Commit 3928d50b authored by Lidong Chen's avatar Lidong Chen Committed by Stefan Hajnoczi
Browse files

migration/block: use blk_pwrite_zeroes for each zero cluster 



BLOCK_SIZE is (1 << 20), qcow2 cluster size is 65536 by default,
this may cause the qcow2 file size to be bigger after migration.
This patch checks each cluster, using blk_pwrite_zeroes for each
zero cluster.

[Initialize cluster_size to BLOCK_SIZE to prevent a gcc uninitialized
variable compiler warning.  In reality we always initialize cluster_size
in a conditional but gcc doesn't know that.
--Stefan]

Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarLidong Chen <lidongchen@tencent.com>
Message-id: 1492050868-16200-1-git-send-email-lidongchen@tencent.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent d72915c6

migration/block.c

+33 −2
Original line number Diff line number Diff line
@@ -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 = BLOCK_SIZE;



    do {

        addr = qemu_get_be64(f);
@@ -919,6 +921,15 @@ static int block_load(QEMUFile *f, void *opaque, int version_id) 
                    error_report_err(local_err);

                    return -EINVAL;

                }



                ret = bdrv_get_info(blk_bs(blk), &bdi);

                if (ret == 0 && bdi.cluster_size > 0 &&

                    bdi.cluster_size <= BLOCK_SIZE &&

                    BLOCK_SIZE % bdi.cluster_size == 0) {

                    cluster_size = bdi.cluster_size;

                } else {

                    cluster_size = BLOCK_SIZE;

                }

            }



            if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
@@ -932,10 +943,30 @@ static int block_load(QEMUFile *f, void *opaque, int version_id) 
                                        nr_sectors * BDRV_SECTOR_SIZE,

                                        BDRV_REQ_MAY_UNMAP);

            } else {

                int i;

                int64_t cur_addr;

                uint8_t *cur_buf;



                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);

                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 ((!block_mig_state.zero_blocks ||

                        cluster_size < BLOCK_SIZE) &&

                        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);

                    }

                    if (ret < 0) {

                        break;

                    }

                }

                g_free(buf);

            }