qemu/migration/savevm.h
Fam Zheng a1fbe750fd migration: Fix race of image locking between src and dst
Previously, dst side will immediately try to lock the write byte upon
receiving QEMU_VM_EOF, but at src side, bdrv_inactivate_all() is only
done after sending it. If the src host is under load, dst may fail to
acquire the lock due to racing with the src unlocking it.

Fix this by hoisting the bdrv_inactivate_all() operation before
QEMU_VM_EOF.

N.B. A further improvement could possibly be done to cleanly handover
locks between src and dst, so that there is no window where a third QEMU
could steal the locks and prevent src and dst from running.

N.B. This commit includes a minor improvement to the error handling
by using qemu_file_set_error().

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 20170616160658.32290-1-famz@redhat.com
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[PMM: noted qemu_file_set_error() use in commit as suggested by Daniel]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2017-06-19 17:53:33 +01:00

58 lines
2.1 KiB
C

/*
* QEMU save vm functions
*
* Copyright (c) 2003-2008 Fabrice Bellard
* Copyright (c) 2009-2017 Red Hat Inc
*
* Authors:
* Juan Quintela <quintela@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef MIGRATION_SAVEVM_H
#define MIGRATION_SAVEVM_H
#define QEMU_VM_FILE_MAGIC 0x5145564d
#define QEMU_VM_FILE_VERSION_COMPAT 0x00000002
#define QEMU_VM_FILE_VERSION 0x00000003
#define QEMU_VM_EOF 0x00
#define QEMU_VM_SECTION_START 0x01
#define QEMU_VM_SECTION_PART 0x02
#define QEMU_VM_SECTION_END 0x03
#define QEMU_VM_SECTION_FULL 0x04
#define QEMU_VM_SUBSECTION 0x05
#define QEMU_VM_VMDESCRIPTION 0x06
#define QEMU_VM_CONFIGURATION 0x07
#define QEMU_VM_COMMAND 0x08
#define QEMU_VM_SECTION_FOOTER 0x7e
bool qemu_savevm_state_blocked(Error **errp);
void qemu_savevm_state_begin(QEMUFile *f);
void qemu_savevm_state_header(QEMUFile *f);
int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy);
void qemu_savevm_state_cleanup(void);
void qemu_savevm_state_complete_postcopy(QEMUFile *f);
int qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only,
bool inactivate_disks);
void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
uint64_t *res_non_postcopiable,
uint64_t *res_postcopiable);
void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
void qemu_savevm_send_open_return_path(QEMUFile *f);
int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len);
void qemu_savevm_send_postcopy_advise(QEMUFile *f);
void qemu_savevm_send_postcopy_listen(QEMUFile *f);
void qemu_savevm_send_postcopy_run(QEMUFile *f);
void qemu_savevm_send_postcopy_ram_discard(QEMUFile *f, const char *name,
uint16_t len,
uint64_t *start_list,
uint64_t *length_list);
int qemu_loadvm_state(QEMUFile *f);
#endif