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Re: [Qemu-block] [PATCH 2/2] migration/block: use blk_pwrite_zeroes for
From: |
Fam Zheng |
Subject: |
Re: [Qemu-block] [PATCH 2/2] migration/block: use blk_pwrite_zeroes for each zero cluster |
Date: |
Fri, 7 Apr 2017 15:08:41 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Thu, 04/06 21:15, address@hidden wrote:
> From: Lidong Chen <address@hidden>
>
> 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 <address@hidden>
> ---
> migration/block.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/migration/block.c b/migration/block.c
> index 7734ff7..1fce9b9 100644
> --- a/migration/block.c
> +++ b/migration/block.c
> @@ -885,6 +885,10 @@ static int block_load(QEMUFile *f, void *opaque, int
> version_id)
> int64_t total_sectors = 0;
> int nr_sectors;
> int ret;
> + int i;
> + int cluster_size;
> + int64_t addr_offset;
> + uint8_t *buf_offset;
>
> do {
> addr = qemu_get_be64(f);
> @@ -934,8 +938,34 @@ 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);
> +
> + cluster_size = bdrv_get_cluster_size(blk_bs(blk));
> +
> + if (cluster_size > 0) {
> + for (i = 0; i < BLOCK_SIZE / cluster_size; i++) {
Should we check that cluster_size < BLOCK_SIZE and (BLOCK_SIZE % cluster_size ==
0)?
Fam
> + addr_offset = addr * BDRV_SECTOR_SIZE
> + + i * cluster_size;
> + buf_offset = buf + i * cluster_size;
> +
> + if (buffer_is_zero(buf_offset, cluster_size)) {
> + ret = blk_pwrite_zeroes(blk, addr_offset,
> + cluster_size,
> + BDRV_REQ_MAY_UNMAP);
> + } else {
> + ret = blk_pwrite(blk, addr_offset,
> + buf_offset, cluster_size, 0);
> + }
> +
> + 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
>