bcc/tools-readahead-Fix-Failed-to-attach-BPF-program-ent.patch

From c5152f68588d2195295e66daccff2126de1c35cf Mon Sep 17 00:00:00 2001
From: Rong Tao <rongtao@cestc.cn>
Date: Mon, 30 Jan 2023 17:39:35 +0800
Subject: [PATCH] tools/readahead: Fix: Failed to attach BPF program
 entry__do_page_cache_readahead

since commit 56a4d67c264e("mm/readahead: Switch to page_cache_ra_order") switch
do_page_cache_ra() to page_cache_ra_order() (v5.17), and commit bb3c579e25e5
("mm/filemap: Add filemap_alloc_folio") swap __page_cache_alloc() to
filemap_alloc_folio() (since v5.15)

Reprocude the error(fedora37, 6.1.7-200.fc37.aarch64):

    $ sudo ./readahead.py
    cannot attach kprobe, probe entry may not exist
    Traceback (most recent call last):
    File "/home/rongtao/Git/bcc/tools/./readahead.py", line 159, in <module>
        b.attach_kprobe(event=ra_event, fn_name="entry__do_page_cache_readahead")
    File "/usr/lib/python3.11/site-packages/bcc/__init__.py", line 840, in attach_kprobe
        raise Exception("Failed to attach BPF program %s to kprobe %s" %
    Exception: Failed to attach BPF program b'entry__do_page_cache_readahead' to kprobe b'do_page_cache_ra'

Signed-off-by: Rong Tao <rongtao@cestc.cn>
---
 tools/readahead.py | 69 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 56 insertions(+), 13 deletions(-)

diff --git a/tools/readahead.py b/tools/readahead.py
index f2afdcb3..adad2ea8 100755
--- a/tools/readahead.py
+++ b/tools/readahead.py
@@ -12,6 +12,7 @@
 #
 # 20-Aug-2020   Suchakra Sharma     Ported from bpftrace to BCC
 # 17-Sep-2021   Hengqi Chen         Migrated to kfunc
+# 30-Jan-2023   Rong Tao            Support more kfunc/kprobe, introduce folio
 
 from __future__ import print_function
 from bcc import BPF
@@ -38,6 +39,7 @@ args = parser.parse_args()
 bpf_text = """
 #include <uapi/linux/ptrace.h>
 #include <linux/mm_types.h>
+#include <linux/mm.h>
 
 BPF_HASH(flag, u32, u8);            // used to track if we are in do_page_cache_readahead()
 BPF_HASH(birth, struct page*, u64); // used to track timestamps of cache alloc'ed page
@@ -65,7 +67,7 @@ int exit__do_page_cache_readahead(struct pt_regs *ctx) {
 int exit__page_cache_alloc(struct pt_regs *ctx) {
     u32 pid;
     u64 ts;
-    struct page *retval = (struct page*) PT_REGS_RC(ctx);
+    struct page *retval = (struct page*) GET_RETVAL_PAGE;
     u32 zero = 0; // static key for accessing pages[0]
     pid = bpf_get_current_pid_tgid();
     u8 *f = flag.lookup(&pid);
@@ -111,6 +113,23 @@ KRETFUNC_PROBE(RA_FUNC)
     return 0;
 }
 
+KFUNC_PROBE(mark_page_accessed, struct page *arg0)
+{
+    u64 ts, delta;
+    u32 zero = 0; // static key for accessing pages[0]
+    u64 *bts = birth.lookup(&arg0);
+
+    if (bts != NULL) {
+        delta = bpf_ktime_get_ns() - *bts;
+        dist.atomic_increment(bpf_log2l(delta/1000000));
+        pages.atomic_increment(zero, -1);
+        birth.delete(&arg0); // remove the entry from hashmap
+    }
+    return 0;
+}
+"""
+
+bpf_text_kfunc_cache_alloc_ret_page = """
 KRETFUNC_PROBE(__page_cache_alloc, gfp_t gfp, struct page *retval)
 {
     u64 ts;
@@ -125,18 +144,22 @@ KRETFUNC_PROBE(__page_cache_alloc, gfp_t gfp, struct page *retval)
     }
     return 0;
 }
+"""
 
-KFUNC_PROBE(mark_page_accessed, struct page *arg0)
+bpf_text_kfunc_cache_alloc_ret_folio = """
+KRETFUNC_PROBE(filemap_alloc_folio, gfp_t gfp, unsigned int order,
+    struct folio *retval)
 {
-    u64 ts, delta;
+    u64 ts;
     u32 zero = 0; // static key for accessing pages[0]
-    u64 *bts = birth.lookup(&arg0);
+    u32 pid = bpf_get_current_pid_tgid();
+    u8 *f = flag.lookup(&pid);
+    struct page *page = folio_page(retval, 0);
 
-    if (bts != NULL) {
-        delta = bpf_ktime_get_ns() - *bts;
-        dist.atomic_increment(bpf_log2l(delta/1000000));
-        pages.atomic_increment(zero, -1);
-        birth.delete(&arg0); // remove the entry from hashmap
+    if (f != NULL && *f == 1) {
+        ts = bpf_ktime_get_ns();
+        birth.update(&page, &ts);
+        pages.atomic_increment(zero);
     }
     return 0;
 }
@@ -145,20 +168,40 @@ KFUNC_PROBE(mark_page_accessed, struct page *arg0)
 if BPF.support_kfunc():
     if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
         ra_func = "__do_page_cache_readahead"
-    else:
+    elif BPF.get_kprobe_functions(b"do_page_cache_ra"):
         ra_func = "do_page_cache_ra"
+    elif BPF.get_kprobe_functions(b"page_cache_ra_order"):
+        ra_func = "page_cache_ra_order"
+    else:
+        print("Not found any kfunc.")
+        exit()
     bpf_text += bpf_text_kfunc.replace("RA_FUNC", ra_func)
+    if BPF.get_kprobe_functions(b"__page_cache_alloc"):
+        bpf_text += bpf_text_kfunc_cache_alloc_ret_page
+    else:
+        bpf_text += bpf_text_kfunc_cache_alloc_ret_folio
     b = BPF(text=bpf_text)
 else:
     bpf_text += bpf_text_kprobe
-    b = BPF(text=bpf_text)
     if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
         ra_event = "__do_page_cache_readahead"
-    else:
+    elif BPF.get_kprobe_functions(b"do_page_cache_ra"):
         ra_event = "do_page_cache_ra"
+    elif BPF.get_kprobe_functions(b"page_cache_ra_order"):
+        ra_event = "page_cache_ra_order"
+    else:
+        print("Not found any kprobe.")
+        exit()
+    if BPF.get_kprobe_functions(b"__page_cache_alloc"):
+        cache_func = "__page_cache_alloc"
+        bpf_text = bpf_text.replace('GET_RETVAL_PAGE', 'PT_REGS_RC(ctx)')
+    else:
+        cache_func = "filemap_alloc_folio"
+        bpf_text = bpf_text.replace('GET_RETVAL_PAGE', 'folio_page((struct folio *)PT_REGS_RC(ctx), 0)')
+    b = BPF(text=bpf_text)
     b.attach_kprobe(event=ra_event, fn_name="entry__do_page_cache_readahead")
     b.attach_kretprobe(event=ra_event, fn_name="exit__do_page_cache_readahead")
-    b.attach_kretprobe(event="__page_cache_alloc", fn_name="exit__page_cache_alloc")
+    b.attach_kretprobe(event=cache_func, fn_name="exit__page_cache_alloc")
     b.attach_kprobe(event="mark_page_accessed", fn_name="entry_mark_page_accessed")
 
 # header
-- 
2.39.1