[libvirt] [PATCHv2 12/16] save: add virFileDirectFd wrapper type
Daniel P. Berrange
berrange at redhat.com
Thu Jul 21 11:33:38 UTC 2011
On Tue, Jul 19, 2011 at 10:20:35PM -0600, Eric Blake wrote:
> O_DIRECT has stringent requirements. Rather than make lots of changes
> at each site that wants to use O_DIRECT, it is easier to offload
> the work through a helper process that mirrors the I/O between a
> pipe and the actual direct fd, so that the other end of the pipe
> no longer has to worry about constraints.
>
> Plus, if the kernel ever gains better posix_fadvise support, then we
> only have to touch a single file to let all callers benefit from a
> more efficient way to avoid file system caching.
>
> * src/util/virfile.h (virFileDirectFdFlag, virFileDirectFdNew)
> (virFileDirectFdClose, virFileDirectFdFree): New prototypes.
> * src/util/virdirect.c: Implement new wrapper object.
> * src/libvirt_private.syms (virfile.h): Export new symbols.
> * cfg.mk (useless_free_options): Add to list.
> * po/POTFILES.in: Add new translations.
> ---
>
> v2: move everything into virfile.c rather than creating a new file,
> with renames everywhere. Fail rather than silently ignore systems
> where O_DIRECT is 0. Add comments to take advantage of posix_fadvise
> rather than O_DIRECT if the Linux kernel ever gets fixed. Add
> virFileDirectFdFlag as a better probe of which cache-bypass mechanism
> is actually being used. Better documentation.
>
> cfg.mk | 1 +
> po/POTFILES.in | 1 +
> src/libvirt_private.syms | 4 +
> src/util/virfile.c | 175 +++++++++++++++++++++++++++++++++++++++++++++-
> src/util/virfile.h | 15 ++++
> 5 files changed, 195 insertions(+), 1 deletions(-)
ACK
Daniel
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