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

-----Original Message----- From: Ján Tomko [mailto:jtomko@redhat.com] Sent: Friday, January 16, 2015 10:21 PM To: Chen, Hanxiao/陈 晗霄; libvir-list(a)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(a)cn.fujitsu.com&gt; > --- > 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 ?