linux-kernel - Re: [PATCH 04/21] fs: Implement lazy LRU updates for inodes

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Date:	Thu, 21 Oct 2010 21:07:06 +1100
From:	Nick Piggin <npiggin@...nel.dk>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/21] fs: Implement lazy LRU updates for inodes

On Thu, Oct 21, 2010 at 11:49:29AM +1100, Dave Chinner wrote:
>  		} else {
>  			/*
> -			 * The inode is clean, unused
> +			 * The inode is clean. If it is unused, then make sure
> +			 * that it is put on the LRU correctly as iput_final()
> +			 * does not move dirty inodes to the LRU and dirty
> +			 * inodes are removed from the LRU during scanning.
>  			 */
> -			list_move(&inode->i_list, &inode_unused);
> +			list_del_init(&inode->i_list);
> +			if (!atomic_read(&inode->i_count))
> +				inode_lru_list_add(inode);

This "optimisation" is surely wrong. How could we have no reference
on the inode at this point?


> -static int can_unuse(struct inode *inode)
> -{
> -	if (inode->i_state)
> -		return 0;
> -	if (inode_has_buffers(inode))
> -		return 0;
> -	if (atomic_read(&inode->i_count))
> -		return 0;
> -	if (inode->i_data.nrpages)
> -		return 0;
> -	return 1;
> -}

Avoiding the reclaim optimisation? As I said, I noticed some increased
scanning in heavy reclaim from removing this.

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