linux-kernel - Re: [PATCH v2 5/6] debugfs: add debugfs_create_atomic64_t for atomic64

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Message-ID: <ZC2nbiarELlUVcSj@bombadil.infradead.org>
Date:   Wed, 5 Apr 2023 09:53:02 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     david@...hat.com, patches@...ts.linux.dev,
        linux-modules@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com,
        petr.pavlu@...e.com, prarit@...hat.com, gregkh@...uxfoundation.org,
        rafael@...nel.org, christophe.leroy@...roup.eu, tglx@...utronix.de,
        peterz@...radead.org, song@...nel.org, rppt@...nel.org,
        dave@...olabs.net, willy@...radead.org, vbabka@...e.cz,
        mhocko@...e.com, dave.hansen@...ux.intel.com,
        colin.i.king@...il.com, jim.cromie@...il.com,
        catalin.marinas@....com, jbaron@...mai.com,
        rick.p.edgecombe@...el.com
Subject: Re: [PATCH v2 5/6] debugfs: add debugfs_create_atomic64_t for
 atomic64_t

On Wed, Apr 05, 2023 at 09:23:09AM -0700, Linus Torvalds wrote:
> On Wed, Apr 5, 2023 at 9:11 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
> >
> > Oh but I don't get the atomic incs, so we'd need debugfs_create_atomic_long_t().
> 
>   debugfs_create_ulong("total_mod_size",
>        0400, mod_debugfs_root,
>        &total_mod_size.counter);
> 
> but I didn't actually try to compile that kind of version.
> 
> (I think "counter" is actually a _signed_ long, so maybe the types don't match).

I see yes, sadly we'd have to cast to (unsigned long *) to make that
work as atomic_long counters are long long int:

   debugfs_create_ulong("total_mod_size",
        0400, mod_debugfs_root,
-        &total_mod_size.counter);
+        (unsigned long *)&total_mod_size.counter);

That's:

unsigned long min bits 32
long long     min bits 64

But since we'd be doing our accounting in atomic_long and just use
debugfs for prints I think that's fine. Just a bit ugly.

  Luis