[sheepdog] Preview - patch convertconfig part 1

[Jens WEBER]

Patch preview - what do you think?

This patch add a version number to the config file and can convert the config file if it structure has changed. Part 2 does converting.

Thanks, Jens

--- sheepdog-0.4.0-0+tek2b.orig/sheep/store.c
+++ sheepdog-0.4.0-0+tek2b/sheep/store.c
@@ -28,13 +28,34 @@
 #include "util.h"
 #include "farm/farm.h"
 
+#define CONFIGFILE_SIGNATURE   0x0000aaaa00000000
+#define CONFIGFILE_VERSION     3
+/* configfile version 3 */
 struct sheepdog_config {
+	uint64_t configversion;
 	uint64_t ctime;
 	uint64_t space;
 	uint16_t flags;
 	uint8_t copies;
 	uint8_t store[STORE_LEN];
 };
+/***** remove in > v0.5.0 *****/
+/* configfile version 2 */
+struct sheepdog_config_2 {
+	uint64_t ctime;
+	uint64_t space;
+	uint16_t flags;
+	uint8_t copies;
+	uint8_t store[STORE_LEN];
+};
+/***** remove in > v0.5.0 *****/
+/* configfile version 1 */
+struct sheepdog_config_1 {
+	uint64_t ctime;
+	uint16_t flags;
+	uint8_t copies;
+	uint8_t store[STORE_LEN];
+};
 
 char *obj_path;
 char *mnt_path;
@@ -401,12 +422,55 @@ static int init_jrnl_path(const char *ba
 
 static int init_config_path(const char *base_path)
 {
+	/*
+	 * read and convert config
+	 *  new config has a version in the first 8 bytes
+	 *  4 bytes version number
+	 *  4 bytes fix version signature
+	 */
+	int fd, ret;
+	uint64_t version;
+
 	config_path = zalloc(strlen(base_path) + strlen(CONFIG_PATH) + 1);
 	sprintf(config_path, "%s" CONFIG_PATH, base_path);
 
-	mknod(config_path, def_fmode, S_IFREG);
+	fd = open(config_path, O_RDONLY);
+	if (fd < 0)
+	{
+		/* new config file */
+		mknod(config_path, def_fmode, S_IFREG);
+		fd = open(config_path, O_DSYNC | O_WRONLY);
+		if (fd < 0)
+			return 1;
 
-	return 0;
+		version = CONFIGFILE_SIGNATURE | CONFIGFILE_VERSION;
+		ret = xpwrite(fd, &version, sizeof(version), offsetof(struct sheepdog_config, configversion));
+
+		close(fd);
+		if (ret != sizeof(version))
+			return 1;
+
+		return 0;
+	}
+
+	ret = xpread(fd, &version, sizeof(version),
+		     offsetof(struct sheepdog_config, configversion));
+	close(fd);
+
+	if (ret != sizeof(version))
+		return 1;
+	if ((version & CONFIGFILE_SIGNATURE) == CONFIGFILE_SIGNATURE)
+	{
+		version = version & 0x0000000011111111;
+		if (version == CONFIGFILE_VERSION)
+			return 0;
+		/* convert config file with version number */
+		/* unknown version */
+		return 1;
+	}
+	/***** remove in > v0.5.0 *****/
+	/* convert config files without version number */
+	return 1;
 }
 
 static int init_store_driver(void)