umount: Resolve btrfs subvolume mountpoints

src/Makefile.am

@@ -89,6 +89,7 @@ libudisks_daemon_la_SOURCES =
 	udisksthreadedjob.h              udisksthreadedjob.c                     \
 	udiskssimplejob.h                udiskssimplejob.c                       \
 	udisksmount.h                    udisksmount.c                           \
+	udisksmountutil.h                                                          \
 	udisksmountmonitor.h             udisksmountmonitor.c                    \
 	udisksdaemonutil.h               udisksdaemonutil.c                      \
 	udiskslogging.h                  udiskslogging.c                         \

src/udisksmountmonitor.c

@@ -37,6 +37,7 @@
 #include "udiskslogging.h"
 #include "udisksmountmonitor.h"
 #include "udisksmount.h"
+#include "udisksmountutil.h"
 #include "udisksprivate.h"
 #include "udisksdaemonutil.h"
 
@@ -510,46 +511,8 @@ udisks_mount_monitor_parse_mountinfo (UDisksMountMonitor  *monitor,
        */
       if (major == 0)
         {
-          const gchar *sep;
-          sep = strstr (lines[n], " - ");
-          if (sep != NULL)
-            {
-              gchar fstype[PATH_MAX + 1];
-              gchar mount_source[PATH_MAX + 1];
-              struct stat statbuf;
-
-              if (sscanf (sep + 3, PATH_MAX_FMT " " PATH_MAX_FMT, fstype, mount_source) != 2)
-                {
-                  udisks_warning ("Error parsing things past - for '%s'", lines[n]);
-                  continue;
-                }
-              fstype[sizeof fstype - 1] = '\0';
-              mount_source[sizeof mount_source - 1] = '\0';
-
-              if (g_strcmp0 (fstype, "btrfs") != 0)
-                continue;
-
-              if (!g_str_has_prefix (mount_source, "/dev/"))
-                continue;
-
-              if (stat (mount_source, &statbuf) != 0)
-                {
-                  udisks_warning ("Error statting %s: %m", mount_source);
-                  continue;
-                }
-
-              if (!S_ISBLK (statbuf.st_mode))
-                {
-                  udisks_warning ("%s is not a block device", mount_source);
-                  continue;
-                }
-
-              dev = statbuf.st_rdev;
-            }
-          else
-            {
-              continue;
-            }
+          if (!udisks_mount_util_get_btrfs_device_from_mountinfo (lines[n], &dev))
+            continue;
         }
       else
         {

src/udisksmountutil.h

@@ -0,0 +1,72 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2026 Wang Yu <wangyu@uniontech.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#ifndef __UDISKS_MOUNT_UTIL_H__
+#define __UDISKS_MOUNT_UTIL_H__
+
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <glib.h>
+
+#define UDISKS_MOUNT_UTIL_XSTR(s) UDISKS_MOUNT_UTIL_STR(s)
+#define UDISKS_MOUNT_UTIL_STR(s) #s
+#define UDISKS_MOUNT_UTIL_PATH_MAX_FMT "%" UDISKS_MOUNT_UTIL_XSTR(PATH_MAX) "s"
+
+static gboolean
+udisks_mount_util_get_btrfs_device_from_mountinfo (const gchar *line,
+                                                    dev_t       *block_device)
+{
+  const gchar *sep;
+  gchar fstype[PATH_MAX + 1];
+  gchar mount_source[PATH_MAX + 1];
+  struct stat statbuf;
+
+  sep = strstr (line, " - ");
+  if (sep == NULL)
+    return FALSE;
+
+  if (sscanf (sep + 3,
+              UDISKS_MOUNT_UTIL_PATH_MAX_FMT " " UDISKS_MOUNT_UTIL_PATH_MAX_FMT,
+              fstype,
+              mount_source) != 2)
+    return FALSE;
+
+  fstype[sizeof fstype - 1] = '\0';
+  mount_source[sizeof mount_source - 1] = '\0';
+
+  if (g_strcmp0 (fstype, "btrfs") != 0 ||
+      !g_str_has_prefix (mount_source, "/dev/") ||
+      stat (mount_source, &statbuf) != 0 ||
+      !S_ISBLK (statbuf.st_mode))
+    return FALSE;
+
+  *block_device = statbuf.st_rdev;
+  return TRUE;
+}
+
+#undef UDISKS_MOUNT_UTIL_PATH_MAX_FMT
+#undef UDISKS_MOUNT_UTIL_STR
+#undef UDISKS_MOUNT_UTIL_XSTR
+
+#endif /* __UDISKS_MOUNT_UTIL_H__ */

tools/Makefile.am

@@ -43,6 +43,7 @@ sbin_PROGRAMS = umount.udisks2
 
 umount_udisks2_SOURCES =                                                       \
 	umount-udisks.c                                                        \
+	$(top_srcdir)/src/udisksmountutil.h                                    \
 	$(NULL)
 
 umount_udisks2_CFLAGS =                                                        \

tools/umount-udisks.c

@@ -28,9 +28,60 @@
 #include <sys/sysmacros.h>
 #include <unistd.h>
 #include <string.h>
+#include <limits.h>
 
 #include <udisks/udisks.h>
 
+#include "src/udisksmountutil.h"
+
+#define xstr(s) str(s)
+#define str(s) #s
+#define PATH_MAX_FMT "%" xstr(PATH_MAX) "s"
+#define PATH_MAX_SKIP_FMT "%*" xstr(PATH_MAX) "s"
+
+static gboolean
+lookup_block_device_for_mount_point (const gchar  *mount_point,
+                                     dev_t        *block_device)
+{
+  gchar *contents = NULL;
+  gchar **lines = NULL;
+  guint n;
+  gboolean ret = FALSE;
+
+  if (!g_file_get_contents ("/proc/self/mountinfo", &contents, NULL, NULL))
+    return FALSE;
+
+  lines = g_strsplit (contents, "\n", 0);
+  for (n = 0; lines[n] != NULL; n++)
+    {
+      gchar encoded_mount_point[PATH_MAX + 1];
+      gchar *decoded_mount_point;
+
+      if (strlen (lines[n]) == 0)
+        continue;
+
+      if (sscanf (lines[n],
+                  "%*u %*u %*u:%*u " PATH_MAX_SKIP_FMT " " PATH_MAX_FMT,
+                  encoded_mount_point) != 1)
+        continue;
+
+      encoded_mount_point[sizeof encoded_mount_point - 1] = '\0';
+      decoded_mount_point = g_strcompress (encoded_mount_point);
+
+      if (g_strcmp0 (decoded_mount_point, mount_point) == 0)
+        ret = udisks_mount_util_get_btrfs_device_from_mountinfo (lines[n], block_device);
+
+      g_free (decoded_mount_point);
+
+      if (ret)
+        break;
+    }
+
+  g_strfreev (lines);
+  g_free (contents);
+  return ret;
+}
+
 static UDisksObject *
 lookup_object_for_block (UDisksClient  *client,
                          dev_t          block_device)
@@ -94,7 +145,7 @@ main (int argc, char *argv[])
 
   if (S_ISBLK (statbuf.st_mode))
     block_device = statbuf.st_rdev;
-  else
+  else if (!lookup_block_device_for_mount_point (argv[1], &block_device))
     block_device = statbuf.st_dev;
 
   error = NULL;