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163 lines
5.4 KiB
163 lines
5.4 KiB
/* Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#include "sql_backup_lock.h"
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#include <utility>
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#include "m_string.h"
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#include "my_dbug.h"
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#include "my_inttypes.h"
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#include "my_sys.h"
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#include "mysqld_error.h" // ER_SPECIFIC_ACCESS_DENIED_ERROR
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#include "sql/auth/sql_security_ctx.h" // Security_context
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#include "sql/mdl.h"
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#include "sql/system_variables.h"
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#include "sql_class.h" // THD
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/**
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Check if a current user has the privilege BACKUP_ADMIN required to run
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the statement LOCK INSTANCE FOR BACKUP.
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@param thd Current thread
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@retval false A user has the privilege BACKUP_ADMIN
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@retval true A user doesn't have the privilege BACKUP_ADMIN
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*/
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static bool check_backup_admin_privilege(THD *thd) {
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Security_context *sctx = thd->security_context();
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if (!sctx->has_global_grant(STRING_WITH_LEN("BACKUP_ADMIN")).first) {
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my_error(ER_SPECIFIC_ACCESS_DENIED_ERROR, MYF(0), "BACKUP_ADMIN");
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return true;
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}
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return false;
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}
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bool Sql_cmd_lock_instance::execute(THD *thd) {
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if (check_backup_admin_privilege(thd) ||
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acquire_exclusive_backup_lock(
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thd,
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DBUG_EVALUATE_IF("stop_slave_dont_release_backup_lock", 5,
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thd->variables.lock_wait_timeout),
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false))
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return true;
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my_ok(thd);
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return false;
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}
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bool Sql_cmd_unlock_instance::execute(THD *thd) {
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if (check_backup_admin_privilege(thd)) return true;
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release_backup_lock(thd);
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my_ok(thd);
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return false;
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}
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/**
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Acquire either exclusive or shared Backup Lock.
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@param[in] thd Current thread context
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@param[in] mdl_type Type of metadata lock to acquire for backup
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@param[in] mdl_duration Duration of metadata lock
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@param[in] lock_wait_timeout How many seconds to wait before timeout.
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@return Operation status.
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@retval false Success
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@retval true Failure
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*/
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static bool acquire_mdl_for_backup(THD *thd, enum_mdl_type mdl_type,
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enum_mdl_duration mdl_duration,
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ulong lock_wait_timeout) {
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MDL_request mdl_request;
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DBUG_ASSERT(mdl_type == MDL_SHARED || mdl_type == MDL_INTENTION_EXCLUSIVE);
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MDL_REQUEST_INIT(&mdl_request, MDL_key::BACKUP_LOCK, "", "", mdl_type,
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mdl_duration);
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return thd->mdl_context.acquire_lock(&mdl_request, lock_wait_timeout);
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}
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/**
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MDL_release_locks_visitor subclass to release MDL for BACKUP_LOCK.
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*/
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class Release_all_backup_locks : public MDL_release_locks_visitor {
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public:
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virtual bool release(MDL_ticket *ticket) {
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return ticket->get_key()->mdl_namespace() == MDL_key::BACKUP_LOCK;
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}
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};
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void release_backup_lock(THD *thd) {
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Release_all_backup_locks lock_visitor;
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thd->mdl_context.release_locks(&lock_visitor);
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}
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/*
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The following rationale is for justification of choice for specific lock
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types to support BACKUP LOCK.
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IX and S locks are mutually incompatible. On the other hand both these
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lock types are compatible with themselves. IX lock has lower priority
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than S locks. So we can use S lock for rare Backup operation which should
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not be starved by more frequent DDL operations using IX locks.
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From all listed above follows that S lock should be considered as Exclusive
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Backup Lock and IX lock should be considered as Shared Backup Lock.
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*/
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bool acquire_exclusive_backup_lock(THD *thd, ulong lock_wait_timeout,
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bool for_trx) {
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enum_mdl_duration duration = (for_trx ? MDL_TRANSACTION : MDL_EXPLICIT);
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return acquire_mdl_for_backup(thd, MDL_SHARED, duration, lock_wait_timeout);
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}
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bool acquire_shared_backup_lock(THD *thd, ulong lock_wait_timeout,
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bool for_trx) {
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enum_mdl_duration duration = (for_trx ? MDL_TRANSACTION : MDL_EXPLICIT);
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return acquire_mdl_for_backup(thd, MDL_INTENTION_EXCLUSIVE, duration,
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lock_wait_timeout);
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}
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Is_instance_backup_locked_result is_instance_backup_locked(THD *thd) {
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Is_instance_backup_locked_result res;
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MDL_key key(MDL_key::BACKUP_LOCK, "", "");
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MDL_lock_is_owned_visitor backup_lock_owner;
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if (thd->mdl_context.find_lock_owner(&key, &backup_lock_owner))
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res = Is_instance_backup_locked_result::OOM;
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else {
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if (backup_lock_owner.exists())
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res = Is_instance_backup_locked_result::LOCKED;
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else
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res = Is_instance_backup_locked_result::NOT_LOCKED;
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}
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return res;
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}
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