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Re: [Qemu-devel] [PATCH 3/6] qcow2: simplify logic in qcow2_co_write_zer
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 3/6] qcow2: simplify logic in qcow2_co_write_zeroes |
Date: |
Mon, 16 May 2016 10:28:18 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 05/14/2016 06:01 AM, Denis V. Lunev wrote:
> Unaligned request could occupy only one cluster. This is true since the
s/request could/requests will/
> previous commit. Simplify the code taking this considiration into
s/considiration/consideration/
> account.
>
> There are no other changes so far.
>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Kevin Wolf <address@hidden>
> ---
> block/qcow2.c | 23 +++++------------------
> 1 file changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 62febfc..9a54bbd 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2436,33 +2436,20 @@ static coroutine_fn int
> qcow2_co_write_zeroes(BlockDriverState *bs,
> int tail = (sector_num + nb_sectors) % s->cluster_sectors;
>
> if (head != 0 || tail != 0) {
> - int64_t cl_end = -1;
> + int64_t cl_start = sector_num - head;
>
> - sector_num -= head;
> - nb_sectors += head;
> + assert(cl_start + s->cluster_sectors >= sector_num + nb_sectors);
In other words, the caller is now buggy if it ever passes us an
unaligned request that crosses cluster boundaries (the only requests
that can cross boundaries will be aligned).
With the grammar fix in the commit message,
Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH 0/6] qcow2_co_write_zeroes and related improvements, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 1/6] qemu-io: enable tracing in qemu-io, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 2/6] block: split write_zeroes always, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 3/6] qcow2: simplify logic in qcow2_co_write_zeroes, Denis V. Lunev, 2016/05/14
- Re: [Qemu-devel] [PATCH 3/6] qcow2: simplify logic in qcow2_co_write_zeroes,
Eric Blake <=
- [Qemu-devel] [PATCH 6/6] qcow2: merge is_zero_cluster helpers into qcow2_co_write_zeroes, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 5/6] qcow2: fix condition in is_zero_cluster, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 4/6] qcow2: add tracepoints for qcow2_co_write_zeroes, Denis V. Lunev, 2016/05/14