Re: [Qemu-block] Subject: [PATCH] qcow2 resize with snapshot, mod

[zhangzhiming]

ping

zhangzhiming
address@hidden



> On Aug 15, 2016, at 7:56 PM, zhangzhiming <address@hidden> wrote:
> 
> hi, i modified my code by Kevin Wolf’s review. and thanks for review again.
> 
> 
> 
> Signed-off-by: zhangzhiming <address@hidden>
> ---
> block.c                |   19 ----------------
> block/qcow2-cluster.c  |   55 ++++++++++++++++++++++++++++++++++--------------
> block/qcow2-snapshot.c |   34 ++++++++++++++--------------
> block/qcow2.c          |    2 +-
> block/qcow2.h          |    2 +-
> 5 files changed, 58 insertions(+), 54 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 0de7b2d..f54bc25 100644
> --- a/block.c
> +++ b/block.c
> @@ -2586,25 +2586,6 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset)
>     return ret;
> }
> 
> -int bdrv_apply_snapshot(BlockDriverState *bs, const char *snapshot_id,
> -                        uint64_t snapshot_size)
> -{
> -    int ret = bdrv_snapshot_goto(bs, snapshot_id);
> -    if (ret < 0) {
> -        return ret;
> -    }
> -
> -    ret = refresh_total_sectors(bs, snapshot_size >> BDRV_SECTOR_BITS);
> -    if (ret < 0) {
> -        return ret;
> -    }
> -    bdrv_dirty_bitmap_truncate(bs);
> -    if (bs->blk) {
> -        blk_dev_resize_cb(bs->blk);
> -    }
> -    return ret;
> -}
> -
> /**
>  * Length of a allocated file in bytes. Sparse files are counted by actual
>  * allocated space. Return < 0 if error or unknown.
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index ebadddf..2190528 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -32,32 +32,55 @@
> #include "qemu/bswap.h"
> #include "trace.h"
> 
> -int shrink_l1_table(BlockDriverState *bs, int64_t new_l1_size)
> +static int free_some_l2_table(BlockDriverState *bs, int64_t old_size,
> +                              int64_t new_size)
> {
>     BDRVQcow2State *s = bs->opaque;
> -    int64_t old_l1_size = s->l1_size;
> -    s->l1_size = new_l1_size;
> -    int ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
> -                                             s->l1_size, 1);
> -    if (ret < 0) {
> -        return ret;
> +    int old_l1_size = size_to_l1(s, old_size);
> +    int new_l1_size = size_to_l1(s, new_size);
> +    if (old_l1_size == new_l1_size) {
> +        return 0;
>     }
> +    int i;
> +    for (i = new_l1_size; i < old_l1_size; i++) {
> +        uint64_t l2_offset = s->l1_table[i] & L1E_OFFSET_MASK;
> +        qcow2_free_clusters(bs, l2_offset, s->cluster_size,
> +                            QCOW2_DISCARD_OTHER);
> +        s->l1_table[i] = 0;
> +        /* write l1 entry will be called for several times and
> +         * because l1 is short, i think is tolerated! */
> +        qcow2_write_l1_entry(bs, i);
> +    }
> +    return 0;
> +}
> 
> -    s->l1_size = old_l1_size;
> -    ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
> -                                         s->l1_size, -1);
> +int shrink_disk(BlockDriverState *bs, int64_t new_size)
> +{
> +    BDRVQcow2State *s = bs->opaque;
> +    int64_t old_size = bs->total_sectors * 512;
> +    int64_t new_sector_nb = DIV_ROUND_UP(new_size, 512);
> +    int64_t discard_sectors_nb = bs->total_sectors - new_sector_nb;
> +    int64_t old_cluster_nb = DIV_ROUND_UP(old_size, s->cluster_size);
> +    int64_t new_cluster_nb = DIV_ROUND_UP(new_size, s->cluster_size);
> +    if (old_cluster_nb == new_cluster_nb) {
> +        return 0;
> +    }
> +    s->l1_size = size_to_l1(s, new_size);
> +    bs->total_sectors = new_sector_nb;
> +    int ret = qcow2_update_header(bs);
>     if (ret < 0) {
> +        s->l1_size = size_to_l1(s, old_size);
> +        bs->total_sectors = old_size / 512;
>         return ret;
>     }
> -    s->l1_size = new_l1_size;
> 
> -    uint32_t be_l1_size = cpu_to_be32(s->l1_size);
> -    ret = bdrv_pwrite_sync(bs->file->bs, offsetof(QCowHeader, l1_size),
> -                           &be_l1_size, sizeof(be_l1_size));
> +    /* can't be undone here, if failed nothing will be done */
> +    ret = qcow2_discard_clusters(bs, new_size, discard_sectors_nb,
> +                                 QCOW2_DISCARD_OTHER, true);
>     if (ret < 0) {
> -        return ret;
> +        return 0;
>     }
> -
> +    free_some_l2_table(bs, old_size, new_size);
