On 11.02.20 16:41, Alberto Garcia wrote: > On Tue 04 Feb 2020 06:08:18 PM CET, Max Reitz wrote: >> + /* Child to COW from (backing child) */ >> + BDRV_CHILD_COW = (1 << 3), > > Without the comment in brackets I'm not sure that I would have > understood that this is meant for backing files.
I put it in brackets because bs->backing isn’t always such a child (for filters it isn’t). That’s also the reason why I prefer to stress the COW aspect. > This is the "child that contains the data that is not allocated in the > parent", or something like that, right? Hm, so I suppose the problem is that I didn’t describe in which event the COW is to occur. (I didn’t because we only have one kind of COW in the block layer, namely for backing chains.) So maybe “Child from which to read all data that isn’t allocated in the parent (backing child); such data may be copied to the parent by means of COW or COR”? (The problem I see with this description is that it is kind of a tautology, because “allocation” is in turn defined by differentiating between layers of a backing chain, i.e. this layer and that backing/COW child we’re talking about here.) Max
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