repart: support "nodatacow" in btrfs subvolumes

In btrfs-progs 6.15 it is planned to add a new parameter in mkfs.btrfs
--inode-flags, that can set attributes for subvolumes, directories, and
files.

The current supported attributes are "nodatacow", to disable CoW, and
"nodatasum", to disable the checksum.

This commit extend the "Subvolunes=" option to understand the
"nodatacow" flag for subvolums only.

If RepartOffline is enabled it will build the image without loopback
devices, using the correct --inode-flags parameters.

If RepartOffline is disabled it will use loopback devices and set the
btrfs attributes accordingly.

Signed-off-by: Alberto Planas <aplanas@suse.com>

src/basic/btrfs.h

@@ -1,7 +1,16 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
 
 #include "basic-forward.h"
 
+typedef enum BtrfsSubvolFlags {
+        BTRFS_SUBVOL_RO               = 1 << 0,
+        BTRFS_SUBVOL_NODATACOW        = 1 << 1,
+        _BTRFS_SUBVOL_FLAGS_MASK      = BTRFS_SUBVOL_NODATACOW|BTRFS_SUBVOL_RO,
+        _BTRFS_SUBVOL_FLAGS_INVALID   = -EINVAL,
+        _BTRFS_SUBVOL_FLAGS_ERRNO_MAX = -ERRNO_MAX, /* Ensure the whole errno range fits into this enum */
+} BtrfsSubvolFlags;
+
 int btrfs_validate_subvolume_name(const char *name);
 
 int btrfs_subvol_make(int dir_fd, const char *path);

src/basic/mkdir.c

@@ -9,6 +9,7 @@
 #include "fd-util.h"
 #include "format-util.h"
 #include "fs-util.h"
+#include "hashmap.h"
 #include "log.h"
 #include "mkdir.h"
 #include "path-util.h"
@@ -202,7 +203,7 @@ int mkdir_p_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, g
         return mkdir_p_internal(prefix, path, mode, uid, gid, flags, mkdirat_errno_wrapper);
 }
 
-int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, char **subvolumes) {
+int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, Hashmap *subvolumes) {
         _cleanup_free_ char *pp = NULL, *bn = NULL;
         _cleanup_close_ int dfd = -EBADF;
         int r;
@@ -237,10 +238,17 @@ int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mod
         if (r < 0)
                 return r;
 
+        XOpenFlags flags = 0;
+        if (hashmap_contains(subvolumes, p)) {
+                flags = XO_SUBVOLUME;
+                if ((PTR_TO_INT(hashmap_get(subvolumes, p)) & BTRFS_SUBVOL_NODATACOW))
+                        flags |= XO_NOCOW;
+        }
+
         _cleanup_close_ int nfd = xopenat_full(
                                 dfd, bn,
                                 O_DIRECTORY|O_CREAT|O_EXCL|O_NOFOLLOW|O_CLOEXEC,
-                                path_strv_contains(subvolumes, p) ? XO_SUBVOLUME : 0,
+                                flags,
                                 m);
         if (nfd == -EEXIST)
                 return 0;

src/basic/mkdir.h

@@ -22,7 +22,7 @@ static inline int mkdir_parents(const char *path, mode_t mode) {
 int mkdir_parents_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, gid_t gid, MkdirFlags flags);
 int mkdir_p(const char *path, mode_t mode);
 int mkdir_p_safe(const char *prefix, const char *path, mode_t mode, uid_t uid, gid_t gid, MkdirFlags flags);
-int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, char **subvolumes);
+int mkdir_p_root_full(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m, usec_t ts, Hashmap *subvolumes);
 static inline int mkdir_p_root(const char *root, const char *p, uid_t uid, gid_t gid, mode_t m) {
         return mkdir_p_root_full(root, p, uid, gid, m, USEC_INFINITY, NULL);
 }