Giuseppe Scrivano wrote:
> Jim Meyering <j...@meyering.net> writes:
>
>>>> Adding this optimization should not change the meaning of
>>>> --sparse=always.
>>>
>>> So do you want to use it only when --sparse=auto is used?
>>
>> Precisely.
>
> I cleaned the patch a bit, the clone operation is done only when
> --sparse=auto is used.
Thanks.
Here's an adjusted version that moves the in-function #ifdefs into
a helper function and includes sys/ioctl.h whenever HAVE_SYS_IOCTL_H
is defined. I'll adjust indentation in a separate patch.
>From 2be19afe6a06bdf4172ab10ff657a32121960217 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscriv...@gnu.org>
Date: Sat, 25 Jul 2009 16:35:27 +0200
Subject: [PATCH] cp: support btrfs' copy-on-write file clone operation
* src/copy.c [HAVE_SYS_IOCTL_H]: Include <sys/ioctl.h>.
(clone_file): New function.
(copy_reg): Use the btrfs clone operation if possible.
---
src/copy.c | 27 +++++++++++++++++++++++++++
1 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/src/copy.c b/src/copy.c
index 4c8c432..34af802 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -61,6 +61,10 @@
# include "verror.h"
#endif
+#if HAVE_SYS_IOCTL_H
+# include <sys/ioctl.h>
+#endif
+
#ifndef HAVE_FCHOWN
# define HAVE_FCHOWN false
# define fchown(fd, uid, gid) (-1)
@@ -114,6 +118,20 @@ static bool owner_failure_ok (struct cp_options const *x);
static char const *top_level_src_name;
static char const *top_level_dst_name;
+/* Perform the O(1) btrfs clone operation, if possible.
+ Upon success, return 0. Otherwise, return -1 and set errno. */
+static inline int
+clone_file (int dest_fd, int src_fd)
+{
+#ifdef __linux__
+# define BTRFS_IOC_CLONE 1074041865
+ return ioctl (dest_fd, BTRFS_IOC_CLONE, src_fd);
+#else
+ errno = ENOTSUP;
+ return -1;
+#endif
+}
+
/* FIXME: describe */
/* FIXME: rewrite this to use a hash table so we avoid the quadratic
performance hit that's probably noticeable only on trees deeper
@@ -444,6 +462,7 @@ copy_reg (char const *src_name, char const *dst_name,
struct stat sb;
struct stat src_open_sb;
bool return_val = true;
+ bool copied = false;
source_desc = open (src_name,
(O_RDONLY | O_BINARY
@@ -589,6 +608,14 @@ copy_reg (char const *src_name, char const *dst_name,
goto close_src_and_dst_desc;
}
+ /* If --sparse=auto is in effect, attempt a btrfs clone operation.
+ If the operation is not supported or it fails then copy the file
+ in the usual way. */
+ if (x->sparse_mode == SPARSE_AUTO
+ && clone_file (dest_desc, source_desc) == 0)
+ copied = true;
+
+ if (!copied)
{
typedef uintptr_t word;
off_t n_read_total = 0;
--
1.6.4.rc3.195.g2b05
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