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Re: [libvirt] [PATCHv2 12/16] save: add virFileDirectFd wrapper type



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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