btrfs: test incremental send after deleting directories with many hardlinks

Test that an incremental send works after we removed directories that have
large number of hardlinks for the same file (so that we have extrefs).

This is a regression test for the kernel commit 1fabe43b4e1a ("btrfs:
send: fix duplicated rmdir operations when using extrefs").

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/tests/btrfs/338 b/tests/btrfs/338
new file mode 100755 (executable)
index 0000000..0cc29c7
--- /dev/null
+++ b/tests/btrfs/338
@@ -0,0 +1,93 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 SUSE S.A.  All Rights Reserved.
+#
+# FS QA Test 338
+#
+# Test that an incremental send works after we removed directories that have
+# large number of hardlinks for the same file (so that we have extrefs).
+#
+. ./common/preamble
+_begin_fstest auto quick send
+
+_cleanup()
+{
+       cd /
+       rm -fr $tmp.*
+       rm -fr $send_files_dir
+}
+
+_require_test
+_require_scratch
+_require_fssum
+
+_fixed_by_kernel_commit 1fabe43b4e1a \
+       "btrfs: send: fix duplicated rmdir operations when using extrefs"
+
+send_files_dir=$TEST_DIR/btrfs-test-$seq
+
+rm -fr $send_files_dir
+mkdir $send_files_dir
+
+first_stream="$send_files_dir/1.send"
+second_stream="$send_files_dir/2.send"
+first_fssum="$send_files_dir/snap1.fssum"
+second_fssum="$send_files_dir/snap2.fssum"
+
+_scratch_mkfs >> $seqres.full 2>&1 || _fail "first mkfs failed"
+_scratch_mount
+
+# Create two directories which will have many hardlinks for the same file, a
+# large number that triggers the use of extrefs. This way we will get many
+# extref items in the subvolume tree, with a very high likelyhood that not
+# all hardlinks for directory "a" are consecutive in the tree, that they are
+# interspersed with extref items for hardlinks to directory "b".
+#
+# Example:
+#
+#        item 0 key (259 INODE_EXTREF 2309449) itemoff 16257 itemsize 26
+#                index 6925 parent 257 namelen 8 name: foo.6923
+#        item 1 key (259 INODE_EXTREF 2311350) itemoff 16231 itemsize 26
+#                index 6588 parent 258 namelen 8 name: foo.6587
+#        item 2 key (259 INODE_EXTREF 2457395) itemoff 16205 itemsize 26
+#                index 6611 parent 257 namelen 8 name: foo.6609
+#        (...)
+#
+# Refer to the kernel commit's changelog for more details.
+mkdir $SCRATCH_MNT/a
+mkdir $SCRATCH_MNT/b
+
+touch $SCRATCH_MNT/a/foo
+for ((i = 1; i <= 1000; i++)); do
+       ln $SCRATCH_MNT/a/foo $SCRATCH_MNT/a/foo.$i
+       ln $SCRATCH_MNT/a/foo $SCRATCH_MNT/b/foo.$i
+done
+
+_btrfs subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/snap1
+
+# Now delete the directories and all the links inside them.
+rm -fr $SCRATCH_MNT/a
+rm -fr $SCRATCH_MNT/b
+
+_btrfs subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/snap2
+
+_btrfs send -f $first_stream $SCRATCH_MNT/snap1
+_btrfs send -f $second_stream -p $SCRATCH_MNT/snap1 $SCRATCH_MNT/snap2
+
+$FSSUM_PROG -A -f -w $first_fssum $SCRATCH_MNT/snap1
+$FSSUM_PROG -A -f -w $second_fssum -x $SCRATCH_MNT/snap2/snap1 \
+       $SCRATCH_MNT/snap2
+
+# Create a new fs and apply both send streams.
+_scratch_unmount
+_scratch_mkfs >> $seqres.full 2>&1 || _fail "second mkfs failed"
+_scratch_mount
+
+_btrfs receive -f $first_stream $SCRATCH_MNT
+_btrfs receive -f $second_stream $SCRATCH_MNT
+
+$FSSUM_PROG -r $first_fssum $SCRATCH_MNT/snap1
+$FSSUM_PROG -r $second_fssum $SCRATCH_MNT/snap2
+
+# success, all done
+_exit 0

diff --git a/tests/btrfs/338.out b/tests/btrfs/338.out
new file mode 100644 (file)
index 0000000..7ea6181
--- /dev/null
+++ b/tests/btrfs/338.out
@@ -0,0 +1,3 @@
+QA output created by 338
+OK
+OK