From: Mike Yuan <me@yhndnzj.com>
Date: Mon, 10 Jun 2024 15:43:52 +0000 (+0200)
Subject: mount-util: clean up mount_exchange_graceful a bit, don't duplicate move_mount when... 
X-Git-Tag: v257-rc1~831^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=706302897acdcbe442de6e5c66023938675cee8d;p=thirdparty%2Fsystemd.git

mount-util: clean up mount_exchange_graceful a bit, don't duplicate move_mount when fallback
---

diff --git a/src/shared/mount-util.c b/src/shared/mount-util.c
index 7e18d12df45..0b3154fbd90 100644
--- a/src/shared/mount-util.c
+++ b/src/shared/mount-util.c
@@ -759,27 +759,19 @@ int mount_exchange_graceful(int fsmount_fd, const char *dest, bool mount_beneath
          * this is not supported (minimum kernel v6.5), or if there is no mount on the mountpoint, we get
          * -EINVAL and then we fallback to normal mounting. */
 
-        r = RET_NERRNO(move_mount(
-                        fsmount_fd,
-                        /* from_path= */ "",
-                        /* to_fd= */ -EBADF,
-                        dest,
-                        MOVE_MOUNT_F_EMPTY_PATH | (mount_beneath ? MOVE_MOUNT_BENEATH : 0)));
+        r = RET_NERRNO(move_mount(fsmount_fd, /* from_path = */ "",
+                                  /* to_fd = */ -EBADF, dest,
+                                  MOVE_MOUNT_F_EMPTY_PATH | (mount_beneath ? MOVE_MOUNT_BENEATH : 0)));
         if (mount_beneath) {
+                if (r >= 0) /* Mounting beneath worked! Now unmount the upper mount. */
+                        return umount_verbose(LOG_DEBUG, dest, UMOUNT_NOFOLLOW|MNT_DETACH);
+
                 if (r == -EINVAL) { /* Fallback if mount_beneath is not supported */
                         log_debug_errno(r,
-                                        "Failed to mount beneath '%s', falling back to overmount",
+                                        "Cannot mount beneath '%s', falling back to overmount: %m",
                                         dest);
-                        return RET_NERRNO(move_mount(
-                                        fsmount_fd,
-                                        /* from_path= */ "",
-                                        /* to_fd= */ -EBADF,
-                                        dest,
-                                        MOVE_MOUNT_F_EMPTY_PATH));
+                        return mount_exchange_graceful(fsmount_fd, dest, /* mount_beneath = */ false);
                 }
-
-                if (r >= 0) /* If it is, now remove the old mount */
-                        return umount_verbose(LOG_DEBUG, dest, UMOUNT_NOFOLLOW|MNT_DETACH);
         }
 
         return r;