machined/machinectl: add logic to show list of available images

This adds a new bus call to machined that enumerates /var/lib/container
and returns all trees stored in it, distuingishing three types:

        - GPT disk images, which are files suffixed with ".gpt"
        - directory trees
        - btrfs subvolumes

3 files changed, 25 insertions, 6 deletions

diff --git a/src/shared/btrfs-util.c b/src/shared/btrfs-util.c
index 492d7fc777..d685b3ecbd 100644
--- a/src/shared/btrfs-util.c
+++ b/src/shared/btrfs-util.c
@@ -84,18 +84,18 @@ int btrfs_is_snapshot(int fd) {
         struct stat st;
         struct statfs sfs;
 
-        if (fstatfs(fd, &sfs) < 0)
+        /* On btrfs subvolumes always have the inode 256 */
+
+        if (fstat(fd, &st) < 0)
                 return -errno;
 
-        if (!F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC))
+        if (!S_ISDIR(st.st_mode) || st.st_ino != 256)
                 return 0;
 
-        if (fstat(fd, &st) < 0)
+        if (fstatfs(fd, &sfs) < 0)
                 return -errno;
 
-        /* On btrfs subvolumes always have the inode 256 */
-
-        return S_ISDIR(st.st_mode) && st.st_ino == 256;
+        return F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC);
 }
 
 int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy) {
@@ -232,6 +232,15 @@ int btrfs_subvol_read_only(const char *path, bool b) {
         return 0;
 }
 
+int btrfs_subvol_is_read_only_fd(int fd) {
+        uint64_t flags;
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
+                return -errno;
+
+        return !!(flags & BTRFS_SUBVOL_RDONLY);
+}
+
 int btrfs_reflink(int infd, int outfd) {
         int r;
 
diff --git a/src/shared/btrfs-util.h b/src/shared/btrfs-util.h
index 28dbeb4e27..c8f798b6a6 100644
--- a/src/shared/btrfs-util.h
+++ b/src/shared/btrfs-util.h
@@ -28,6 +28,7 @@ int btrfs_subvol_make(const char *path);
 int btrfs_subvol_remove(const char *path);
 int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy);
 int btrfs_subvol_read_only(const char *path, bool b);
+int btrfs_subvol_is_read_only_fd(int fd);
 
 int btrfs_reflink(int infd, int outfd);
 
diff --git a/src/shared/util.h b/src/shared/util.h
index 96b8c1bcc0..e783ec6cdb 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -775,6 +775,15 @@ int search_and_fopen_nulstr(const char *path, const char *mode, const char *root
                         continue;                                       \
                 else
 
+#define FOREACH_DIRENT_ALL(de, d, on_error)                             \
+        for (errno = 0, de = readdir(d);; errno = 0, de = readdir(d))   \
+                if (!de) {                                              \
+                        if (errno > 0) {                                \
+                                on_error;                               \
+                        }                                               \
+                        break;                                          \
+                } else
+
 static inline void *mempset(void *s, int c, size_t n) {
         memset(s, c, n);
         return (uint8_t*)s + n;