Re: cpio copy-out reflink and chain support

[Luis Henriques]

On Fri, Mar 12, 2021 at 02:30:11AM +0100, David Disseldorp wrote:
> This patchset adds support for Linux copy_file_range() syscall usage via
> a new '--reflink' copy-out parameter. The syscall can considerably
> improve archive creation performance and space efficiency on
> copy-on-write filesystems such as XFS and Btrfs by performing a metadata
> only reflink instead of regular read/write copy I/O. The patchset is
> built on Luis' previous submission at:
> https://lists.gnu.org/archive/html/bug-cpio/2020-07/msg00001.html
> 
> An additional '--chain' parameter is also added for appending a new
> archive to an existing file. This is useful for Linux initramfs images,
> which can be chained back-to-back.
> Unit test coverage for both new parameters is provided.
> 
> Dracut changes to make use of the above features when building a Linux
> initramfs image have been submitted upstream via:
> https://github.com/dracutdevs/dracut/pull/1148 .
> 
> This patch set also carries the queued change at
> https://savannah.gnu.org/patch/?9263 .
> 
> Feedback appreciated.

First of all, thanks a lot for picking this and making the full work do
something useful.  At least dracut could benefit a *lot* from this.

I've gone through the patches and, although I didn't do an exhaustive
testing, things look pretty good to me.  I've just a few comments in 2
patches, following soon.

Cheers,
--
Luís

> 
> Cheers, David
> 
> --
> 
>  configure.ac       |  6 +++
>  src/copyin.c       |  2 +-
>  src/copyout.c      | 43 +++++++++++++++++---
>  src/extern.h       |  7 +++-
>  src/global.c       |  7 +++-
>  src/main.c         | 50 +++++++++++++++++++++--
>  src/mt.c           |  4 +-
>  src/util.c         | 65 ++++++++++++++++++++++++++++--
>  tests/chain.at     | 91 ++++++++++++++++++++++++++++++++++++++++++
>  tests/reflink.at   | 98 ++++++++++++++++++++++++++++++++++++++++++++++
>  tests/testsuite.at |  2 +
>  11 files changed, 356 insertions(+), 19 deletions(-)
>