On Sat, 26 Nov 2011 21:28:51 +0530 Nirbheek Chauhan <nirbh...@gentoo.org> wrote:
> On Sat, Nov 26, 2011 at 8:39 PM, Michał Górny <mgo...@gentoo.org> > wrote: > > But in this particular case, I don't think COW is particularly > > useful. If it works only on filesystem bounds, we could move the > > file directly anyway. > > > > There are still a few specific cases in which CoW would indeed be > useful. IIRC, reflinking of files works across btrfs *subvolumes*, and > such a copy would normally be detected as a cross-device move. For such a thing, shouldn't rename() work neat anyway? > Another use would be an patch-merge which makes use of *ranged > reflinks* to only CoW copy those parts of the file that were > changed[1]. rsync has support for this, but only while appending to > files (--append-verify --no-whole-file). So, it'd be like: 1) CoW-dup old file, 2) patch-merge into the duped old file, 3) replace. Am I understanding correctly? -- Best regards, Michał Górny
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