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Re: [Qemu-block] [PATCH v3 27/39] qcow2: Update qcow2_update_snapshot_re


From: Max Reitz
Subject: Re: [Qemu-block] [PATCH v3 27/39] qcow2: Update qcow2_update_snapshot_refcount() to support L2 slices
Date: Thu, 1 Feb 2018 20:26:26 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2

On 2018-01-26 15:59, Alberto Garcia wrote:
> qcow2_update_snapshot_refcount() increases the refcount of all
> clusters of a given snapshot. In order to do that it needs to load all
> its L2 tables and iterate over their entries. Since we'll be loading
> L2 slices instead of full tables we need to add an extra loop that
> iterates over all slices of each L2 table.
> 
> This function doesn't need any additional changes so apart from that
> this patch simply updates the variable name from l2_table to l2_slice.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block/qcow2-refcount.c | 31 +++++++++++++++++--------------
>  1 file changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
> index dfa28301c4..60b521cb89 100644
> --- a/block/qcow2-refcount.c
> +++ b/block/qcow2-refcount.c
> @@ -1183,17 +1183,20 @@ int qcow2_update_snapshot_refcount(BlockDriverState 
> *bs,
>      int64_t l1_table_offset, int l1_size, int addend)
>  {
>      BDRVQcow2State *s = bs->opaque;
> -    uint64_t *l1_table, *l2_table, l2_offset, entry, l1_size2, refcount;
> +    uint64_t *l1_table, *l2_slice, l2_offset, entry, l1_size2, refcount;
>      bool l1_allocated = false;
>      int64_t old_entry, old_l2_offset;
> +    unsigned slice, slice_size2, n_slices;

Hm, well. Hm.

>      int i, j, l1_modified = 0, nb_csectors;
>      int ret;
>  
>      assert(addend >= -1 && addend <= 1);
>  
> -    l2_table = NULL;
> +    l2_slice = NULL;
>      l1_table = NULL;
>      l1_size2 = l1_size * sizeof(uint64_t);
> +    slice_size2 = s->l2_slice_size * sizeof(uint64_t);
> +    n_slices = s->cluster_size / slice_size2;
>  
>      s->cache_discards = true;
>  

[...]

> @@ -1273,12 +1276,13 @@ int qcow2_update_snapshot_refcount(BlockDriverState 
> *bs,
>                      case QCOW2_CLUSTER_NORMAL:
>                      case QCOW2_CLUSTER_ZERO_ALLOC:
>                          if (offset_into_cluster(s, offset)) {
> +                            int l2_index = slice * s->l2_slice_size + j;
>                              qcow2_signal_corruption(
>                                  bs, true, -1, -1, "Cluster "
>                                  "allocation offset %#" PRIx64
>                                  " unaligned (L2 offset: %#"
>                                  PRIx64 ", L2 index: %#x)",
> -                                offset, l2_offset, j);
> +                                offset, l2_offset, l2_index);

This makes it a bit weird that in other patches l2_index is now
generally the L2 slice index...

Oh well.

Reviewed-by: Max Reitz <address@hidden>

>                              ret = -EIO;
>                              goto fail;
>                          }

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