Re: [PATCH] perf test probe_vfs_getname: Correct probe line for updated kernel code

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Fri, May 16, 2025 at 10:05:32AM +0100, Leo Yan wrote:
> Since commit 611851010c74 ("fs: dedup handling of struct filename init
> and refcounts bumps"), the kernel has been refactored to use a new
> inline function initname(), moving name initialization into it.
> 
> As a result, the perf probe test can no longer find the source line that
> matches the defined regular expressions.  This causes the script to fail
> when attempting to add probes.
> 
> Update the regular expression to search for the call site of initname().

Well, I'd say we should add, not update, i.e. a new perf should continue
to work on an older kernel, so please consider the following patch.

- Arnaldo

diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
index 89f72a4c818c712b..aa867e28eadc46bc 100644
--- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
+++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
@@ -13,8 +13,17 @@ cleanup_probe_vfs_getname() {
 add_probe_vfs_getname() {
 	add_probe_verbose=$1
 	if [ $had_vfs_getname -eq 1 ] ; then
-		result_filename_re="[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*"
-		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_filename_re" | sed -r "s/$result_filename_re/\1/")
+		# Please keep the older regexps so that this will pass on older kernels as well
+		# as in the most recent one.
+
+		result_initname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname.*"
+		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_initname_re" | sed -r "s/$result_initname_re/\1/")
+
+		if [ -z "$line" ] ; then
+			result_filename_re="[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*"
+			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_filename_re" | sed -r "s/$result_filename_re/\1/")
+		fi
+
 		if [ -z "$line" ] ; then
 			result_aname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+result->aname = NULL;"
 			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_aname_re" | sed -r "s/$result_aname_re/\1/")

> This provides a valid source line number for adding the probe.
> 
> Fixes: 611851010c74 ("fs: dedup handling of struct filename init and refcounts bumps")
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
>  tools/perf/tests/shell/lib/probe_vfs_getname.sh | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> index 89f72a4c818c..cbfdd2a62c6e 100644
> --- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> +++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
> @@ -13,12 +13,8 @@ cleanup_probe_vfs_getname() {
>  add_probe_vfs_getname() {
>  	add_probe_verbose=$1
>  	if [ $had_vfs_getname -eq 1 ] ; then
> -		result_filename_re="[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*"
> -		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_filename_re" | sed -r "s/$result_filename_re/\1/")
> -		if [ -z "$line" ] ; then
> -			result_aname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+result->aname = NULL;"
> -			line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_aname_re" | sed -r "s/$result_aname_re/\1/")
> -		fi
> +		result_initname_re="[[:space:]]+([[:digit:]]+)[[:space:]]+initname.*"
> +		line=$(perf probe -L getname_flags 2>&1 | grep -E "$result_initname_re" | sed -r "s/$result_initname_re/\1/")
>  
>  		if [ -z "$line" ] ; then
>  			echo "Could not find probeable line"
> -- 
> 2.34.1