btrfs-progs: subvolume: use BTRFS_IOC_SUBVOL_SYNC_WAIT for sync

Documentation/btrfs-filesystem.rst

@@ -118,7 +118,7 @@ defragment [options] <file>|<dir> [<file>|<dir>...]
                 compression. See also section *EXAMPLES*.
 
         -L|--level <level>
-                Since kernel 6.14 the compresison can also take the level parameter which will be used
+                Since kernel 6.15 the compresison can also take the level parameter which will be used
                 only for the defragmentation and overrides the eventual mount option compression level.
                 Valid levels depend on the compression algorithms: *zlib*
                 1..9, *lzo* does not have any levels, *zstd* the standard levels 1..15 and also the

Documentation/mkfs.btrfs.rst

@@ -213,6 +213,41 @@ OPTIONS
         :file:`hardlink1` and :file:`hardlink2` because :file:`hardlink3` will
         be inside a new subvolume.
 
+--inode-flags <flags>:<path>
+	Specify that *path* to have inode *flags*, other than the default one (which
+	implies data COW and data checksum).  The option *--rootdir* must also be
+	specified.  This option can be specified multiple times.
+
+	The supported flag(s) are:
+
+	* *nodatacow*: disable data COW, implies *nodatasum* for regular files.
+	* *nodatasum*: disable data checksum only.
+
+	*flags* can be separated by comma (*,*).
+
+	Children inodes will inherit the flags from their parent inodes, like the
+	following case:
+
+        .. code-block:: none
+
+		rootdir/
+		|- file1
+		|- file2
+		|- dir/
+		   |- file3
+
+	In that case, if *--inode-flags nodatacow:dir* is specified, both
+	:file:`dir` and :file:`file3` will have the *nodatacow* flag.
+
+	And this option also works with *--subvol* option, but the inode flag of
+	each subvolume is independent and will not inherit from the parent directory.
+	(The same as the kernel behavior.)
+
+        .. note::
+                Both *--inode-flags* and *--subvol* options are memory hungry,
+                will consume at least 8KiB for each option.  Please keep the
+                usage of both options to minimum.
+
 --shrink
         Shrink the filesystem to its minimal size, only works with *--rootdir* option.
 

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
@@ -1726,9 +1742,12 @@ static const char * const cmd_subvolume_sync_usage[] = {
 	"after deletion.",
 	"If no subvolume id is given, wait until all current deletion requests",
 	"are completed, but do not wait for subvolumes deleted meanwhile.",
-	"The status of subvolume ids is checked periodically.",
+	"The status of subvolume IDs is first checked by attempting to wait"
+	"via ioctl. If the ioctl is not supported or fails, the status is checked"
+	"periodically as a fallback.",
 	"",
 	OPTLINE("-s <N>", "sleep N seconds between checks (default: 1)"),
+	OPTLINE("-p", "use periodic checking instead of waiting via ioctl"),
 	NULL
 };
 
@@ -1740,6 +1759,7 @@ 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 periodic = false;
 
 	optind = 0;
 	while (1) {
@@ -1757,6 +1777,9 @@ static int cmd_subvolume_sync(const struct cmd_struct *cmd, int argc, char **arg
 				goto out;
 			}
 			break;
+		case 'p':
+			periodic = true;
+			break;
 		default:
 			usage_unknown_option(cmd, argv);
 		}
@@ -1814,7 +1837,16 @@ 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 (periodic) {
+		ret = wait_for_subvolume_cleaning(fd, id_count, ids, sleep_interval);
+	} else {
+		ret = wait_for_subvolume_sync(fd, id_count, ids);
+		if (ret) {
+			if (ret == -ENOTTY)
+				error("subvolume sync ioctl not supported in this kernel version, 6.13 and newer is required");
+			ret = wait_for_subvolume_cleaning(fd, id_count, ids, sleep_interval);
+		}
+	}
 
 out:
 	free(ids);