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

Signed-off-by: Chen Hanxiao <chenhanxiao(a)cn.fujitsu.com&gt; --- 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])

+ 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)

+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,