[PATCH 14/23] generic/032: fix pinned mount failure

Darrick J. Wong
2025-01-16T23:28:50Z

generic/032 now periodically fails with:

--- /tmp/fstests/tests/generic/032.out 2025-01-05 11:42:14.427388698 -0800
+++ /var/tmp/fstests/generic/032.out.bad 2025-01-06 18:20:17.122818195 -0800
@@ -1,5 +1,7 @@
QA output created by 032
100 iterations
-000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd >................<
-*
-100000
+umount: /opt: target is busy.
+mount: /opt: /dev/sda4 already mounted on /opt.
+ dmesg(1) may have more information after failed mount system call.
+cycle mount failed
+(see /var/tmp/fstests/generic/032.full for details)

The root cause of this regression is the _syncloop subshell. This
background process runs _scratch_sync, which is actually an xfs_io
process that calls syncfs on the scratch mount.

Unfortunately, while the test kills the _syncloop subshell, it doesn't
actually kill the xfs_io process. If the xfs_io process is in D state
running the syncfs, it won't react to the signal, but it will pin the
mount. Then the _scratch_cycle_mount fails because the mount is pinned.

Prior to commit 8973af00ec212f the _syncloop ran sync(1) which avoided
pinning the scratch filesystem.

Fix this by pgrepping for the xfs_io process and killing and waiting for
it if necessary.

Cc: <fstests@vger.kernel.org> # v2024.12.08
Fixes: 8973af00ec212f ("fstests: cleanup fsstress process management")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
common/rc | 6 ++++++
tests/generic/032 | 9 +++++++++
2 files changed, 15 insertions(+)

diff --git a/common/rc b/common/rc
index 4419cfc3188374..d7f3c48eafe590 100644
--- a/common/rc
+++ b/common/rc
@@ -36,6 +36,12 @@ _pkill()
pkill --session 0 "$@"
}

+# Find only the test processes started by this test
+_pgrep()
+{
+ pgrep --session 0 "$@"
+}
+
# Common execution handling for fsstress invocation.
#
# We need per-test fsstress binaries because of the way fsstress forks and
diff --git a/tests/generic/032 b/tests/generic/032
index 30290c7225a2fa..48d594fe9315b8 100755
--- a/tests/generic/032
+++ b/tests/generic/032
@@ -81,6 +81,15 @@ echo $iters iterations
kill $syncpid
wait

+# The xfs_io instance started by _scratch_sync could be stuck in D state when
+# the subshell running _syncloop & is killed. That xfs_io process pins the
+# mount so we must kill it and wait for it to die before cycling the mount.
+dead_syncfs_pid=$(_pgrep xfs_io)
+if [ -n "$dead_syncfs_pid" ]; then
+ _pkill xfs_io
+ wait $dead_syncfs_pid
+fi
+
# clear page cache and dump the file
_scratch_cycle_mount
_hexdump $SCRATCH_MNT/file