storage: More precise ignoring of "other mounts"

We used to ignore all other mounts when the first one is for the root
filesystem. But filesystems can have more than one mount and we should
look at each one individually.

This also prepares the code for more cases.

pkg/storaged/filesystem/mismounting.jsx

@@ -45,13 +45,22 @@ export function check_mismounted_fsys(backing_block, content_block, fstab_config
     if (!(block_fsys || dir))
         return;
 
+    function ignore_mount(m) {
+        // We don't complain about the rootfs, it's probably
+        // configured somewhere else, like in the bootloader.
+        if (m == "/")
+            return true;
+
+        return false;
+    }
+
     const mounted_at = get_mount_points(client, block_fsys, subvol);
     const split_options = parse_options(opts);
     const opt_noauto = extract_option(split_options, "noauto");
     const opt_noauto_intent = extract_option(split_options, "x-cockpit-never-auto");
     const opt_systemd_automount = split_options.indexOf("x-systemd.automount") >= 0;
     const is_mounted = mounted_at.indexOf(dir) >= 0;
-    const other_mounts = mounted_at.filter(m => m != dir);
+    const other_mounts = mounted_at.filter(m => m != dir && !ignore_mount(m));
     const crypto_backing_noauto = get_cryptobacking_noauto(client, backing_block);
 
     let type;
@@ -68,10 +77,7 @@ export function check_mismounted_fsys(backing_block, content_block, fstab_config
         else if (is_mounted && opt_noauto && !opt_noauto_intent && !opt_systemd_automount)
             type = "no-mount-on-boot";
     } else if (other_mounts.length > 0) {
-        // We don't complain about the rootfs, it's probably
-        // configured somewhere else, like in the bootloader.
-        if (other_mounts[0] != "/")
-            type = "mounted-no-config";
+        type = "mounted-no-config";
     }
 
     if (type)

test/verify/check-storage-btrfs

@@ -507,11 +507,12 @@ class TestStorageBtrfs(storagelib.StorageCase):
         b.click(self.card_button("btrfs subvolume", f"Mount automatically on {mount_point} on boot"))
         b.wait_not_present(self.card_button("btrfs subvolume", f"Mount automatically on {mount_point} on boot"))
 
-        # No warnings on main page for either subvolumes
-        b.go("#/")
-        b.wait_visible(self.card("Storage"))
-        b.wait_not_present(self.card_row("Storage", name=subvol) + ' .ct-icon-exclamation-triangle')
-        b.wait_not_present(self.card_row("Storage", name="/") + ' .ct-icon-exclamation-triangle')
+        # No warnings for either subvolume
+        b.go(f"#/")
+        self.click_card_row("Storage", name=disk1)
+        b.wait_visible(self.card("btrfs filesystem"))
+        b.wait_not_present(self.card_row("btrfs filesystem", name=subvol) + ' .ct-icon-exclamation-triangle')
+        b.wait_not_present(self.card_row("btrfs filesystem", name="/") + ' .ct-icon-exclamation-triangle')
 
     def testLuksEncrypted(self):
         m = self.machine