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Re: [Qemu-block] [PATCH 1/4] qcow2: Avoid COW during metadata preallocat
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From: |
Eric Blake |
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Subject: |
Re: [Qemu-block] [PATCH 1/4] qcow2: Avoid COW during metadata preallocation |
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Date: |
Mon, 15 Apr 2019 11:14:08 -0500 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 4/15/19 10:54 AM, Kevin Wolf wrote:
> Limiting the allocation to INT_MAX bytes isn't particularly clever
> because it means that the final cluster will be a partial cluster which
> will be completed through a COW operation. This results in unnecessary
> data read and write requests which lead to an unwanted non-sparse
> filesystem block for metadata preallocation.
>
> Align the maximum allocation size down to the cluster size to avoid this
> situation.
>
> Cc: address@hidden
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block/qcow2.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
Reviewed-by: Eric Blake <address@hidden>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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- [Qemu-block] [PATCH 0/4] qcow2: Preallocation fixes, Kevin Wolf, 2019/04/15
- [Qemu-block] [PATCH 1/4] qcow2: Avoid COW during metadata preallocation, Kevin Wolf, 2019/04/15
- Re: [Qemu-block] [PATCH 1/4] qcow2: Avoid COW during metadata preallocation,
Eric Blake <=
- [Qemu-block] [PATCH for-4.0? 2/4] qcow2: Fix preallocation bdrv_pwrite to wrong file, Kevin Wolf, 2019/04/15
- [Qemu-block] [PATCH 4/4] qcow2: Fix full preallocation with external data file, Kevin Wolf, 2019/04/15
- [Qemu-block] [PATCH 3/4] qcow2: Add errp to preallocate_co(), Kevin Wolf, 2019/04/15
- Re: [Qemu-block] [PATCH 0/4] qcow2: Preallocation fixes, Kevin Wolf, 2019/04/29