generic/778: fix background loop control with sentinel files
This test fails on my slowish QA VM with 32k-fsblock xfs:
--- /run/fstests/bin/tests/generic/778.out 2025-10-20 10:03:43.432910446 -0700
+++ /var/tmp/fstests/generic/778.out.bad 2025-11-04 12:01:31.137813652 -0800
@@ -1,2 +1,137 @@
QA output created by 778
-Silence is golden
+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/778.full for details)
Injecting a 'ps auxfww' into the _scratch_cycle_mount helper reveals
that this process is still sitting on /opt:
root 1804418 9.0 0.8 144960 134368 pts/0 Dl+ 12:01 0:00 /run/fstests/xfsprogs/io/xfs_io -i -c open -fsd /opt/testfile -c pwrite -S 0x61 -DA -V1 -b 134217728 134217728 134217728
Yes, that's the xfs_io process started by atomic_write_loop.
Inexplicably, the awloop killing code terminates the subshell running
the for loop in atomic_write_loop but only waits for the subshell itself
to exit. It doesn't wait for any of that subshell's children, and
that's why the unmount fails.
A bare "wait" (without the $awloop_pid parameter) also doesn't wait for
the xfs_io because the parent shell sees the subshell exit and treats
that as job completion. We can't use killall here because the system
could be running check-parallel, nor can we use pkill here because the
pid namespace containment code was removed.
The simplest stupid answer is to use sentinel files to control the loop.
Cc: [email protected] # v2025.10.20
Fixes: ca954527ff9d97 ("generic: Add sudden shutdown tests for multi block atomic writes")
Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Ojaswin Mujoo <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Zorro Lang <[email protected]>
1 file changed
