linux-kernel - Re: [PATCH v2 3/3] vfs: Use per-cpu list for superblock's inode list

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Message-ID: <56CCAB61.20206@hpe.com>
Date:	Tue, 23 Feb 2016 13:56:33 -0500
From:	Waiman Long <waiman.long@....com>
To:	Dave Chinner <david@...morbit.com>
CC:	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.com>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Chinner <dchinner@...hat.com>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH v2 3/3] vfs: Use per-cpu list for superblock's inode list

On 02/21/2016 04:34 PM, Dave Chinner wrote:
> On Fri, Feb 19, 2016 at 04:10:45PM -0500, Waiman Long wrote:
>> +/*
>> + * Superblock's inode list iterator function and arguments macros
>> + */
>> +#define SB_INODES_ITER_FUNC(name, lock, struct_fields)			\
>> +	struct name ## _arg {						\
>> +		struct_fields;						\
>> +	};								\
>> +	static int name ## _iter(struct pcpu_list_node *_node,		\
>> +				 struct pcpu_list_node **_pnext,	\
>> +				 spinlock_t *lock, void *_arg)
>> +
>> +#define SB_INODES_ITER_ARGS(name, i, a)					\
>> +	struct inode *i = container_of(_node, struct inode, i_sb_list);	\
>> +	struct name ## _arg *a = (struct name ## _arg *)_arg
>> +
>> +#define SB_INODES_ITER_ARGS_SAFE(name, i, n, a)				\
>> +	struct inode *i = container_of(_node, struct inode, i_sb_list);	\
>> +	struct inode *n = container_of(*_pnext, struct inode, i_sb_list);\
>> +	struct name ## _arg *a = (struct name ## _arg *)_arg
>> +
>> +#define SB_INODES_ITER_SET_PCPU_LIST_NEXT(n)				\
>> +	{ *_pnext =&(n)->i_sb_list; }
>> +
>> +#define SB_INODES_ITER_CALL(name, sb)					\
>> +	pcpu_list_iterate(sb->s_inodes, false, NULL, name ## _iter,&arg)
>> +
>> +#define SB_INODES_ITER_CALL_SAFE(name, sb, phead)			\
>> +	pcpu_list_iterate(sb->s_inodes, true, phead, name ## _iter,&arg)
>> +
> No, just no.
>
> Ungreppable, breaks cscope, obfuscates everything, shouts a lot,
> code using the API looks completely broken (e.g. semi-colons in
> "function declarations"), and it reminds me of the worst of the
> worst unmaintainable code in an exceedingly buggy and undebuggable
> proprietary filesystem I've previously had the "joy" of working
> with.
>
> Just fix the bug in the previous version; it's so much cleaner than
> this .... mess.
>
> Cheers,
>
> Dave.

Sorry for that. I will scrap the current approach and use another way to 
iterate the list instead. I will send out an updated patch soon.

Cheers,
Longman