From 13b9414b5798539e2dbb87a570d96184fe21edf4 Mon Sep 17 00:00:00 2001 From: Pavel Butsykin Date: Fri, 22 Jul 2016 11:17:52 +0300 Subject: drive-backup: added support for data compression The idea is simple - backup is "written-once" data. It is written block by block and it is large enough. It would be nice to save storage space and compress it. The patch adds a flag to the qmp/hmp drive-backup command which enables block compression. Compression should be implemented in the format driver to enable this feature. There are some limitations of the format driver to allow compressed writes. We can write data only once. Though for backup this is perfectly fine. These limitations are maintained by the driver and the error will be reported if we are doing something wrong. Signed-off-by: Pavel Butsykin Reviewed-by: Stefan Hajnoczi Signed-off-by: Denis V. Lunev CC: Jeff Cody CC: Markus Armbruster CC: Eric Blake CC: John Snow CC: Stefan Hajnoczi CC: Kevin Wolf Signed-off-by: Kevin Wolf --- block/backup.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'block/backup.c') diff --git a/block/backup.c b/block/backup.c index 2c0532314f..bb3bb9a9eb 100644 --- a/block/backup.c +++ b/block/backup.c @@ -47,6 +47,7 @@ typedef struct BackupBlockJob { uint64_t sectors_read; unsigned long *done_bitmap; int64_t cluster_size; + bool compress; NotifierWithReturn before_write; QLIST_HEAD(, CowRequest) inflight_reqs; } BackupBlockJob; @@ -154,7 +155,8 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job, bounce_qiov.size, BDRV_REQ_MAY_UNMAP); } else { ret = blk_co_pwritev(job->target, start * job->cluster_size, - bounce_qiov.size, &bounce_qiov, 0); + bounce_qiov.size, &bounce_qiov, + job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0); } if (ret < 0) { trace_backup_do_cow_write_fail(job, start, ret); @@ -477,6 +479,7 @@ static void coroutine_fn backup_run(void *opaque) void backup_start(const char *job_id, BlockDriverState *bs, BlockDriverState *target, int64_t speed, MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, + bool compress, BlockdevOnError on_source_error, BlockdevOnError on_target_error, BlockCompletionFunc *cb, void *opaque, @@ -507,6 +510,12 @@ void backup_start(const char *job_id, BlockDriverState *bs, return; } + if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) { + error_setg(errp, "Compression is not supported for this drive %s", + bdrv_get_device_name(target)); + return; + } + if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) { return; } @@ -555,6 +564,7 @@ void backup_start(const char *job_id, BlockDriverState *bs, job->sync_mode = sync_mode; job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ? sync_bitmap : NULL; + job->compress = compress; /* If there is no backing file on the target, we cannot rely on COW if our * backup cluster size is smaller than the target cluster size. Even for -- cgit v1.2.3