Re: [RFC PATCH v2 16/26] qcow2: Add subcluster support to discard_in_l2_slice()

[Max Reitz]

On 26.10.19 23:25, Alberto Garcia wrote:
> Setting the QCOW_OFLAG_ZERO bit of the L2 entry is forbidden if an
> image has subclusters. Instead, the individual 'all zeroes' bits must
> be used.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block/qcow2-cluster.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 3e4ba8d448..aa3eb727a5 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -1772,7 +1772,11 @@ static int discard_in_l2_slice(BlockDriverState *bs, 
> uint64_t offset,
>  
>          /* First remove L2 entries */
>          qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
> -        if (!full_discard && s->qcow_version >= 3) {
> +        if (has_subclusters(s)) {
> +            set_l2_entry(s, l2_slice, l2_index + i, 0);
> +            set_l2_bitmap(s, l2_slice, l2_index + i,
> +                          full_discard ? 0 : QCOW_L2_BITMAP_ALL_ZEROES);

But only for !full_discard, right?

Max

> +        } else if (!full_discard && s->qcow_version >= 3) {
>              set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO);
>          } else {
>              set_l2_entry(s, l2_slice, l2_index + i, 0);
>

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