Re: [Qemu-devel] [PATCH v5 23/42] blockdev: Use CAF in external_snapshot_prepare()

[Max Reitz]

On 14.06.19 17:46, Vladimir Sementsov-Ogievskiy wrote:
> 13.06.2019 1:09, Max Reitz wrote:
>> This allows us to differentiate between filters and nodes with COW
>> backing files: Filters cannot be used as overlays at all (for this
>> function).
>>
>> Signed-off-by: Max Reitz <address@hidden>
> 
> Overlay created in snapshot operation assumed to consume following writes
> and it's filtered child becomes readonly.. And filter works in completely 
> another
> way.
> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> 
> [hmm, I start to like using "filtered child" collocation when I say about 
> this thing.
>   didn't you think about renaming backing chain to filtered chain?]

Hm.  There are backing chains and there are backing chains.  There are
qemu-internal backing chains that consist of a healthy mix of filters
and COW overlays, and then there are the more high-level backing chains
the user actually manages, where only the overlays are important.

I think it would make sense to rename the “qemu-internal backing chains"
to “filter chains” or something.  But that makes it sound a bit like it
would only mean R/W filters...  Maybe just “chain”?

Actually, the only functions I find are is_backing_chain_frozen & Co,
and they could simply become is_chain_frozen.  Is there anything else?

Max

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