Note: These patches apply to my block-next tree. You can also grab the code from git here: git://github.com/stefanha/qemu.git block-backup-core
This series adds a new QMP command, drive-backup, which takes a point-in-time snapshot of a block device. The snapshot is copied out to a target block device. A simple example is: drive-backup device=virtio0 format=qcow2 target=backup-20130401.qcow2 The original drive-backup blockjob was written by Dietmar Maurer <diet...@proxmox.com>. He is currently busy but I feel the feature is worth pushing into QEMU since there has been interest. This is my version of his patch, plus the QMP command and qemu-iotests test case. QMP 'transaction' support is included since v3. It adds support for atomic snapshots of multiple block devices. I also added an 'abort' transaction to allow testing of the .abort()/.cleanup() code path. Thanks to Wenchao for making qmp_transaction() extensible. How is this different from block-stream and drive-mirror? --------------------------------------------------------- Both block-stream and drive-mirror do not provide immediate point-in-time snapshots. Instead they copy data into a new file and then switch to it. In other words, the point at which the "snapshot" is taken cannot be controlled directly. drive-backup intercepts guest writes and saves data into the target block device before it is overwritten. The target block device can be a raw image file, backing files are not used to implement this feature. How can drive-backup be used? ----------------------------- The simplest use-case is to copy a point-in-time snapshot to a local file. More advanced users may wish to make the target an NBD URL. The NBD server listening on the other side can process the backup writes any way it wishes. I previously posted an RFC series with a backup server that streamed Dietmar's VMA backup archive format. What's next for drive-backup? ----------------------------- 1. Sync modes like drive-mirror (top, full, none). This makes it possible to preserve the backing file chain. v4: * Use notifier lists and BdrvTrackedRequest instead of custom callbacks [bonzini] * Add drive-backup QMP example JSON [eblake] * Add "Since: 1.6" to QMP schema changes [eblake] v3: * Rename to drive-backup for consistency with drive-mirror [kwolf] * Add QMP transaction support [kwolf] * Introduce bdrv_add_before_write_cb() to hook writes * Mention 'query-block-jobs' lists job of type 'backup' [eblake] * Rename rwlock to flush_rwlock [kwolf] * Fix space in block/backup.c comment [kwolf] v2: * s/block_backup/block-backup/ in commit message [eblake] * Avoid funny spacing in QMP docs [eblake] * Document query-block-jobs and block-job-cancel usage [eblake] Dietmar Maurer (1): block: add basic backup support to block driver Stefan Hajnoczi (7): block: add bdrv_add_before_write_notifier() block: add drive-backup QMP command qemu-iotests: add 055 drive-backup test case blockdev: rename BlkTransactionStates to singular blockdev: add DriveBackup transaction blockdev: add Abort transaction qemu-iotests: test 'drive-backup' transaction in 055 block.c | 18 ++- block/Makefile.objs | 1 + block/backup.c | 283 ++++++++++++++++++++++++++++++++++++ blockdev.c | 264 +++++++++++++++++++++++++++------- include/block/block_int.h | 38 ++++- qapi-schema.json | 69 ++++++++- qmp-commands.hx | 37 +++++ tests/qemu-iotests/055 | 348 +++++++++++++++++++++++++++++++++++++++++++++ tests/qemu-iotests/055.out | 5 + tests/qemu-iotests/group | 1 + 10 files changed, 1000 insertions(+), 64 deletions(-) create mode 100644 block/backup.c create mode 100755 tests/qemu-iotests/055 create mode 100644 tests/qemu-iotests/055.out -- 1.8.1.4