linux-kernel - Re: The bug of iput() removal from flusher thread?

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Message-ID: <20121120223741.GI2591@dastard>
Date:	Wed, 21 Nov 2012 09:37:41 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Jan Kara <jack@...e.cz>
Cc:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: The bug of iput() removal from flusher thread?

On Mon, Nov 19, 2012 at 08:41:02PM +0100, Jan Kara wrote:
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 51ea267..ed7613b 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -227,6 +227,9 @@ static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
>  
>  static void inode_sync_complete(struct inode *inode)
>  {
> +	/* If inode is clean an unused, put it into LRU now.  */
> +	if (!(inode->i_state & I_DIRTY) && !atomic_read(&inode->i_count))
> +		inode_lru_list_add(inode);

Unsafe. Has to avoid I_FREEING|I_WILL_FREE (see warnings at start of
writeback_single_inode()).

Also, if you do this after clearing the I_SYNC flag, you can use
exactly the same logic as iput_final(). A helper function could be
used for both cases at that point, and....

> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -397,7 +397,7 @@ void ihold(struct inode *inode)
>  }
>  EXPORT_SYMBOL(ihold);
>  
> -static void inode_lru_list_add(struct inode *inode)
> +void inode_lru_list_add(struct inode *inode)

.... the inode lru list function can stay static.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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