On Fri, 22 Nov 2013 21:26:16 +0000 (UTC) Duncan <1i5t5.duncan@xxxxxxx> wrote: > > During testing I found that the NOCOW flag prevents file cloning from > > working. cp --reflink fails with EINVAL when the source file has the > > NOCOW flag set. > > That would be expected, since disabling COW means the file will be > updated in-place, and if reflink-copying was allowed, changing the one > view in-place would by definition change the other view of the same file, > since it /is/ the same file data. However snapshotting a subvolume which has NOCOW files *is* allowed. I'm told data is then COW'ed only once, and only the areas that are changed after the snapshot has been made (or something along those lines). So since snapshotting+NOCOW can be combined and everything works automagically as expected, maybe reflink could be made to work as well? -- With respect, Roman
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