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Re: [Qemu-devel] [PATCH] qcow2: Simplify calculation for COW area at the
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] qcow2: Simplify calculation for COW area at the end |
Date: |
Tue, 12 Jun 2012 16:00:45 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 |
Il 12/06/2012 15:47, Kevin Wolf ha scritto:
> copy_sectors() always uses the sum (cluster_offset + n_start) or
> (start_sect + n_start), so if some value is added to both cluster_offset
> and start_sect, and subtracted from n_start, it's cancelled out anyway.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block/qcow2-cluster.c | 5 ++---
> 1 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index 9aee9fc..763b724 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -640,11 +640,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs,
> QCowL2Meta *m)
> }
>
> if (m->nb_available & (s->cluster_sectors - 1)) {
> - uint64_t end = m->nb_available & ~(uint64_t)(s->cluster_sectors - 1);
> cow = true;
> qemu_co_mutex_unlock(&s->lock);
> - ret = copy_sectors(bs, start_sect + end, cluster_offset + (end << 9),
> - m->nb_available - end, s->cluster_sectors);
> + ret = copy_sectors(bs, start_sect, cluster_offset,
> + m->nb_available, s->cluster_sectors);
Do you need to add end to s->cluster_sectors too, so that "start_sect +
n_end" and "n_end - n_start" remain the same?
Paolo