[PATCH v3 0/5] Implement reflink support

[Fabian Maurer]

Hello,

first, thanks for working on this, would be a welcome improvement!
Do I understand that right that it wouldn't work for ext4 and there's not
really anything we could do to support it?

Regards,
Fabian Maurer

On Donnerstag, 27. Januar 2022 22:50:51 CET Alex Xu (Hello71) wrote:
> Over the years, Wine prefixes have gotten bigger and bigger, for a
> number of reasons. Creating a new Wine prefix for each application is
> still the current recommendation, as despite the best efforts of Wine
> developers, some applications still require system-wide workarounds.
> This leads to significant bloat for each application installed. With a
> MinGW build of Wine without Mono or Gecko, new 32-bit prefixes are over
> 150 MB, and new 64-bit prefixes are over 300 MB. The vast majority of
> these files are byte-for-byte identical to Wine's central DLL copies.
>
> This patch set implements reflink support in Wine via the
> copy_file_range syscall. The reasons for selecting copy_file_range over
> FICLONE are outlined in patch 2. A previous unpublished version of this
> patch set used FICLONERANGE, but it was less convenient to use from
> setupapi and has inferior system support.
>
> When reflink is supported by the underlying filesystem, new Wine prefix
> sizes with Mono and Gecko disabled are reduced to less than 1 MB. The
> resulting Wine prefix is byte-for-byte identical to one created without
> reflink, but occupies less space on disk. If hard links or symlinks were
> used, if an application such as winetricks writes to a system file, it
> would overwrite the central copy. With reflink, the file blocks will be
> transparently copied by the Linux kernel so that each Wine prefix can be
> independent.
>
> Some files cannot be deduplicated in the current Wine system, as they
> are dynamically generated during the Wine prefix installation process.
> These include 16-bit fake DLLs and manifest files. In theory, it should
> be possible to pre-generate these files, but considering the Wine prefix
> size is already reduced to less than 1 MB, the extra space savings are
> likely not worth the effort.
>
> v1->v2: Fix/improve errno handling.
> v2->v3: Rebase.
>
> Alex Xu (Hello71) (5):
>   ntdll: add support for IOCTL_COPYCHUNK.
>   kernelbase: use IOCTL_COPYCHUNK in CopyFile*
>   setupapi: Use IOCTL_COPYCHUNK, avoid buffering whole file
>   lmshare.h: define STYPE_TEMPORARY
>   kernel32/tests: add IOCTL_COPYCHUNK test
>
>  configure                  |   6 ++
>  configure.ac               |   1 +
>  dlls/kernel32/tests/file.c | 137 +++++++++++++++++++++++++
>  dlls/kernelbase/file.c     |  44 ++++-----
>  dlls/ntdll/unix/file.c     | 121 +++++++++++++++++++++++
>  dlls/setupapi/fakedll.c    | 198 ++++++++++++++++++++-----------------
>  include/config.h.in        |   3 +
>  include/lmshare.h          |  11 ++-
>  include/winioctl.h         |  34 +++++++
>  9 files changed, 434 insertions(+), 121 deletions(-)