linux-kernel - Re: [PATCH v2 2/2] fs: super.c: Add tracepoint to get name of superblock shrinker

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Message-ID: <20160818064001.GB30162@dhcp22.suse.cz>
Date:	Thu, 18 Aug 2016 08:40:02 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Janani Ravichandran <janani.rvchndrn@...il.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, riel@...riel.com,
	akpm@...ux-foundation.org, vdavydov@...tuozzo.com, vbabka@...e.cz,
	mgorman@...hsingularity.net, kirill.shutemov@...ux.intel.com,
	bywxiaobai@....com
Subject: Re: [PATCH v2 2/2] fs: super.c: Add tracepoint to get name of
 superblock shrinker

On Thu 18-08-16 07:32:39, Al Viro wrote:
> On Thu, Aug 18, 2016 at 02:09:31AM -0400, Janani Ravichandran wrote:
> 
> >  static LIST_HEAD(super_blocks);
> > @@ -64,6 +65,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
> >  	long	inodes;
> >  
> >  	sb = container_of(shrink, struct super_block, s_shrink);
> > +	trace_mm_shrinker_callback(shrink, sb->s_type->name);
> 
> IOW, we are (should that patch be accepted) obliged to keep the function in
> question and the guts of struct shrinker indefinitely.

I am not aware that trace points are considered a stable ABI. Is that
documented anywhere? We have changed/removed some of them in the
past. If there is a debugging tool parsing them the tool itself is
responsible to keep track of any changes.
-- 
Michal Hocko
SUSE Labs