[PATCH blktests] tests/throtl: add a new test 009

[PATCH blktests] tests/throtl: add a new test 009

[Tao Cui]

From: Tao Cui <cuitao@kylinos.cn>

Test the boundary condition of removing a cgroup while it still has IO
queued in the blk-throttle queue.  The queued bios must be flushed through
without any blk-cgroup or blk-throttle warning.

The dmesg check matches any blk-cgroup / blk-throttle warning rather than a
single call site, so it is not tied to one symbol.

Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
See also the related blkcg "store blkcg in bio" RFC:
https://lore.kernel.org/r/20260804065313.2092022-1-yukuai@kernel.org

 tests/throtl/009     | 67 ++++++++++++++++++++++++++++++++++++++++++++
 tests/throtl/009.out |  2 ++
 2 files changed, 69 insertions(+)
 create mode 100755 tests/throtl/009
 create mode 100644 tests/throtl/009.out

diff --git a/tests/throtl/009 b/tests/throtl/009
new file mode 100755
index 0000000..1f4ed67
--- /dev/null
+++ b/tests/throtl/009
@@ -0,0 +1,67 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2026 Tao Cui <cuitao@kylinos.cn>
+#
+# Regression test for removing a cgroup while IO is still queued in the
+# blk-throttle queue.  The queued bios must be flushed without any
+# blk-cgroup or blk-throttle warning, and without leaking the blkg
+# reference they pin.
+
+. tests/throtl/rc
+
+THROTL_BLKDEV_TYPES="nullb"
+
+DESCRIPTION="queued throttled IO vs. cgroup removal must not warn"
+QUICK=1
+
+set_conditions() {
+	_set_throtl_blkdev_type "$@"
+}
+
+test() {
+	echo "Running ${TEST_NAME}"
+
+	if ! _set_up_throtl; then
+		return 1
+	fi
+
+	# Throttle reads so the bio queues in the throttle queue.
+	_throtl_set_limits rbps=4096
+
+	(
+		echo "$BASHPID" > "$CGROUP2_DIR/$THROTL_DIR/cgroup.procs"
+		exec dd if=/dev/"$THROTL_DEV" of=/dev/null bs=1M count=1 status=none
+	) &
+	local io_pid=$!
+	sleep 2
+
+	# Move the reader to the cgroup2 root so the throttle cgroup can be
+	# removed while its bio is still queued.  $CGROUP2_DIR has +io in its
+	# subtree_control and so cannot hold processes.
+	echo "$io_pid" > "$(_cgroup2_base_dir)/cgroup.procs"
+
+	# Remove the throttle cgroup while its bio is still queued.
+	rmdir "$CGROUP2_DIR/$THROTL_DIR"
+	sleep 3
+
+	kill "$io_pid" 2>/dev/null
+	wait "$io_pid" 2>/dev/null
+
+	# $THROTL_DIR is already gone; tear down the rest by hand.
+	if [[ $THROTL_CLEAR_CGROUP2_DIR_CONTROL_IO == true ]]; then
+		echo "-io" > "$CGROUP2_DIR/cgroup.subtree_control"
+	fi
+	if [[ $THROTL_CLEAR_BASE_SUBTREE_CONTROL_IO == true ]]; then
+		echo "-io" > "$(_cgroup2_base_dir)/cgroup.subtree_control"
+	fi
+	_exit_cgroup2
+	_exit_throtl_blkdev
+
+	if _dmesg_since_test_start | grep -qE "WARNING:.*(blk-cgroup|blk-throttle)"; then
+		echo "WARNING: blkcg/blk-throttle warning on cgroup removal with queued IO"
+		_dmesg_since_test_start | grep -A 12 -E "WARNING:.*(blk-cgroup|blk-throttle)" \
+			>> "$FULL"
+	fi
+
+	echo "Test complete"
+}
diff --git a/tests/throtl/009.out b/tests/throtl/009.out
new file mode 100644
index 0000000..be675dd
--- /dev/null
+++ b/tests/throtl/009.out
@@ -0,0 +1,2 @@
+Running throtl/009
+Test complete
-- 
2.43.0

Re: [PATCH blktests] tests/throtl: add a new test 009

[Shin'ichiro Kawasaki]

On Aug 13, 2026 / 22:40, Tao Cui wrote:
> From: Tao Cui <cuitao@kylinos.cn>
> 
> Test the boundary condition of removing a cgroup while it still has IO
> queued in the blk-throttle queue.  The queued bios must be flushed through
> without any blk-cgroup or blk-throttle warning.
> 
> The dmesg check matches any blk-cgroup / blk-throttle warning rather than a
> single call site, so it is not tied to one symbol.

Tao, thanks for the patch. Does this test case have corresponding kernel side
fix? I'm guessing that your recent kernel patch is the fix. If so, I suggest
to mention the kernel commit in here and the test case header comment below.

> 
> Signed-off-by: Tao Cui <cuitao@kylinos.cn>
> ---
> See also the related blkcg "store blkcg in bio" RFC:
> https://lore.kernel.org/r/20260804065313.2092022-1-yukuai@kernel.org
> 
>  tests/throtl/009     | 67 ++++++++++++++++++++++++++++++++++++++++++++
>  tests/throtl/009.out |  2 ++
>  2 files changed, 69 insertions(+)
>  create mode 100755 tests/throtl/009
>  create mode 100644 tests/throtl/009.out
> 
> diff --git a/tests/throtl/009 b/tests/throtl/009
> new file mode 100755
> index 0000000..1f4ed67
> --- /dev/null
> +++ b/tests/throtl/009
> @@ -0,0 +1,67 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-3.0+
> +# Copyright (C) 2026 Tao Cui <cuitao@kylinos.cn>
> +#
> +# Regression test for removing a cgroup while IO is still queued in the
> +# blk-throttle queue.  The queued bios must be flushed without any
> +# blk-cgroup or blk-throttle warning, and without leaking the blkg
> +# reference they pin.
> +
> +. tests/throtl/rc
> +
> +THROTL_BLKDEV_TYPES="nullb"

Is there any reason to run this test case only for nullb? If not, I suggest to
remove the line above to run it for both nullb and scsi_debug.