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Re: [Qemu-devel] [PATCH 4/8] block/backup: improve unallocated clusters
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From: |
Max Reitz |
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Subject: |
Re: [Qemu-devel] [PATCH 4/8] block/backup: improve unallocated clusters skipping |
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Date: |
Fri, 9 Aug 2019 14:25:43 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 09.08.19 09:50, Vladimir Sementsov-Ogievskiy wrote:
> 07.08.2019 21:01, Max Reitz wrote:
>> On 07.08.19 10:07, Vladimir Sementsov-Ogievskiy wrote:
>>> Limit block_status querying to request bounds on write notifier to
>>> avoid extra seeking.
>>
>> I don’t understand this reasoning. Checking whether something is
>> allocated for qcow2 should just mean an L2 cache lookup. Which we have
>> to do anyway when we try to copy data off the source.
>
> But for raw it's seeking.
(1) That’s a bug in block_status then, isn’t it?
file-posix cannot determine the allocation status, or rather, everything
is allocated. bdrv_co_block_status() should probably pass @want_zero on
to the driver’s implementation, and file-posix should just
unconditionally return DATA if it’s false.
(2) Why would you even use sync=top for raw nodes?
Max
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[Qemu-devel] [PATCH 3/8] block/io: handle alignment and max_transfer for copy_range, Vladimir Sementsov-Ogievskiy, 2019/08/07
[Qemu-devel] [PATCH 7/8] block/backup: merge duplicated logic into backup_do_cow, Vladimir Sementsov-Ogievskiy, 2019/08/07
[Qemu-devel] [PATCH 6/8] block/backup: teach backup_cow_with_bounce_buffer to copy more at once, Vladimir Sementsov-Ogievskiy, 2019/08/07
[Qemu-devel] [PATCH 8/8] block/backup: backup_do_cow: use bdrv_dirty_bitmap_next_dirty_area, Vladimir Sementsov-Ogievskiy, 2019/08/07