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

[Gonglei <arei.gonglei@huawei.com>]

Hi,

You should change your patch's commit message to show what your patch solved.

Please refer to the guide:
 http://wiki.qemu.org/Contribute/SubmitAPatch

Regards,
-Gonglei

On 2016/9/2 14:41, zhangzhiming wrote:
> ping
> 
> zhangzhiming
> zhangzhiming02@meituan.com
> 
> 
> 
>> On Aug 15, 2016, at 7:56 PM, zhangzhiming <zhangzhiming02@meituan.com> wrote:
>>
>> hi, i modified my code by Kevin Wolf’s review. and thanks for review again.
>>
>>
>>
>> Signed-off-by: zhangzhiming <zhangzhiming02@meituan.com>
>> ---
>> 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
>> zhangzhiming02@meituan.com
>>
>>
>>
> 
> 
> 
> .
>