tools: fix cachestat.py with 5.15 kernel

Fix issue #3687.
The tool cachestat.py doesn't work with 5.15 kernel due to
kprobe function renaming. Adapt to the new function.
Also added a comment that static functions might
get inlined and the result may not be accurate if this happens.
More work can be done in the future to make the tool
more robust.

Signed-off-by: Yonghong Song <yhs@fb.com>

diff --git a/tools/cachestat.py b/tools/cachestat.py
index 2c09d14d6b15d50df1b70e0b86cda14cf2ea48e6..633f970bd6cbefc5e663f075b48db4bcb3d65eea 100755 (executable)
--- a/tools/cachestat.py
+++ b/tools/cachestat.py
@@ -96,7 +96,15 @@ if debug or args.ebpf:
 b = BPF(text=bpf_text)
 b.attach_kprobe(event="add_to_page_cache_lru", fn_name="do_count")
 b.attach_kprobe(event="mark_page_accessed", fn_name="do_count")
-b.attach_kprobe(event="account_page_dirtied", fn_name="do_count")
+
+# Function account_page_dirtied() is changed to folio_account_dirtied() in 5.15.
+# FIXME: Both folio_account_dirtied() and account_page_dirtied() are
+# static functions and they may be gone during compilation and this may
+# introduce some inaccuracy.
+if BPF.get_kprobe_functions(b'folio_account_dirtied'):
+    b.attach_kprobe(event="folio_account_dirtied", fn_name="do_count")
+elif BPF.get_kprobe_functions(b'account_page_dirtied'):
+    b.attach_kprobe(event="account_page_dirtied", fn_name="do_count")
 b.attach_kprobe(event="mark_buffer_dirty", fn_name="do_count")
 
 # header