[PATCH] Btrfs-progs/receive: sparse and pre-allocated file support, for btrfs-send mechanism

[Chen Yang <chenyang.fnst@cn.fujitsu.com>]

From: Chen Yang <chenyang.fnst@cn.fujitsu.com>
Date: Fri, 18 Jan 2013 14:54:31 +0800
Subject: [PATCH] Btrfs-progs/receive: sparse and pre-allocated file support
 for btrfs-send mechanism

When sending a file with sparse or pre-allocated part,
these parts will be sent as ZERO streams, and it's unnecessary.

To improve this, we add a punch command on the sending side, so the
receiving side changed with it. The main change is adding the punch
processing to receive command.

Signed-off-by: Cheng Yang <chenyang.fnst@cn.fujitsu.com>
---
 cmds-receive.c |   27 +++++++++++++++++++++++++++
 send-stream.c  |    6 ++++++
 send-stream.h  |    1 +
 send.h         |    3 ++-
 4 files changed, 36 insertions(+), 1 deletions(-)

diff --git a/cmds-receive.c b/cmds-receive.c
index a8be6fa..74cbfc4 100644
--- a/cmds-receive.c
+++ b/cmds-receive.c
@@ -37,6 +37,7 @@
 #include <sys/types.h>
 #include <sys/xattr.h>
 #include <uuid/uuid.h>
+#include <linux/falloc.h>
 
 #include "ctree.h"
 #include "ioctl.h"
@@ -508,6 +509,31 @@ out:
 	return ret;
 }
 
+static int process_punch(const char *path, u64 offset, u64 len, void *user)
+{
+	int ret = 0;
+	struct btrfs_receive *r = user;
+	char *full_path = path_cat(r->full_subvol_path, path);
+
+	ret = open_inode_for_write(r, full_path);
+	if (ret < 0)
+		goto out;
+
+	ret = fallocate(r->write_fd,
+		FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+		offset, len);
+	if (ret < 0) {
+		ret = -errno;
+		fprintf(stderr, "ERROR: punch %s failed. %s\n",
+				path, strerror(-ret));
+		goto out;
+	}
+
+out:
+	free(full_path);
+	return ret;
+}
+
 static int process_write(const char *path, const void *data, u64 offset,
 			 u64 len, void *user)
 {
@@ -777,6 +803,7 @@ struct btrfs_send_ops send_ops = {
 	.link = process_link,
 	.unlink = process_unlink,
 	.rmdir = process_rmdir,
+	.punch = process_punch,
 	.write = process_write,
 	.clone = process_clone,
 	.set_xattr = process_set_xattr,
diff --git a/send-stream.c b/send-stream.c
index 55fa728..9f3ede7 100644
--- a/send-stream.c
+++ b/send-stream.c
@@ -362,6 +362,12 @@ static int read_and_process_cmd(struct btrfs_send_stream *s)
 		TLV_GET_STRING(s, BTRFS_SEND_A_PATH, &path);
 		ret = s->ops->rmdir(path, s->user);
 		break;
+	case BTRFS_SEND_C_PUNCH:
+		TLV_GET_STRING(s, BTRFS_SEND_A_PATH, &path);
+		TLV_GET_U64(s, BTRFS_SEND_A_FILE_OFFSET, &offset);
+		TLV_GET_U64(s, BTRFS_SEND_A_SIZE, &len);
+		ret = s->ops->punch(path, offset, len, s->user);
+		break;
 	case BTRFS_SEND_C_WRITE:
 		TLV_GET_STRING(s, BTRFS_SEND_A_PATH, &path);
 		TLV_GET_U64(s, BTRFS_SEND_A_FILE_OFFSET, &offset);
diff --git a/send-stream.h b/send-stream.h
index b69b7f1..f83f2ac 100644
--- a/send-stream.h
+++ b/send-stream.h
@@ -34,6 +34,7 @@ struct btrfs_send_ops {
 	int (*link)(const char *path, const char *lnk, void *user);
 	int (*unlink)(const char *path, void *user);
 	int (*rmdir)(const char *path, void *user);
+	int (*punch)(const char *path, u64 offset, u64 len, void *user);
 	int (*write)(const char *path, const void *data, u64 offset, u64 len,
 		     void *user);
 	int (*clone)(const char *path, u64 offset, u64 len,
diff --git a/send.h b/send.h
index 9934e94..10a88d2 100644
--- a/send.h
+++ b/send.h
@@ -20,7 +20,7 @@
 #include "ctree.h"
 
 #define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
-#define BTRFS_SEND_STREAM_VERSION 1
+#define BTRFS_SEND_STREAM_VERSION 2
 
 #define BTRFS_SEND_BUF_SIZE (1024 * 64)
 #define BTRFS_SEND_READ_SIZE (1024 * 48)
@@ -80,6 +80,7 @@ enum btrfs_send_cmd {
 	BTRFS_SEND_C_WRITE,
 	BTRFS_SEND_C_CLONE,
 
+	BTRFS_SEND_C_PUNCH,
 	BTRFS_SEND_C_TRUNCATE,
 	BTRFS_SEND_C_CHMOD,
 	BTRFS_SEND_C_CHOWN,
-- 
1.7.7.6