Date: Wed, 30 Jun 2010 19:26:41 +1000
From: Dave Chinner <david@fromorbit.com>
To: npiggin@suse.de
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       John Stultz <johnstul@us.ibm.com>, Frank Mayhar <fmayhar@google.com>
Subject: Re: [patch 44/52] fs: icache per-CPU sb inode lists and locks
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 <20100624030732.702284052@suse.de>
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On Thu, Jun 24, 2010 at 01:02:56PM +1000, npiggin@suse.de wrote:
> Signed-off-by: Nick Piggin <npiggin@suse.de>
.....
> @@ -2194,6 +2198,58 @@ static inline void insert_inode_hash(str
>  
>  extern void file_sb_list_add(struct file *f, struct super_block *sb);
>  extern void file_sb_list_del(struct file *f);
> +#ifdef CONFIG_SMP
> +
> +/*
> + * These macros iterate all inodes on all CPUs for a given superblock.
> + * rcu_read_lock must be held.
> + */
> +#define do_inode_list_for_each_entry_rcu(__sb, __inode)		\
> +{								\
> +	int i;							\
> +	for_each_possible_cpu(i) {				\
> +		struct list_head *list;				\
> +		list = per_cpu_ptr((__sb)->s_inodes, i);	\
> +		list_for_each_entry_rcu((__inode), list, i_sb_list)
> +
> +#define while_inode_list_for_each_entry_rcu			\
> +	}							\
> +}
> +
> +#define do_inode_list_for_each_entry_safe(__sb, __inode, __tmp)	\
> +{								\
> +	int i;							\
> +	for_each_possible_cpu(i) {				\
> +		struct list_head *list;				\
> +		list = per_cpu_ptr((__sb)->s_inodes, i);	\
> +		list_for_each_entry_safe((__inode), (__tmp), list, i_sb_list)
> +
> +#define while_inode_list_for_each_entry_safe			\
> +	}							\
> +}
> +
> +#else
> +
> +#define do_inode_list_for_each_entry_rcu(__sb, __inode)		\
> +{								\
> +	struct list_head *list;					\
> +	list = &(sb)->s_inodes;					\
> +	list_for_each_entry_rcu((__inode), list, i_sb_list)
> +
> +#define while_inode_list_for_each_entry_rcu			\
> +}
> +
> +#define do_inode_list_for_each_entry_safe(__sb, __inode, __tmp)	\
> +{								\
> +	struct list_head *list;					\
> +	list = &(sb)->s_inodes;					\
> +	list_for_each_entry_rcu((__inode), (__tmp), list, i_sb_list)
> +
> +#define while_inode_list_for_each_entry_safe			\
> +}

I can't say that I'm a great fan of hiding loop context in defines
like this. It reminds far too much of how parts of Irix slowly
ossified because they ended up mess of complex, fragile macros that
nobody fully understood...

Cheers.

Dave.
-- 
Dave Chinner
david@fromorbit.com
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