Re: [PATCH 05/11] vmscan: don't bother with debugfs_real_fops()

[Al Viro <viro@zeniv.linux.org.uk>]

On Thu, Jul 03, 2025 at 12:51:57PM +0100, Matthew Wilcox wrote:
> On Wed, Jul 02, 2025 at 10:17:39PM +0100, Al Viro wrote:
> > -	bool full = !debugfs_real_fops(m->file)->write;
> > +	bool full = debugfs_get_aux_num(m->file);
> 
> > +	debugfs_create_file_aux_num("lru_gen", 0644, NULL, NULL, 1,
> > +				    &lru_gen_rw_fops);
> > +	debugfs_create_file_aux_num("lru_gen_full", 0444, NULL, NULL, 0,
> > +				    &lru_gen_ro_fops);
> 
> Looks like you have the polarity inverted there?

Right you are.  My apologies...  Fixed, force-pushed into the same branch,
replacement commit below:

From 51d26db0fd00fbd501f9271550667bab6c5fb107 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Wed, 29 Jan 2025 14:43:44 -0500
Subject: [PATCH 05/11] vmscan: don't bother with debugfs_real_fops()

... not when it's used only to check which file is used;
debugfs_create_file_aux_num() allows to stash a number into
debugfs entry and debugfs_get_aux_num() extracts it.

Braino-spotted-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 mm/vmscan.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f8dfd2864bbf..27c70848c0a0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5420,7 +5420,7 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec,
 static int lru_gen_seq_show(struct seq_file *m, void *v)
 {
 	unsigned long seq;
-	bool full = !debugfs_real_fops(m->file)->write;
+	bool full = debugfs_get_aux_num(m->file);
 	struct lruvec *lruvec = v;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	int nid = lruvec_pgdat(lruvec)->node_id;
@@ -5756,8 +5756,10 @@ static int __init init_lru_gen(void)
 	if (sysfs_create_group(mm_kobj, &lru_gen_attr_group))
 		pr_err("lru_gen: failed to create sysfs group\n");
 
-	debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops);
-	debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops);
+	debugfs_create_file_aux_num("lru_gen", 0644, NULL, NULL, false,
+				    &lru_gen_rw_fops);
+	debugfs_create_file_aux_num("lru_gen_full", 0444, NULL, NULL, true,
+				    &lru_gen_ro_fops);
 
 	return 0;
 };
-- 
2.39.5