[00/13] net: simplify seq_file code

[PATCH 01/13] seq_file: Add helpers for iteration over a hlist

Some places in kernel need to iterate over a hlist in seq_file,
so provide some common helpers.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 fs/seq_file.c            |   37 ++++++++++++++++++++++++++++++++++---
 include/linux/seq_file.h |   11 +++++++++++
 2 files changed, 45 insertions(+), 3 deletions(-)

On Fri, 05 Feb 2010 09:44:45 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:

> +struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
> +{
> +	struct hlist_node *node;
> +
> +	hlist_for_each(node, head)
> +		if (pos-- == 0)
> +			return node;
> +	return NULL;
> +}
> +EXPORT_SYMBOL(seq_hlist_start);
> +
> +struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
> +{
> +	if (!pos)
> +		return SEQ_START_TOKEN;
> +
> +	return seq_hlist_start(head, pos - 1);
> +}
> +EXPORT_SYMBOL(seq_hlist_start_head);
> +
> +struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
> +				  loff_t *ppos)
> +{
> +	struct hlist_node *node = v;
> +
> +	++*ppos;
> +	if (v == SEQ_START_TOKEN)
> +		return head->first;
> +	else
> +		return node->next;
> +}
> +EXPORT_SYMBOL(seq_hlist_next);

Oy.  Most of the global functions in seq_file.c are kerneldocumented,
as they should be!

Shouldn't seq_hlist_start_head() have been called seq_hlist_prev()?

Should seq_hlist_start() be passed *ppos, and update *ppos so the
caller can then call seq_hlist_next() and seq_hlist_prev()?

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Andrew Morton wrote:
> On Fri, 05 Feb 2010 09:44:45 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:
> 
>> +struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
>> +{
>> +	struct hlist_node *node;
>> +
>> +	hlist_for_each(node, head)
>> +		if (pos-- == 0)
>> +			return node;
>> +	return NULL;
>> +}
>> +EXPORT_SYMBOL(seq_hlist_start);
>> +
>> +struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
>> +{
>> +	if (!pos)
>> +		return SEQ_START_TOKEN;
>> +
>> +	return seq_hlist_start(head, pos - 1);
>> +}
>> +EXPORT_SYMBOL(seq_hlist_start_head);
>> +
>> +struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
>> +				  loff_t *ppos)
>> +{
>> +	struct hlist_node *node = v;
>> +
>> +	++*ppos;
>> +	if (v == SEQ_START_TOKEN)
>> +		return head->first;
>> +	else
>> +		return node->next;
>> +}
>> +EXPORT_SYMBOL(seq_hlist_next);
> 
> Oy.  Most of the global functions in seq_file.c are kerneldocumented,
> as they should be!
> 

I'll add kerneldoc in v2 patchset if I have to resend, otherwise I'll
send a delta patch for this.

> Shouldn't seq_hlist_start_head() have been called seq_hlist_prev()?
> 

The list_head version has the name seq_list_start_head().

If you need to print a title in a seq_file, call seq_list_start_head()
in ->start() handler, otherwise call seq_list_start().

Those functions really need kerneldoc. ;)

> Should seq_hlist_start() be passed *ppos, and update *ppos so the
> caller can then call seq_hlist_next() and seq_hlist_prev()?
> 

No, the ->start() callback of seq_operations shouldn't update *ppos.
I fixed some bugs in ftrace debugfs files which were caused by
updating *ppos in start().

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From: Li Zefan <lizf@cn.fujitsu.com>
Date: Fri, 05 Feb 2010 10:12:56 +0800

> I'll add kerneldoc in v2 patchset if I have to resend, otherwise I'll
> send a delta patch for this.

I want you to, at a minimum, resend the first patch because you
messed up the subject line for it.

Thanks.
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