATUS rets; int status; struct db_ctdb_transaction_handle *h = ctx->transaction; + uint64_t old_seqnum, new_seqnum; + int ret; if (h == NULL) { DEBUG(0,(__location__ " transaction commit with no open transaction on db 0x%08x\n", ctx->db_id)); @@ -693,6 +754,30 @@ static int db_ctdb_transaction_commit(struct db_context *db) DEBUG(5,(__location__ " Commit transaction on db 0x%08x\n", ctx->db_id)); + /* + * As the last db action before committing, bump the database sequence + * number. Note that this undoes all changes to the seqnum records + * performed under the transaction. This record is not meant to be + * modified by user interaction. It is for internal use only... + */ + rets = db_ctdb_fetch_db_seqnum_from_db(ctx, &old_seqnum); + if (!NT_STATUS_IS_OK(rets)) { + DEBUG(1, (__location__ " failed to fetch the db sequence number " + "in transaction commit on db 0x%08x\n", ctx->db_id)); + ret = -1; + goto done; + } + + new_seqnum = old_seqnum + 1; + + rets = db_ctdb_store_db_seqnum(h, new_seqnum); + if (!NT_STATUS_IS_OK(rets)) { + DEBUG(1, (__location__ "failed to store the db sequence number " + " in transaction commit on db 0x%08x\n", ctx->db_id)); + ret = -1; + goto done; + } + again: if (h->m_write == NULL) { /* no changes were made, potentially after a retry */ @@ -707,14 +792,40 @@ again: NULL, NULL, &status); if (!NT_STATUS_IS_OK(rets) || status != 0) { /* - * TODO: - * check the database sequence number and - * compare it to the seqnum after applying the - * marshall buffer. If it is the same: return success. + * The TRANS3_COMMIT control should only possibly fail when a + * recovery has been running concurrently. In any case, the db + * will be the same on all nodes, either the new copy or the + * old copy. This can be detected by comparing the old and new + * local sequence numbers. + */ + rets = db_ctdb_fetch_db_seqnum_from_db(ctx, &new_seqnum); + if (!NT_STATUS_IS_OK(rets)) { + DEBUG(1, (__location__ " failed to refetch db sequence " + "number after failed TRANS3_COMMIT\n")); + ret = -1; + goto done; + } + + if (new_seqnum == old_seqnum) { + /* Recovery prevented all our changes: retry. */ + goto again; + } else if (new_seqnum != (old_seqnum + 1)) { + DEBUG(0, (__location__ " ERROR: new_seqnum[%lu] != " + "old_seqnum[%lu] + (0 or 1) after failed " + "TRANS3_COMMIT - this should not happen!\n", + (unsigned long)new_seqnum, + (unsigned long)old_seqnum)); + ret = -1; + goto done; + } + /* + * Recovery propagated our changes to all nodes, completing + * our commit for us - succeed. */ - goto again; } + ret = 0; + done: h->ctx->transaction = NULL; talloc_free(h); |