[libvirt] [PATCH 1/2] Introduce btrfsCloneFile for btrfs COW copy

[Chen, Hanxiao]

> -----Original Message-----
> From: Ján Tomko [mailto:jtomko at redhat.com]
> Sent: Friday, January 16, 2015 10:21 PM
> To: Chen, Hanxiao/陈 晗霄; libvir-list at redhat.com
> Subject: Re: [libvirt] [PATCH 1/2] Introduce btrfsCloneFile for btrfs COW copy
> 
> On 01/13/2015 09:18 AM, Chen Hanxiao wrote:
> > Signed-off-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>
> > ---
> >  src/storage/storage_backend.c | 26 ++++++++++++++++++++++++++
> >  1 file changed, 26 insertions(+)
> >
> > diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
> > index b990a82..5ce3566 100644
> > --- a/src/storage/storage_backend.c
> > +++ b/src/storage/storage_backend.c
> > @@ -156,6 +156,32 @@ enum {
> >  #define READ_BLOCK_SIZE_DEFAULT  (1024 * 1024)
> >  #define WRITE_BLOCK_SIZE_DEFAULT (4 * 1024)
> >
> > +/*
> > + * Perform the O(1) btrfs clone operation, if possible.
> > + * Upon success, return 0.  Otherwise, return -1 and set errno.
> > + */
> > +#if !defined(BTRFS_IOCTL_MAGIC)
> > +# define BTRFS_IOCTL_MAGIC 0x94
> > +#endif
> > +
> > +#define BTRFS_IOC_CLONE _IOW (BTRFS_IOCTL_MAGIC, 9, int)
> > +
> 
> Instead of redefining the constants, can we check for btrfs.h at configure
> time and wrap the function in #ifdef BTRFS_IOC_CLONE ?
> 
We need to install btrfs-progs-devel for BTRFS_IOC_CLONE in <btrfs/ioctl.h>.
So it should be easy to just define magic number and issue a ioctl,
than add a dependency on btrfs-progs-devel.

Do we need to add a LIBVIRT_CHECK_PKG for btrfs-progs-devel?

Thanks,
- Chen