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migration/block: use blk_pwrite_zeroes for each zero cluster

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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: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Lidong Chen <lidongchen@tencent.com>
Message-id: 1492050868-16200-1-git-send-email-lidongchen@tencent.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Lidong Chen 2017-04-13 10:34:28 +08:00 committed by Stefan Hajnoczi
parent d72915c60b
commit 3928d50bf1
1 changed files with 33 additions and 2 deletions
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35
migration/block.c
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@ -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);
}