linux-kernel - Re: [RFC for-next v2 2/4] bio: split pcpu cache part of bio

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Message-ID: <Y1EHH/+TBtGn2/U8@infradead.org>
Date:   Thu, 20 Oct 2022 01:30:23 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Pavel Begunkov <asml.silence@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [RFC for-next v2 2/4] bio: split pcpu cache part of bio_put into
 a helper

> +	if ((bio->bi_opf & REQ_POLLED) && !WARN_ON_ONCE(in_interrupt())) {
> +		bio->bi_next = cache->free_list;
> +		cache->free_list = bio;
> +		cache->nr++;
> +	} else {
> +		put_cpu();
> +		bio_free(bio);
> +		return;
> +	}

This reads a little strange with the return in an else.  Why not:

	if (!(bio->bi_opf & REQ_POLLED) || WARN_ON_ONCE(in_interrupt())) {
		put_cpu();
		bio_free(bio);
		return;
	}

	bio->bi_next = cache->free_list;
	cache->free_list = bio;
	cache->nr++;

but given that the simple free case doesn't care about what CPU we're
on or the per-cpu cache pointer, I think we can simply move the

	cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu());

after the above return as well.