From: Jens Axboe <axboe@kernel.dk>
To: Mateusz Guzik <mjguzik@gmail.com>,
brauner@kernel.org, viro@zeniv.linux.org.uk
Cc: jack@suse.cz, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org,
audit@vger.kernel.org
Subject: Re: [PATCH] fs: dodge an atomic in putname if ref == 1
Date: Wed, 12 Mar 2025 10:07:21 -0600 [thread overview]
Message-ID: <6115bfac-658c-4e8c-859f-d4a1a5820dae@kernel.dk> (raw)
In-Reply-To: <20250311181804.1165758-1-mjguzik@gmail.com>
On 3/11/25 12:18 PM, Mateusz Guzik wrote:
> diff --git a/fs/namei.c b/fs/namei.c
> index 06765d320e7e..add90981cfcd 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -275,14 +275,19 @@ EXPORT_SYMBOL(getname_kernel);
>
> void putname(struct filename *name)
> {
> + int refcnt;
> +
> if (IS_ERR_OR_NULL(name))
> return;
>
> - if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
> - return;
> + refcnt = atomic_read(&name->refcnt);
> + if (refcnt != 1) {
> + if (WARN_ON_ONCE(!refcnt))
> + return;
>
> - if (!atomic_dec_and_test(&name->refcnt))
> - return;
> + if (!atomic_dec_and_test(&name->refcnt))
> + return;
> + }
Looks good to me, I use this trick with bitops too all the time, to
avoid a RMW when possible.
Reviewed-by: Jens Axboe <axboe@kernel.dk>
--
Jens Axboe
prev parent reply other threads:[~2025-03-12 16:07 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-11 18:18 [PATCH] fs: dodge an atomic in putname if ref == 1 Mateusz Guzik
2025-03-12 8:36 ` Christian Brauner
2025-03-12 15:51 ` Jan Kara
2025-03-12 16:07 ` Jens Axboe [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6115bfac-658c-4e8c-859f-d4a1a5820dae@kernel.dk \
--to=axboe@kernel.dk \
--cc=audit@vger.kernel.org \
--cc=brauner@kernel.org \
--cc=io-uring@vger.kernel.org \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mjguzik@gmail.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox