linux-kernel - Re: [PATCH v2] vfs: avoid dereferencing pointers in iterate

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Date:   Thu, 17 May 2018 11:26:38 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     viro@...iv.linux.org.uk, jack@...e.com,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        lurodriguez@...e.de
Subject: Re: [PATCH v2] vfs: avoid dereferencing pointers in iterate_supers
 callbacks

On Thu, May 17, 2018 at 01:43:36PM -0400, Jeff Layton wrote:
> @@ -107,12 +109,10 @@ static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
>   */
>  void ksys_sync(void)
>  {
> -	int nowait = 0, wait = 1;
> -
>  	wakeup_flusher_threads(WB_REASON_SYNC);
>  	iterate_supers(sync_inodes_one_sb, NULL);
> -	iterate_supers(sync_fs_one_sb, &nowait);
> -	iterate_supers(sync_fs_one_sb, &wait);
> +	iterate_supers(sync_fs_one_sb, NULL);
> +	iterate_supers(sync_fs_one_sb, (void *)1UL);

I think this is actually less clear.  How about:

	void *wait = (void *)1UL;

	iterate_supers(sync_fs_one_sb, !wait);
	iterate_supers(sync_fs_one_sb, wait);