linux-kernel - Re: [PATCH] fs/namespace: handle mount(MS_BIND|MS_REMOUNT) without locking sb->s

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Message-ID: <20200318144628.GI22433@bombadil.infradead.org>
Date:   Wed, 18 Mar 2020 07:46:28 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-fsdevel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
Subject: Re: [PATCH] fs/namespace: handle mount(MS_BIND|MS_REMOUNT) without
 locking sb->s_umount

On Wed, Mar 18, 2020 at 05:17:55PM +0300, Konstantin Khlebnikov wrote:
> @@ -459,11 +459,11 @@ void mnt_drop_write_file(struct file *file)
>  }
>  EXPORT_SYMBOL(mnt_drop_write_file);
>  
> +/* mount_lock must be held */
>  static int mnt_make_readonly(struct mount *mnt)
>  {
>  	int ret = 0;
>  
> -	lock_mount_hash();

I'd rather see
+	lockdep_assert_held_write(&mount_lock);
than a comment.  Maybe wrapped up into a macro like assert_hash_locked().