On Tue, Apr 11, 2017 at 12:00 AM, Stefan Hajnoczi <stefa...@redhat.com> wrote:
> On Sun, Apr 09, 2017 at 08:37:40PM +0800, jemmy858...@gmail.com wrote:
>> From: Lidong Chen <lidongc...@tencent.com>
>>
>> BLOCK_SIZE is (1 << 20), qcow2 cluster size is 65536 by default,
>> this maybe cause the qcow2 file size is bigger after migration.
>> This patch check each cluster, use blk_pwrite_zeroes for each
>> zero cluster.
>>
>> Signed-off-by: Lidong Chen <lidongc...@tencent.com>
>> ---
>> migration/block.c | 38 ++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/migration/block.c b/migration/block.c
>> index 7734ff7..fe613db 100644
>> --- a/migration/block.c
>> +++ b/migration/block.c
>> @@ -885,6 +885,8 @@ static int block_load(QEMUFile *f, void *opaque, int
>> version_id)
>> int64_t total_sectors = 0;
>> int nr_sectors;
>> int ret;
>> + BlockDriverInfo bdi;
>> + int cluster_size;
>>
>> do {
>> addr = qemu_get_be64(f);
>> @@ -934,8 +936,40 @@ static int block_load(QEMUFile *f, void *opaque, int
>> version_id)
>> } else {
>> buf = g_malloc(BLOCK_SIZE);
>> qemu_get_buffer(f, buf, BLOCK_SIZE);
>> - ret = blk_pwrite(blk, addr * BDRV_SECTOR_SIZE, buf,
>> - nr_sectors * BDRV_SECTOR_SIZE, 0);
>> +
>> + ret = bdrv_get_info(blk_bs(blk), &bdi);
>> + cluster_size = bdi.cluster_size;
>> +
>> + if (ret == 0 && cluster_size > 0 &&
>> + cluster_size <= BLOCK_SIZE &&
>> + BLOCK_SIZE % cluster_size == 0) {
>
> How about:
>
> if (blk != blk_prev) {
> blk_prev = blk;
> total_sectors = blk_nb_sectors(blk);
> if (total_sectors <= 0) {
> error_report("Error getting length of block device %s",
> device_name);
> return -EINVAL;
> }
>
> blk_invalidate_cache(blk, &local_err);
> if (local_err) {
> error_report_err(local_err);
> return -EINVAL;
> }
>
> + ret = bdrv_get_info(blk_bs(blk), &bdi);
> + if (ret == 0 && cluster_size > 0 && cluster_size <= BLOCK_SIZE &&
> + BLOCK_SIZE % cluster_size == 0) {
> + zero_cluster_size = bdi.cluster_size;
> + } else {
> + zero_cluster_size = 0;
> + }
> }
>
> That way we only fetch the cluster size once per device.
>
> When processing a block we do without repeatedly fetching the cluster
> size:
>
> if (zero_cluster_size) {
> ...detect zeroes...
> }
good idea, i will test again for this patch.
>
>> + int i;
>> + int64_t cur_addr;
>> + uint8_t *cur_buf;
>> +
>> + for (i = 0; i < BLOCK_SIZE / cluster_size; i++) {
>> + cur_addr = addr * BDRV_SECTOR_SIZE
>> + + i * cluster_size;
>> + cur_buf = buf + i * cluster_size;
>> +
>> + if (buffer_is_zero(cur_buf, cluster_size)) {
>> + ret = blk_pwrite_zeroes(blk, cur_addr,
>> + cluster_size,
>> + BDRV_REQ_MAY_UNMAP);
>> + } else {
>> + ret = blk_pwrite(blk, cur_addr, cur_buf,
>> + cluster_size, 0);
>
> Indentation is off here.
>
>> + }
>> +
>> + if (ret < 0) {
>> + g_free(buf);
>> + return ret;
>> + }
>> + }
>> + } else {
>> + ret = blk_pwrite(blk, addr * BDRV_SECTOR_SIZE, buf,
>> + nr_sectors * BDRV_SECTOR_SIZE, 0);
>> + }
>> g_free(buf);
>> }
>>
>> --
>> 1.8.3.1
>>
