block/020: test IO req allocation

IO request allocation may hang for ever if the allocation process
migrages. This test covers the request allocation code path.

The following patch can fix this issue on linus kernel:

https://marc.info/?l=linux-block&m=152671586923185&w=2

Signed-off-by: Ming Lei <ming.lei@redhat.com>
[Omar: clarify comment and description]
Signed-off-by: Omar Sandoval <osandov@fb.com>

diff --git a/tests/block/020 b/tests/block/020
new file mode 100755 (executable)
index 0000000..40a8151
--- /dev/null
+++ b/tests/block/020
@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Test blk-mq request allocation when hardware tags are limited. Regression
+# test for commit e6fc46498784 ("blk-mq: avoid starving tag allocation after
+# allocating process migrates").
+#
+# Copyright (C) 2018 Ming Lei <ming.lei@redhat.com>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+DESCRIPTION="run null-blk on different schedulers with only one hardware tag"
+QUICK=1
+
+requires() {
+       _have_module null_blk && _have_fio
+}
+
+test() {
+       echo "Running ${TEST_NAME}"
+
+       modprobe -r null_blk
+       modprobe null_blk queue_mode=2 irqmode=2 completion_nsec=2000000 \
+               shared_tags=1 submit_queues=4 hw_queue_depth=1
+
+       local scheds
+       # shellcheck disable=SC2207
+       scheds=($(sed 's/[][]//g' /sys/block/nullb0/queue/scheduler))
+
+       for sched in "${scheds[@]}"; do
+               echo "Testing $sched" >> "$FULL"
+               echo "$sched" > /sys/block/nullb0/queue/scheduler
+               _fio_perf --bs=4k --ioengine=libaio --iodepth=1024 \
+                       --numjobs="$(nproc)" --rw=randread --name=async \
+                       --filename=/dev/nullb0 --size=1g --direct=1 \
+                       --runtime=10
+       done
+
+       modprobe -r null_blk
+
+       echo "Test complete"
+}

diff --git a/tests/block/020.out b/tests/block/020.out
new file mode 100755 (executable)
index 0000000..dcb584d
--- /dev/null
+++ b/tests/block/020.out
@@ -0,0 +1,2 @@
+Running block/020
+Test complete