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From: Matthew Wilcox <willy@infradead.org>
To: Zqiang <qiang.zhang1211@gmail.com>
Cc: akpm@linux-foundation.org, sunhao.th@gmail.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm: backing-dev: use kfree_rcu() instead of synchronize_rcu_expedited()
Date: Thu, 14 Oct 2021 12:24:22 +0100	[thread overview]
Message-ID: <YWgTZjDtZik/9l4J@casper.infradead.org> (raw)
In-Reply-To: <20211014082433.30733-1-qiang.zhang1211@gmail.com>

On Thu, Oct 14, 2021 at 04:24:33PM +0800, Zqiang wrote:
> The bdi_remove_from_list() is called in RCU softirq, however the
> synchronize_rcu_expedited() will produce sleep action, use kfree_rcu()
> instead of it.
> 
> Reported-by: Hao Sun <sunhao.th@gmail.com>
> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
> ---
>  include/linux/backing-dev-defs.h | 1 +
>  mm/backing-dev.c                 | 4 +---
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
> index 33207004cfde..35a093384518 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -202,6 +202,7 @@ struct backing_dev_info {
>  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *debug_dir;
>  #endif
> +	struct rcu_head rcu;
>  };

Instead of growing struct backing_dev_info, it seems to me this rcu_head
could be placed in a union with rb_node, since it will have been removed
from the bdi_tree by this point and the tree is never walked under
RCU protection?


  reply	other threads:[~2021-10-14 11:26 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-14  8:24 [PATCH] mm: backing-dev: use kfree_rcu() instead of synchronize_rcu_expedited() Zqiang
2021-10-14 11:24 ` Matthew Wilcox [this message]
2021-10-15  3:39   ` zhangqiang
     [not found]   ` <CALm+0cUt7iD5zex4-hRv=i1wPd66tz3JYGHz8P8ZFTZcyOCD1A@mail.gmail.com>
     [not found]     ` <d697d61e-27a2-a25c-3ae1-e41457d08705@gmail.com>
2021-10-15 12:35       ` Matthew Wilcox
2021-10-15 13:19         ` Christoph Hellwig
2021-10-18  2:15         ` Zqiang
2021-10-14 12:06 ` Christoph Hellwig

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