linux-kernel - Re: [PATCH v6 6/7] kernfs: add kernfs_need_inode

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Message-ID: <CAJfpegtQd-eYqdSee7CwOFz=uViDV4=P+BmKR_Ciryz1wEe0FQ@mail.gmail.com>
Date:   Fri, 11 Jun 2021 15:13:37 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Ian Kent <raven@...maw.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>, Eric Sandeen <sandeen@...deen.net>,
        Fox Chen <foxhlchen@...il.com>,
        Brice Goglin <brice.goglin@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Rick Lindsley <ricklind@...ux.vnet.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 6/7] kernfs: add kernfs_need_inode_refresh()

On Wed, 9 Jun 2021 at 10:52, Ian Kent <raven@...maw.net> wrote:
>
> Now the kernfs_rwsem read lock is held for kernfs_refresh_inode() and
> the i_lock taken to protect inode updates there can be some contention
> introduced when .permission() is called with concurrent path walks in
> progress.
>
> Since .permission() is called frequently during path walks it's worth
> checking if the update is actually needed before taking the lock and
> performing the update.
>
> Signed-off-by: Ian Kent <raven@...maw.net>

Reviewed-by: Miklos Szeredi <mszeredi@...hat.com>