btrfs-progs: receive: cannot find clone source subvol when receiving in reverse direction

process_clone() only searches the received_uuid, but could exist in an
earlier uuid that isn't the received_uuid.  Mirror what process_snapshot
does and search both the received_uuid and if that fails look up by
normal uuid.

Fixes: https://github.com/kdave/btrfs-progs/issues/606

Issue: #606
Pull-request: #643
Pull-request: #862
Signed-off-by: Arsenii Skvortsov <ettavolt@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

cmds/receive.c

@@ -221,6 +221,25 @@ out:
 	return ret;
 }
 
+/*
+ * Search for the @subvol_uuid, try received_uuid and subvolume as a fallback
+ * if it's not found.
+ */
+static struct subvol_info *search_source_subvol(int mnt_fd, const u8 *subvol_uuid,
+						u64 transid)
+{
+	struct subvol_info *found;
+
+	found = subvol_uuid_search(mnt_fd, 0, subvol_uuid, transid, NULL,
+				   subvol_search_by_received_uuid);
+	if (IS_ERR_OR_NULL(found)) {
+		found = subvol_uuid_search(mnt_fd, 0, subvol_uuid, transid,
+					   NULL, subvol_search_by_uuid);
+	}
+
+	return found;
+}
+
 static int process_snapshot(const char *path, const u8 *uuid, u64 ctransid,
 			    const u8 *parent_uuid, u64 parent_ctransid,
 			    void *user)
@@ -283,14 +302,8 @@ static int process_snapshot(const char *path, const u8 *uuid, u64 ctransid,
 	memset(&args_v2, 0, sizeof(args_v2));
 	strncpy_null(args_v2.name, path, sizeof(args_v2.name));
 
-	parent_subvol = subvol_uuid_search(rctx->mnt_fd, 0, parent_uuid,
+	parent_subvol = search_source_subvol(rctx->mnt_fd, parent_uuid,
-					   parent_ctransid, NULL,
+					     parent_ctransid);
-					   subvol_search_by_received_uuid);
-	if (IS_ERR_OR_NULL(parent_subvol)) {
-		parent_subvol = subvol_uuid_search(rctx->mnt_fd, 0, parent_uuid,
-						   parent_ctransid, NULL,
-						   subvol_search_by_uuid);
-	}
 	if (IS_ERR_OR_NULL(parent_subvol)) {
 		if (!parent_subvol)
 			ret = -ENOENT;
@@ -745,9 +758,8 @@ static int process_clone(const char *path, u64 offset, u64 len,
 		   BTRFS_UUID_SIZE) == 0) {
 		subvol_path = rctx->cur_subvol_path;
 	} else {
-		si = subvol_uuid_search(rctx->mnt_fd, 0, clone_uuid, clone_ctransid,
+		si = search_source_subvol(rctx->mnt_fd, clone_uuid,
-					NULL,
+					  clone_ctransid);
-					subvol_search_by_received_uuid);
 		if (IS_ERR_OR_NULL(si)) {
 			char uuid_str[BTRFS_UUID_UNPARSED_SIZE];
 

tests/misc-tests/064-reverse-receive/test.sh

@@ -0,0 +1,99 @@
+#!/bin/bash
+#
+# Receive in reverse direction must not throw an error if it can find an
+# earlier "sent" parent.  In general, shows a backup+sync setup between two (or
+# more) PCs with an external drive.
+
+source "$TEST_TOP/common"
+
+check_prereq mkfs.btrfs
+check_prereq btrfs
+check_global_prereq dd
+
+declare -a roots
+i_pc1=1
+# An external drive used to backup and carry profile.
+i_ext=2
+i_pc2=3
+roots[$i_pc1]="$TEST_MNT/pc1"
+roots[$i_ext]="$TEST_MNT/external"
+roots[$i_pc2]="$TEST_MNT/pc2"
+
+setup_root_helper
+mkdir -p "${roots[@]}"
+setup_loopdevs 3
+prepare_loopdevs
+for i in `seq 3`; do
+	TEST_DEV="${loopdevs[$i]}"
+	TEST_MNT="${roots[$i]}"
+	run_check_mkfs_test_dev
+	run_check_mount_test_dev
+	run_check $SUDO_HELPER mkdir -p "$TEST_MNT/.snapshots"
+done
+
+run_check_update_file()
+{
+	run_check $SUDO_HELPER cp --reflink "${roots[$1]}/profile/$2" "${roots[$1]}/profile/staging"
+	run_check $SUDO_HELPER dd if=/dev/urandom conv=notrunc bs=4K count=4 seek=$3 "of=${roots[$1]}/profile/staging"
+	run_check $SUDO_HELPER mv "${roots[$1]}/profile/staging" "${roots[$1]}/profile/$2"
+}
+run_check_copy_snapshot_with_diff()
+{
+	_mktemp_local send.data
+	run_check $SUDO_HELPER "$TOP/btrfs" send -f send.data -p "${roots[$1]}/.snapshots/$2" "${roots[$1]}/.snapshots/$3"
+	run_check $SUDO_HELPER "$TOP/btrfs" receive -f send.data "${roots[$4]}/.snapshots"
+}
+run_check_backup_profile()
+{
+	run_check $SUDO_HELPER "$TOP/btrfs" subvolume snapshot -r "${roots[$1]}/profile" "${roots[$1]}/.snapshots/$3"
+	run_check_copy_snapshot_with_diff "$1" "$2" "$3" "$i_ext"
+	# Don't keep old snapshot in pc
+	run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete "${roots[$1]}/.snapshots/$2"
+}
+run_check_restore_profile()
+{
+	run_check $SUDO_HELPER "$TOP/btrfs" subvolume snapshot "${roots[$1]}/.snapshots/$2" "${roots[$1]}/profile"
+}
+run_check_copy_fresh_backup_and_replace_profile()
+{
+    run_check_copy_snapshot_with_diff "$i_ext" "$2" "$3" "$1"
+    # IRL, it would be a nice idea to make a backup snapshot before deleting.
+    run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete "${roots[$1]}/profile"
+    run_check_restore_profile "$1" "$3"
+    # Don't keep old snapshot in pc
+    run_check $SUDO_HELPER "$TOP/btrfs" subvolume delete "${roots[$1]}/.snapshots/$2"
+}
+
+
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume create "${roots[$i_pc1]}/profile"
+run_check $SUDO_HELPER dd if=/dev/urandom bs=4K count=16 "of=${roots[$i_pc1]}/profile/day1"
+run_check $SUDO_HELPER "$TOP/btrfs" subvolume snapshot -r "${roots[$i_pc1]}/profile" "${roots[$i_pc1]}/.snapshots/day1"
+_mktemp_local send.data
+run_check $SUDO_HELPER "$TOP/btrfs" send -f send.data "${roots[$i_pc1]}/.snapshots/day1"
+run_check $SUDO_HELPER "$TOP/btrfs" receive -f send.data "${roots[$i_ext]}/.snapshots"
+
+run_check_update_file "$i_pc1" day1 2
+run_check_backup_profile "$i_pc1" day1 day2
+
+_mktemp_local send.data
+run_check $SUDO_HELPER "$TOP/btrfs" send -f send.data "${roots[$i_ext]}/.snapshots/day2"
+run_check $SUDO_HELPER "$TOP/btrfs" receive -f send.data "${roots[$i_pc2]}/.snapshots"
+run_check_restore_profile "$i_pc2" day2
+run_check_update_file "$i_pc2" day1 3
+run_check_backup_profile "$i_pc2" day2 day3
+
+run_check_update_file "$i_pc2" day1 4
+run_check_backup_profile "$i_pc2" day3 day4
+
+run_check_copy_fresh_backup_and_replace_profile "$i_pc1" day2 day4
+run_check_update_file "$i_pc1" day1 5
+run_check_backup_profile "$i_pc1" day4 day5
+
+run_check_copy_fresh_backup_and_replace_profile "$i_pc2" day4 day5
+run_check_update_file "$i_pc2" day1 6
+run_check_backup_profile "$i_pc2" day5 day6
+
+run_check_umount_test_dev "${loopdevs[@]}"
+rmdir "${roots[@]}"
+rm -f send.data
+cleanup_loopdevs