Gentoo Archives: gentoo-dev

From: "Michał Górny" <mgorny@g.o>
To: gentoo-dev@l.g.o
Cc: nirbheek@g.o, rich0@g.o
Subject: Re: [gentoo-dev] Re: proj/portage:master commit in: pym/portage/dbapi/
Date: Sat, 26 Nov 2011 16:10:21
Message-Id: 20111126170831.16d9d656@pomiocik.lan
In Reply to: Re: [gentoo-dev] Re: proj/portage:master commit in: pym/portage/dbapi/ by Nirbheek Chauhan
On Sat, 26 Nov 2011 21:28:51 +0530
Nirbheek Chauhan <nirbheek@g.o> wrote:

> On Sat, Nov 26, 2011 at 8:39 PM, Michał Górny <mgorny@g.o> > 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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Re: [gentoo-dev] Re: proj/portage:master commit in: pym/portage/dbapi/ Nirbheek Chauhan <nirbheek@g.o>