btrfs-progs: subvolume: use BTRFS_IOC_SUBVOL_SYNC_WAIT for sync

This patch uses BTRFS_IOC_SUBVOL_SYNC_WAIT ioctl in subvolume sync
command before checking periodically and adds an option to not to
use sync wait ioctl call and force to check periodically. This
patch calls a new function wait_for_subvolume_sync() that calls
BTRFS_IOC_SUBVOL_SYNC_WAIT for each subvol.

Issue: #953
Signed-off-by: Sidong Yang <[email protected]>

Author: SidongYang

cmds/subvolume.c

@@ -122,6 +122,22 @@ static int wait_for_subvolume_cleaning(int fd, size_t count, uint64_t *ids,
 	return 0;
 }
 
+static int wait_for_subvolume_sync(int fd, size_t count, uint64_t *ids) {
+	int i, ret;
+	struct btrfs_ioctl_subvol_wait arg;
+
+	for (i=0; i<count; ++i) {
+		arg.subvolid = ids[i];
+		arg.mode = BTRFS_SUBVOL_SYNC_WAIT_FOR_ONE;
+
+		ret = ioctl(fd, BTRFS_IOC_SUBVOL_SYNC_WAIT, &arg);
+
+		if (ret && errno != ENOENT)
+			return -errno;
+	}
+	return 0;
+}
+
 static const char * const subvolume_cmd_group_usage[] = {
 	"btrfs subvolume <command> <args>",
 	NULL
@@ -1729,6 +1745,7 @@ static const char * const cmd_subvolume_sync_usage[] = {
 	"The status of subvolume ids is checked periodically.",
 	"",
 	OPTLINE("-s <N>", "sleep N seconds between checks (default: 1)"),
+	OPTLINE("-f", "force to check periodically (default: false)"),
 	NULL
 };
 
@@ -1740,6 +1757,7 @@ static int cmd_subvolume_sync(const struct cmd_struct *cmd, int argc, char **arg
 	size_t id_count, i;
 	int sleep_interval = 1;
 	enum btrfs_util_error err;
+	bool force_to_check = false;
 
 	optind = 0;
 	while (1) {
@@ -1757,6 +1775,8 @@ static int cmd_subvolume_sync(const struct cmd_struct *cmd, int argc, char **arg
 				goto out;
 			}
 			break;
+		case 'f':
+			force_to_check = true;
 		default:
 			usage_unknown_option(cmd, argv);
 		}
@@ -1814,7 +1834,13 @@ static int cmd_subvolume_sync(const struct cmd_struct *cmd, int argc, char **arg
 		}
 	}
 
-	ret = wait_for_subvolume_cleaning(fd, id_count, ids, sleep_interval);
+	if (force_to_check) {
+		ret = wait_for_subvolume_cleaning(fd, id_count, ids, sleep_interval);
+	} else {
+		ret = wait_for_subvolume_sync(fd, id_count, ids);
+		if (ret)
+			ret = wait_for_subvolume_cleaning(fd, id_count, ids, sleep_interval);
+	}
 
 out:
 	free(ids);