linux-kernel - Re: [PATCH 2/3] mm: cma: introduce /proc/cmainfo

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Date:	Fri, 23 Jan 2015 15:32:09 +0300
From:	Stefan Strogin <s.strogin@...tner.samsung.com>
To:	Gioh Kim <gioh.kim@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc:	Stefan Strogin <stefan.strogin@...il.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	aneesh.kumar@...ux.vnet.ibm.com,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Pintu Kumar <pintu.k@...sung.com>,
	Weijie Yang <weijie.yang@...sung.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Hui Zhu <zhuhui@...omi.com>, Minchan Kim <minchan@...nel.org>,
	Dyasly Sergey <s.dyasly@...sung.com>,
	Vyacheslav Tyrtov <v.tyrtov@...sung.com>,
	s.strogin@...tner.samsung.com
Subject: Re: [PATCH 2/3] mm: cma: introduce /proc/cmainfo

Hello Gioh,

On 31/12/14 04:14, Gioh Kim wrote:
>
> Is it ok if the information is too big?
> I'm not sure but I remember that seq_printf has 4K limitation.

Thanks for reviewing, excuse me for a long delay.

If I understand correctly it is OK, since it's written in comments for
seq_has_overflowed():
>  * seq_files have a buffer which may overflow. When this happens a larger
>  * buffer is reallocated and all the data will be printed again.
>  * The overflow state is true when m->count == m->size.
And exactly this happens in traverse().

But I think that it's not important anymore as I intent not to use
seq_files in the second version.


>
> So I made seq_operations with seq_list_start/next functions.
>
> EX)
>
> static void *debug_seq_start(struct seq_file *s, loff_t *pos)
> {
> »       mutex_lock(&debug_lock);
> »       return seq_list_start(&debug_list, *pos);
> }   
>
> static void debug_seq_stop(struct seq_file *s, void *data)
> {
> »       struct debug_header *header = data;
>
> »       if (header == NULL || &header->head_list == &debug_list) {
> »       »       seq_printf(s, "end of info");
> »       }
>
> »       mutex_unlock(&debug_lock);
> }
>
> static void *debug_seq_next(struct seq_file *s, void *data, loff_t *pos)
> {
> »       return seq_list_next(data, &debug_list, pos);
> }
>
> static int debug_seq_show(struct seq_file *sfile, void *data)
> {
> »       struct debug_header *header;
> »       char *p;
>
> »       header= list_entry(data,
> »       »       »          struct debug_header,   
> »       »       »          head_list);
>
> »       seq_printf(sfile, "print info");
> »       return 0;
> }
> static const struct seq_operations debug_seq_ops = {
> »       .start = debug_seq_start,   
> »       .next = debug_seq_next,   
> »       .stop = debug_seq_stop,   
> »       .show = debug_seq_show,   
> };

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