hooanon05@xxxxxxxxxxx writes:
> Goswin von Brederlow:
>> For unlink and rmdir you need whiteout files.
>>
>> For all the rest you just have to keep the file descriptor(s) alive as
>> long as the file is opened and cache metadat in the internal FD
>> structure.
>>
>> It isn't trivial but it isn't really hard.
>
> Generally it is true.
> Actually deltafs already has something like whiteout. It is a symlink to
> "(null)".
> When a user writes something to the file after unlink+rmdir, where can
> deltafs copyup? At least in the current implementation, there is no
> place for it.
>
>
> J. R. Okajima
In the delta branch create a meta/ and files/ directory. In the meta/
directory you keep whiteout files and stat updates. In files/ you
store only changes in the file data itself.
So "rm foo/bar/baz" will create meta/foo/bar/baz.whiteout. Then "echo
blafase >>foo/bar/baz" first searches for a file to copy-up, sees the
meta/foo/bar/baz.whiteout and knows the file was deleted. It then
creates a new files/foo/bar/baz. It might have to copy-up foo and
foo/bar for that though.
MfG
Goswin
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