[libvirt] [PATCHv2 1/2] storage: introduce btrfsCloneFile() for COW copy

[Ján Tomko]

On 01/23/2015 11:22 AM, Chen Hanxiao wrote:
> Signed-off-by: Chen Hanxiao <chenhanxiao at cn.fujitsu.com>
> ---
>  configure.ac                  | 12 ++++++++++++
>  src/storage/storage_backend.c | 24 ++++++++++++++++++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/configure.ac b/configure.ac
> index f370475..2498389 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2175,6 +2175,18 @@ fi
>  AM_CONDITIONAL([WITH_HYPERV], [test "$with_hyperv" = "yes"])
>  
>  
> +dnl
> +dnl check for kernel headers required by btrfs ioctl
> +dnl
> +if test "$with_linux" = "yes"; then

> +    have_btrfs=no
> +    AC_CHECK_HEADER([linux/btrfs.h],[have_btrfs=yes])
> +    if test "${have_btrfs}" = yes; then
> +        AC_DEFINE([HAVE_BTRFS_IOC_CLONE], 1,
> +                  [whether have btrfs CoW clone ioctl])

This macro name is misleading (it does not check for clone, just for btrfs.h).

Doing just:
AC_CHECK_HEADERS([linux/btrfs.h])
will define HAVE_LINUX_BTRFS_H

> +    fi
> +fi
> +
>  dnl Allow perl/python overrides
>  AC_PATH_PROGS([PYTHON], [python2 python])
>  AC_PATH_PROG([PERL], [perl])
> diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
> index b990a82..d2a664b 100644
> --- a/src/storage/storage_backend.c
> +++ b/src/storage/storage_backend.c
> @@ -46,6 +46,10 @@
>  # include <selinux/selinux.h>
>  #endif
>  
> +#if HAVE_BTRFS_IOC_CLONE
> +# include <linux/btrfs.h>
> +#endif
> +
>  #include "datatypes.h"
>  #include "virerror.h"
>  #include "viralloc.h"
> @@ -156,6 +160,26 @@ 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(HAVE_BTRFS_IOC_CLONE)

#if HAVE_LINUX_BTRFS_H

> +static inline int
> +btrfsCloneFile(int dest_fd, int src_fd)
> +{
> +    return ioctl(dest_fd, BTRFS_IOC_CLONE, src_fd);
> +}
> +#else
> +static inline int
> +btrfsCloneFile(int dest_fd ATTRIBUTE_UNUSED,
> +               int src_fd ATTRIBUTE_UNUSED)
> +{
> +    errno = ENOTSUP;
> +    return -1;
> +}
> +#endif
> +
>  static int ATTRIBUTE_NONNULL(2)
>  virStorageBackendCopyToFD(virStorageVolDefPtr vol,
>                            virStorageVolDefPtr inputvol,
> 

ACK

I simplified the configure check and pushed the patch.

Jan

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20150127/5a27953a/attachment-0001.sig>