>     return 0;
> }
> 
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index 6dd6769..40a0d26 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -490,6 +490,7 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char 
> *snapshot_id)
> 
>     cur_l1_bytes = s->l1_size * sizeof(uint64_t);
>     sn_l1_bytes = sn->l1_size * sizeof(uint64_t);
> +    int max_l1_size_bytes = MAX(sn_l1_bytes, cur_l1_bytes);
> 
>     /*
>      * Copy the snapshot L1 table to the current L1 table.
> @@ -499,7 +500,7 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char 
> *snapshot_id)
>      * Decrease the refcount referenced by the old one only when the L1
>      * table is overwritten.
>      */
> -    sn_l1_table = g_try_malloc0(sn_l1_bytes);
> +    sn_l1_table = g_try_malloc0(max_l1_size_bytes);
>     if (sn_l1_bytes && sn_l1_table == NULL) {
>         ret = -ENOMEM;
>         goto fail;
> @@ -517,34 +518,32 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const 
> char *snapshot_id)
>         goto fail;
>     }
> 
> -    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
> -                                        s->l1_table_offset, sn_l1_bytes);
> -    if (ret < 0) {
> -        goto fail;
> -    }
> -
> -    ret = bdrv_pwrite_sync(bs->file->bs, s->l1_table_offset, sn_l1_table,
> -                           sn_l1_bytes);
> +    /* update meta data first, for failed */
> +    int old_l1_size = s->l1_size;
> +    uint64_t old_total_sectors = bs->total_sectors;
> +    bs->total_sectors = sn->disk_size / BDRV_SECTOR_SIZE;
> +    s->l1_size = sn->l1_size;
> +    ret = qcow2_update_header(bs);
>     if (ret < 0) {
> +        s->l1_size = old_l1_size;
> +        bs->total_sectors = old_total_sectors;
>         goto fail;
>     }
> 
> -    /* write updated header.size */
> -    uint64_t be_disk_size = cpu_to_be64(sn->disk_size);
> -    ret = bdrv_pwrite_sync(bs->file->bs, offsetof(QCowHeader, size),
> -                           &be_disk_size, sizeof(uint64_t));
> +    /* and then update l1 table */
> +    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
> +                                        s->l1_table_offset, 
> max_l1_size_bytes);
>     if (ret < 0) {
>         goto fail;
>     }
> 
> -    uint32_t be_l1_size = cpu_to_be32(sn->l1_size);
> -    ret = bdrv_pwrite_sync(bs->file->bs, offsetof(QCowHeader, l1_size),
> -                           &be_l1_size, sizeof(be_l1_size));
> +    ret = bdrv_pwrite_sync(bs->file->bs, s->l1_table_offset, sn_l1_table,
> +                           max_l1_size_bytes);
>     if (ret < 0) {
>         goto fail;
>     }
> 
> -    s->l1_vm_state_index = sn->l1_size;
> +    s->l1_vm_state_index = size_to_l1(s, sn->disk_size);;
> 
>     /*
>      * Decrease refcount of clusters of current L1 table.
> @@ -556,6 +555,7 @@ int qcow2_snapshot_goto(BlockDriverState *bs, const char 
> *snapshot_id)
>      * the in-memory data instead of really using the offset to load a new 
> one,
>      * which is why this works.
>      */
> +    s->l1_size = old_l1_size;
>     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
>                                          s->l1_size, -1);
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 612a534..01a66f2 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2513,7 +2513,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t 
> offset)
> 
>     new_l1_size = size_to_l1(s, offset);
>     if (offset < bs->total_sectors * 512) {
> -        ret = shrink_l1_table(bs, new_l1_size);
> +        ret = shrink_disk(bs, offset);
>         if (ret < 0) {
>             return ret;
>         }
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 8efa735..ba622b6 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -534,7 +534,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int 
> refcount_order,
>                                 void *cb_opaque, Error **errp);
> 
> /* qcow2-cluster.c functions */
> -int shrink_l1_table(BlockDriverState *bs, int64_t new_l1_size);
> +int shrink_disk(BlockDriverState *bs, int64_t new_size);
> int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
>                         bool exact_size);
> int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index);
> -- 
> 1.7.1
> 
> 
> 
> 
> zhangzhiming
> address@hidden
> 
> 
>