Btrfs snapshot support

pkg/storaged/btrfs/subvolume.jsx

@@ -20,11 +20,12 @@
 import cockpit from "cockpit";
 import React from "react";
 
-import { CardBody } from "@patternfly/react-core/dist/esm/components/Card/index.js";
+import { Card, CardBody, CardHeader, CardTitle } from "@patternfly/react-core/dist/esm/components/Card/index.js";
 import { DescriptionList } from "@patternfly/react-core/dist/esm/components/DescriptionList/index.js";
 
 import {
-    StorageCard, StorageDescription, ChildrenTable, new_card, new_page, navigate_away_from_card
+    PageTable, StorageCard, StorageDescription, ChildrenTable,
+    new_card, new_page, navigate_away_from_card, register_crossref, get_crossrefs,
 } from "../pages.jsx";
 import { StorageUsageBar } from "../storage-controls.jsx";
 import {
@@ -395,6 +396,14 @@ function make_btrfs_subvolume_page(parent, volume, subvol, path_prefix, subvols)
         props: { subvol, mount_point, mismount_warning, block, fstab_config, forced_options },
         actions,
     });
+
+    if (subvol.id !== 5 && subvol.parent_uuid !== null)
+        register_crossref({
+            key: subvol.parent_uuid,
+            card,
+            size: mounted && <StorageUsageBar stats={use} short />,
+        });
+
     const page = new_page(parent, card);
     for (const sv of subvols) {
         if (sv.parent && (sv.parent === subvol.id || sv.parent === subvol.fake_id)) {
@@ -404,6 +413,7 @@ function make_btrfs_subvolume_page(parent, volume, subvol, path_prefix, subvols)
 }
 
 const BtrfsSubvolumeCard = ({ card, subvol, mismount_warning, block, fstab_config, forced_options }) => {
+    const crossrefs = get_crossrefs(subvol.uuid);
     return (
         <StorageCard card={card} alert={mismount_warning &&
         <MismountAlert warning={mismount_warning}
@@ -425,5 +435,17 @@ const BtrfsSubvolumeCard = ({ card, subvol, mismount_warning, block, fstab_confi
                                aria-label={_("btrfs subvolumes")}
                                page={card.page} />
             </CardBody>
+            {crossrefs &&
+            <Card data-test-card-title="Snapshots">
+                <CardHeader>
+                    <CardTitle component="h2">{_("Snapshots")}</CardTitle>
+                </CardHeader>
+                <CardBody className="contains-list">
+                    <PageTable emptyCaption={_("No snapshots found")}
+                                       aria-label={_("snapshot")}
+                                       crossrefs={crossrefs} />
+                </CardBody>
+            </Card>
+            }
         </StorageCard>);
 };

pkg/storaged/client.js

@@ -243,12 +243,18 @@ export async function btrfs_poll() {
                 // ID 256 gen 7 parent 5 top level 5 path <FS_TREE>/one
                 // ID 257 gen 7 parent 256 top level 256 path one/two
                 // ID 258 gen 7 parent 257 top level 257 path <FS_TREE>/one/two/three/four
-                const output = await cockpit.spawn(["btrfs", "subvolume", "list", "-ap", mount_point], { superuser: "require", err: "message" });
+                const output = await cockpit.spawn(["btrfs", "subvolume", "list", "-apuq", mount_point], { superuser: "require", err: "message" });
                 const subvols = [{ pathname: "/", id: 5, parent: null }];
                 for (const line of output.split("\n")) {
-                    const m = line.match(/ID (\d+).*parent (\d+).*path (<FS_TREE>\/)?(.*)/);
-                    if (m)
-                        subvols.push({ pathname: m[4], id: Number(m[1]), parent: Number(m[2]) });
+                    const m = line.match(/ID (\d+).*parent (\d+).*parent_uuid (.*)uuid (.*) path (<FS_TREE>\/)?(.*)/);
+                    if (m) {
+                        // The parent uuid is the uuid of which this subvolume is a snapshot.
+                        // https://github.com/torvalds/linux/blob/8d025e2092e29bfd13e56c78e22af25fac83c8ec/include/uapi/linux/btrfs.h#L885
+                        let parent_uuid = m[3].trim();
+                        // BTRFS_UUID_SIZE is 16
+                        parent_uuid = parent_uuid.length < 16 ? null : parent_uuid;
+                        subvols.push({ pathname: m[6], id: Number(m[1]), parent: Number(m[2]), uuid: m[4], parent_uuid });
+                    }
                 }
                 uuids_subvols[uuid] = subvols;
             } catch (err) {

test/verify/check-storage-btrfs

@@ -592,6 +592,35 @@ class TestStorageBtrfs(storagelib.StorageCase):
         b.wait_text(self.card_row_col("btrfs filesystem", row_name="home", col_index=3), "/mnt/home (not mounted)")
         b.wait_text(self.card_row_col("btrfs filesystem", row_name="backups", col_index=3), "/mnt/backups (not mounted)")
 
+    def testSnapshot(self):
+        m = self.machine
+        b = self.browser
+
+        disk = self.add_ram_disk(size=128)
+        mount_point = "/run/butter"
+
+        snapshot_dir = f"{mount_point}/snapshots"
+        subdir = f"{mount_point}/subdir"
+
+        m.execute(f"""
+            mkfs.btrfs -L butter {disk}
+            mkdir -p {mount_point}
+            mount {disk} {mount_point}
+            echo '{disk} {mount_point} auto defaults 0 0' >> /etc/fstab
+            btrfs subvolume create {subdir} {snapshot_dir} {subdir}/foo
+            btrfs subvolume snapshot {subdir} {snapshot_dir}/snap-1
+            btrfs subvolume snapshot {mount_point} {snapshot_dir}/snap-2
+        """)
+
+        self.login_and_go("/storage")
+
+        self.click_card_row("Storage", name=os.path.basename(subdir))
+        b.wait_text(self.card_desc("btrfs subvolume", "Name"), "subdir")
+        b.wait_visible(self.card_row("Snapshots", name="snap-1"))
+        # Normal subvolume does not show under snapshots
+        b.wait_visible(self.card_row("btrfs subvolume", name="foo"))
+        b.wait_not_present(self.card_row("Snapshots", name="foo"))
+
 
 if __name__ == '__main__':
     testlib.test_main()