linux-kernel - Re: [PATCH v2 5/6] super: use common iterator (Part 2)

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Message-ID: <mmzfke3c6ioply3ezhushtoxnca5e3kx3ynteie6sf7cye3bqm@yu7wpqctwbrb>
Date: Mon, 31 Mar 2025 12:07:12 +0200
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, jack@...e.cz, 
	linux-kernel@...r.kernel.org, James Bottomley <James.Bottomley@...senpartnership.com>, 
	mcgrof@...nel.org, hch@...radead.org, david@...morbit.com, rafael@...nel.org, 
	djwong@...nel.org, pavel@...nel.org, peterz@...radead.org, mingo@...hat.com, 
	will@...nel.org, boqun.feng@...il.com
Subject: Re: [PATCH v2 5/6] super: use common iterator (Part 2)

On Sat 29-03-25 09:42:18, Christian Brauner wrote:
> Use a common iterator for all callbacks. We could go for something even
> more elaborate (advance step-by-step similar to iov_iter) but I really
> don't think this is warranted.
> 
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Looks good, one nit below. With that fixed feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

> +#define invalid_super list_entry_is_head

Why do you have this invalid_super define? I find it rather confusing in
the loop below and list_entry_is_head() would be much more
understandable...

								Honza

> +
> +static void __iterate_supers(void (*f)(struct super_block *, void *), void *arg,
> +			     enum super_iter_flags_t flags)
>  {
>  	struct super_block *sb, *p = NULL;
> +	bool excl = flags & SUPER_ITER_EXCL;
>  
> -	spin_lock(&sb_lock);
> -	list_for_each_entry(sb, &super_blocks, s_list) {
> -		bool locked;
> +	guard(spinlock)(&sb_lock);
>  
> +	for (sb = first_super(flags); !invalid_super(sb, &super_blocks, s_list);
> +	     sb = next_super(sb, flags)) {
>  		if (super_flags(sb, SB_DYING))
>  			continue;
>  		sb->s_count++;
>  		spin_unlock(&sb_lock);
>  
> -		locked = super_lock(sb, excl);
> -		if (locked) {
> +		if (flags & SUPER_ITER_UNLOCKED) {
> +			f(sb, arg);
> +		} else if (super_lock(sb, excl)) {
>  			f(sb, arg);
>  			super_unlock(sb, excl);
>  		}
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR