linux-kernel - Re: [RFC PATCH] mm: trace filemap add and del

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Message-ID: <87vccx500r.fsf@free.fr>
Date:	Thu, 22 Nov 2012 12:51:00 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Dave Chinner <david@...morbit.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm: trace filemap add and del

Dave Chinner <david@...morbit.com> writes:

> We actually have an informal convention for formating filesystem
> trace events, and that is to use the device number....
>
>> 
>> > +	),
>> > +
>> > +	TP_printk("page=%p pfn=%lu blk=%d:%d inode+ofs=%lu+%lu",
>
> ... and to prefix messages like:
>
> 	TP_printk("dev %d:%d ino 0x%llx ....
> 		  MAJOR(__entry->dev), MINOR(__entry->dev),
>
> i.e. the start of the event message has all the identifying
> information where it is easy to grep for and get all the events for
> a specific dev/inode combination without even having to think about
> it.

I cross-checked your proposition.
The "ino 0x%llx" looks wrong to me, because :
 - i_ino is "unsigned long", not "(unsigned) long long"

 - triggers a printk where "ino" looks really awfull (on a 32bits LE arm)
>  mm_filemap_add_to_page_cache: dev 0:2 ino 0xc05186e000000000 page=000a0737
>  pfn=0 ofs=3283861504

 - why print the inode number in hexadecimal format ???
   Doing a "ls -i" returns decimal format, "debugfs" returns decimal. What is
   the rational behind hexadecimal ?

I'd rather have : "dev %d:%d ino %lu page=0x%p pfn=%lu ofs=%lu".

-- 
Robert
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