libpf-tools/readahead: Fix attachment failure since v5.16 (#5086)

This PR accounts for the rename/refactor of the following functions

    __do_page_cache_readahead -> do_page_cache_ra -> page_cache_ra_order by torvalds/linux@8238287eadb2 and torvalds/linux@56a4d67c264e
    __page_cache_alloc -> filemap_alloc_folio -> filemap_alloc_folio_noprof by torvalds/linux@bb3c579e25e5 and torvalds/linux@b951aaff5035.

libbpf-tools/readahead.bpf.c

@@ -34,8 +34,8 @@ int BPF_PROG(do_page_cache_ra)
 	return 0;
 }
 
-SEC("fexit/__page_cache_alloc")
-int BPF_PROG(page_cache_alloc_ret, gfp_t gfp, struct page *ret)
+static __always_inline
+int alloc_done(struct page *page)
 {
 	u32 pid = bpf_get_current_pid_tgid();
 	u64 ts;
@@ -44,13 +44,33 @@ int BPF_PROG(page_cache_alloc_ret, gfp_t gfp, struct page *ret)
 		return 0;
 
 	ts = bpf_ktime_get_ns();
-	bpf_map_update_elem(&birth, &ret, &ts, 0);
+	bpf_map_update_elem(&birth, &page, &ts, 0);
 	__sync_fetch_and_add(&hist.unused, 1);
 	__sync_fetch_and_add(&hist.total, 1);
 
 	return 0;
 }
 
+SEC("fexit/__page_cache_alloc")
+int BPF_PROG(page_cache_alloc_ret, gfp_t gfp, struct page *ret)
+{
+	return alloc_done(ret);
+}
+
+SEC("fexit/filemap_alloc_folio")
+int BPF_PROG(filemap_alloc_folio_ret, gfp_t gfp, unsigned int order,
+	struct folio *ret)
+{
+	return alloc_done(&ret->page);
+}
+
+SEC("fexit/filemap_alloc_folio_noprof")
+int BPF_PROG(filemap_alloc_folio_noprof_ret, gfp_t gfp, unsigned int order,
+	struct folio *ret)
+{
+	return alloc_done(&ret->page);
+}
+
 SEC("fexit/do_page_cache_ra")
 int BPF_PROG(do_page_cache_ra_ret)
 {

libbpf-tools/readahead.c

@@ -80,6 +80,18 @@ static int readahead__set_attach_target(struct bpf_program *prog)
 {
 	int err;
 
+	/*
+	 * 56a4d67c264e ("mm/readahead: Switch to page_cache_ra_order") in v5.18
+	 * renamed do_page_cache_ra to page_cache_ra_order
+	 */
+	err = bpf_program__set_attach_target(prog, 0, "page_cache_ra_order");
+	if (!err)
+		return 0;
+
+	/*
+	 * 8238287eadb2 ("mm/readahead: make do_page_cache_ra take a readahead_control")
+	 * in v5.10 renamed __do_page_cache_readahead to do_page_cache_ra
+	*/
 	err = bpf_program__set_attach_target(prog, 0, "do_page_cache_ra");
 	if (!err)
 		return 0;
@@ -94,6 +106,33 @@ static int readahead__set_attach_target(struct bpf_program *prog)
 	return err;
 }
 
+static int attach_alloc_ret(struct readahead_bpf *obj)
+{
+	bpf_program__set_autoload(obj->progs.page_cache_alloc_ret, false);
+	bpf_program__set_autoload(obj->progs.filemap_alloc_folio_ret, false);
+	bpf_program__set_autoload(obj->progs.filemap_alloc_folio_noprof_ret, false);
+
+	/*
+	 * b951aaff5035 ("mm: enable page allocation tagging") in v6.10
+	 * renamed filemap_alloc_folio to filemap_alloc_folio_noprof
+	 */
+	if (fentry_can_attach("filemap_alloc_folio_noprof", NULL))
+		return bpf_program__set_autoload(obj->progs.filemap_alloc_folio_noprof_ret, true);
+
+	/*
+	 * bb3c579e25e5 ("mm/filemap: Add filemap_alloc_folio") in v5.16
+	 * changed __page_cache_alloc to be a wrapper of filemap_alloc_folio
+	 */
+	if (fentry_can_attach("filemap_alloc_folio", NULL))
+		return bpf_program__set_autoload(obj->progs.filemap_alloc_folio_ret, true);
+
+	if (fentry_can_attach("__page_cache_alloc", NULL))
+		return bpf_program__set_autoload(obj->progs.page_cache_alloc_ret, true);
+
+	fprintf(stderr, "failed to attach to alloc functions\n");
+	return -1;
+}
+
 int main(int argc, char **argv)
 {
 	static const struct argp argp = {
@@ -117,10 +156,9 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
-	/*
-	 * Starting from v5.10-rc1 (8238287), __do_page_cache_readahead has
-	 * renamed to do_page_cache_ra. So we specify the function dynamically.
-	 */
+	err = attach_alloc_ret(obj);
+	if (err)
+		goto cleanup;
 	err = readahead__set_attach_target(obj->progs.do_page_cache_ra);
 	if (err)
 		goto cleanup;