linux-kernel - Re: [PATCH 2/2] md: Remove extra mddev_get() in md_seq

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Date:   Tue, 6 Sep 2022 14:06:51 +0800
From:   Guoqing Jiang <guoqing.jiang@...ux.dev>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Song Liu <song@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>
Subject: Re: [PATCH 2/2] md: Remove extra mddev_get() in md_seq_start()



On 9/3/22 1:16 AM, Logan Gunthorpe wrote:
> A regression is seen where mddev devices stay permanently after they
> are stopped due to an elevated reference count.
>
> This was tracked down to an extra mddev_get() in md_seq_start().
>
> It only happened rarely because most of the time the md_seq_start()
> is called with a zero offset. The path with an extra mddev_get() only
> happens when it starts with a non-zero offset.
>
> The commit noted below changed an mddev_get() to check its success
> but inadevrtantly left the original call in. Remove the extra call.
>
> Fixes: 12a6caf27324 ("md: only delete entries from all_mddevs when the disk is freed")
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> ---
>   drivers/md/md.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index afaf36b2f6ab..9dc0175280b4 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8154,7 +8154,6 @@ static void *md_seq_start(struct seq_file *seq, loff_t *pos)
>   	list_for_each(tmp,&all_mddevs)
>   		if (!l--) {
>   			mddev = list_entry(tmp, struct mddev, all_mddevs);
> -			mddev_get(mddev);
>   			if (!mddev_get(mddev))
>   				continue;
>   			spin_unlock(&all_mddevs_lock);

Acked-by: Guoqing Jiang <Guoqing.jiang@...ux.dev>

Thanks,
Guoqing