From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 11 Mar 2025 10:43:17 +0000 (+0100)
Subject: mountfsd: also return suggested mount point paths for the returned partitions
X-Git-Tag: v258-rc1~1112^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0ecfcc9790d8efced4372097aa49857b117a0d9f;p=thirdparty%2Fsystemd.git

mountfsd: also return suggested mount point paths for the returned partitions

When mounting a disk image we return a bunch of mount fds referencing
the various partitions in the disk, along with some metadata about them.
One key metadata field is the "designator" which is supposed to tell
clients what is what, and where to mount it.

Let's make this more explicit: let's also include the literal relative
path where each mount shall be placed, to simplify implementations of
clients that do not care about the concept of designators.
---

diff --git a/src/mountfsd/mountwork.c b/src/mountfsd/mountwork.c
index ded0f3c4bca..eaf72893aab 100644
--- a/src/mountfsd/mountwork.c
+++ b/src/mountfsd/mountwork.c
@@ -510,6 +510,14 @@ static int vl_method_mount_image(
 
                 TAKE_FD(pp->fsmount_fd);
 
+                const char *m = partition_mountpoint_to_string(d);
+                _cleanup_strv_free_ char **l = NULL;
+                if (!isempty(m)) {
+                        l = strv_split_nulstr(m);
+                        if (!l)
+                                return log_oom_debug();
+                }
+
                 r = sd_json_variant_append_arraybo(
                                 &aj,
                                 SD_JSON_BUILD_PAIR("designator", SD_JSON_BUILD_STRING(partition_designator_to_string(d))),
@@ -522,7 +530,8 @@ static int vl_method_mount_image(
                                 SD_JSON_BUILD_PAIR_CONDITION(!!pp->label, "partitionLabel", SD_JSON_BUILD_STRING(pp->label)),
                                 SD_JSON_BUILD_PAIR("size", SD_JSON_BUILD_INTEGER(pp->size)),
                                 SD_JSON_BUILD_PAIR("offset", SD_JSON_BUILD_INTEGER(pp->offset)),
-                                SD_JSON_BUILD_PAIR("mountFileDescriptor", SD_JSON_BUILD_INTEGER(fd_idx)));
+                                SD_JSON_BUILD_PAIR("mountFileDescriptor", SD_JSON_BUILD_INTEGER(fd_idx)),
+                                JSON_BUILD_PAIR_STRV_NON_EMPTY("mountPoint", l));
                 if (r < 0)
                         return r;
         }
diff --git a/src/shared/gpt.c b/src/shared/gpt.c
index 9d7ffcecd9d..a443cc5e993 100644
--- a/src/shared/gpt.c
+++ b/src/shared/gpt.c
@@ -115,7 +115,7 @@ static const char *const partition_mountpoint_table[_PARTITION_DESIGNATOR_MAX] =
         [PARTITION_VAR]                       = "/var\0",
 };
 
-DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(partition_mountpoint, PartitionDesignator);
+DEFINE_STRING_TABLE_LOOKUP_TO_STRING(partition_mountpoint, PartitionDesignator);
 
 #define _GPT_ARCH_SEXTET(arch, name)                                   \
         { SD_GPT_ROOT_##arch,              "root-" name,               ARCHITECTURE_##arch, .designator = PARTITION_ROOT            },  \
diff --git a/src/shared/gpt.h b/src/shared/gpt.h
index e64ba8439d3..7a67eddebee 100644
--- a/src/shared/gpt.h
+++ b/src/shared/gpt.h
@@ -41,6 +41,8 @@ PartitionDesignator partition_verity_sig_to_data(PartitionDesignator d);
 const char* partition_designator_to_string(PartitionDesignator d) _const_;
 PartitionDesignator partition_designator_from_string(const char *name) _pure_;
 
+const char* partition_mountpoint_to_string(PartitionDesignator d) _const_;
+
 const char* gpt_partition_type_uuid_to_string(sd_id128_t id);
 const char* gpt_partition_type_uuid_to_string_harder(
                 sd_id128_t id,
diff --git a/src/shared/varlink-io.systemd.MountFileSystem.c b/src/shared/varlink-io.systemd.MountFileSystem.c
index 977552dd2d1..54f500a7c5b 100644
--- a/src/shared/varlink-io.systemd.MountFileSystem.c
+++ b/src/shared/varlink-io.systemd.MountFileSystem.c
@@ -42,7 +42,9 @@ static SD_VARLINK_DEFINE_STRUCT_TYPE(
                 SD_VARLINK_FIELD_COMMENT("The start offset of the partition in bytes."),
                 SD_VARLINK_DEFINE_FIELD(offset, SD_VARLINK_INT, 0),
                 SD_VARLINK_FIELD_COMMENT("A mount file descriptor to assign to a location."),
-                SD_VARLINK_DEFINE_FIELD(mountFileDescriptor, SD_VARLINK_INT, 0));
+                SD_VARLINK_DEFINE_FIELD(mountFileDescriptor, SD_VARLINK_INT, 0),
+                SD_VARLINK_FIELD_COMMENT("A relative path indicating the intended mount point for this file system, if applicable. May contain multiple paths, for certain partitions that can be mounted to multiple distinct places."),
+                SD_VARLINK_DEFINE_FIELD(mountPoint, SD_VARLINK_STRING, SD_VARLINK_NULLABLE|SD_VARLINK_ARRAY));
 
 static SD_VARLINK_DEFINE_METHOD(
                 MountImage,