fs-util: add fd-based flavour of path_is_encrypted()

src/shared/blockdev-util.c

@@ -334,6 +334,22 @@ static int blockdev_is_encrypted(const char *sysfs_path, unsigned depth_left) {
         return found_encrypted;
 }
 
+int fd_is_encrypted(int fd) {
+        char p[SYS_BLOCK_PATH_MAX(NULL)];
+        dev_t devt;
+        int r;
+
+        r = get_block_device_fd(fd, &devt);
+        if (r < 0)
+                return r;
+        if (r == 0) /* doesn't have a block device */
+                return false;
+
+        xsprintf_sys_block_path(p, NULL, devt);
+
+        return blockdev_is_encrypted(p, 10 /* safety net: maximum recursion depth */);
+}
+
 int path_is_encrypted(const char *path) {
         char p[SYS_BLOCK_PATH_MAX(NULL)];
         dev_t devt;

src/shared/blockdev-util.h

@@ -24,4 +24,5 @@ int lock_whole_block_device(dev_t devt, int operation);
 
 int blockdev_partscan_enabled(int fd);
 
+int fd_is_encrypted(int fd);
 int path_is_encrypted(const char *path);