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idl: Optionally warn when writing to read-write columns.

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ovs-vswitchd should only write to write-only columns.  Furthermore,
writing to a column which is not write-only can cause serious
performance degradations.  This patch causes ovs-vswitchd to log
and reject writes to read-write columns.

Signed-off-by: Ethan Jackson <ethan@nicira.com>
This commit is contained in:
Ethan Jackson
2012-09-20 11:13:15 -07:00
parent 3b4c362f40
commit 8cdec72569
3 changed files with 24 additions and 3 deletions
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25
lib/ovsdb-idl.c
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@@ -70,6 +70,7 @@ struct ovsdb_idl {
struct json *monitor_request_id;
unsigned int last_monitor_request_seqno;
unsigned int change_seqno;
bool verify_write_only;
/* Database locking. */
char *lock_name; /* Name of lock we need, NULL if none. */
@@ -402,6 +403,16 @@ ovsdb_idl_force_reconnect(struct ovsdb_idl *idl)
{
jsonrpc_session_force_reconnect(idl->session);
}
/* Some IDL users should only write to write-only columns. Furthermore,
* writing to a column which is not write-only can cause serious performance
* degradations for these users. This function causes 'idl' to reject writes
* to columns which are not marked write only using ovsdb_idl_omit_alert(). */
void
ovsdb_idl_verify_write_only(struct ovsdb_idl *idl)
{
idl->verify_write_only = true;
}
static unsigned char *
ovsdb_idl_get_mode(struct ovsdb_idl *idl,
@@ -1824,6 +1835,7 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
struct ovsdb_idl_row *row = CONST_CAST(struct ovsdb_idl_row *, row_);
const struct ovsdb_idl_table_class *class;
size_t column_idx;
bool write_only;
if (ovsdb_idl_row_is_synthetic(row)) {
ovsdb_datum_destroy(datum, &column->type);
@@ -1832,12 +1844,20 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
class = row->table->class;
column_idx = column - class->columns;
write_only = row->table->modes[column_idx] == OVSDB_IDL_MONITOR;
assert(row->new != NULL);
assert(column_idx < class->n_columns);
assert(row->old == NULL ||
row->table->modes[column_idx] & OVSDB_IDL_MONITOR);
if (row->table->idl->verify_write_only && !write_only) {
VLOG_ERR("Bug: Attempt to write to a read/write column (%s:%s) when"
" explicitly configured not to.", class->name, column->name);
ovsdb_datum_destroy(datum, &column->type);
return;
}
/* If this is a write-only column and the datum being written is the same
* as the one already there, just skip the update entirely. This is worth
* optimizing because we have a lot of columns that get periodically
@@ -1849,9 +1869,8 @@ ovsdb_idl_txn_write(const struct ovsdb_idl_row *row_,
* transaction only does writes of existing values, without making any real
* changes, we will drop the whole transaction later in
* ovsdb_idl_txn_commit().) */
if (row->table->modes[column_idx] == OVSDB_IDL_MONITOR
&& ovsdb_datum_equals(ovsdb_idl_read(row, column),
datum, &column->type)) {
if (write_only && ovsdb_datum_equals(ovsdb_idl_read(row, column),
datum, &column->type)) {
ovsdb_datum_destroy(datum, &column->type);
return;
}