Re: [PATCH net-next v2 5/7] selftests: rds: Fix gcov and pcap collection

[Jakub Kicinski <kuba@kernel.org>]

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---
selftests: rds: Fix gcov and pcap collection

This commit addresses dependencies on host systemd configurations in the vng
guest. It adds mounts for tmpfs on /tmp and debugfs to ensure pcap and gcov
data collection work, and updates the gcovr root path.

> diff --git a/tools/testing/selftests/net/rds/run.sh b/tools/testing/selftests/net/rds/run.sh
> index bc2e53126aab..3fc116d23410 100755
> --- a/tools/testing/selftests/net/rds/run.sh
> +++ b/tools/testing/selftests/net/rds/run.sh
> @@ -197,6 +197,13 @@ COVR_DIR="${LOG_DIR}/coverage/"
>  mkdir -p  "$LOG_DIR"
>  mkdir -p "$COVR_DIR"
>  
> +# tcpdump saves pcaps to /tmp because it requires chown to save the
> +# pcap but chown is not supported by 9p.  Mount tmpfs on /tmp if it is
> +# not already a separate filesystem
> +if ! mountpoint -q /tmp 2>/dev/null; then
> +	mount -t tmpfs tmpfs /tmp
> +fi
> +

Could this introduce a regression when the test is run directly on a host
workstation rather than inside an isolated VM?

If /tmp is a regular directory on the root filesystem, mounting tmpfs over it
will instantly hide all existing files and UNIX domain sockets in /tmp.

Since there is no cleanup trap to unmount it on exit or failure, does this
leave the host system in a degraded state?

[ ... ]

>  if [ "$GENERATE_GCOV_REPORT" -eq 1 ]; then
>         echo saving coverage data...
> +
> +       # Ensure debugfs is mounted
> +       if ! test -d /sys/kernel/debug/gcov; then
> +               mount -t debugfs debugfs /sys/kernel/debug 2>/dev/null || true
> +       fi
> +

If the test is run against a kernel that does not have CONFIG_GCOV_KERNEL
enabled, the gcov directory will not exist even when debugfs is correctly
mounted.

Will this condition cause a regression where the script repeatedly mounts
debugfs on every run, stacking redundant shadow mounts over
/sys/kernel/debug since they are never unmounted?
-- 
pw-bot: cr