Re: BTRFS file clone support for cp

[Giuseppe Scrivano]

Jim Meyering <address@hidden> 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.

Regards,
Giuseppe


>From 747c96980acc25220cc436210403cdcaed6239c9 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Sat, 25 Jul 2009 16:35:27 +0200
Subject: [PATCH] cp: support the btrfs file system clone operation.

* src/copy.c(copy_reg): Use the btrfs clone operation if it is possible.
---
 src/copy.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/src/copy.c b/src/copy.c
index 4c8c432..e0ddec5 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -61,6 +61,11 @@
 # include "verror.h"
 #endif
 
+#ifdef __linux__
+# include <sys/ioctl.h>
+# define BTRFS_IOC_CLONE 1074041865
+#endif
+
 #ifndef HAVE_FCHOWN
 # define HAVE_FCHOWN false
 # define fchown(fd, uid, gid) (-1)
@@ -444,6 +449,7 @@ 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 +595,15 @@ copy_reg (char const *src_name, char const *dst_name,
       goto close_src_and_dst_desc;
     }
 
+#ifdef __linux__
+  /* Try 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) && !ioctl (dest_desc, BTRFS_IOC_CLONE,
+                                                 source_desc))
+    copied = true;
+#endif
+
+  if (!copied)
   {
     typedef uintptr_t word;
     off_t n_read_total = 0;
-- 
1.6.3.3