linux-kernel - Re: [PATCH] slub: make sysfs file removal asynchronous

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Date:   Tue, 20 Jun 2017 18:22:05 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH] slub: make sysfs file removal asynchronous

On Tue, 20 Jun 2017 18:00:11 -0400
Tejun Heo <tj@...nel.org> wrote:

> > > Signed-off-by: Tejun Heo <tj@...nel.org>
> > > Reported-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> > > Tested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> > > Fixes: bf5eb3de3847 ("slub: separate out sysfs_slab_release() from sysfs_slab_remove()")  
> > 
> > Do you think we should add cc:stable [4.11+]?  
> 
> I think we'd risk more by backporting it through -stable than keeping
> the bug there.  The bug is very difficult to hit.

Famous last words.

>  Writing to a slub
> sysfs file has to race against kmem_cache destruction and AFAICS all
> slub sysfs files are for debugging.

It's not that big of a change. It's simply moving the work to a work
queue. I've done bigger changes than this and backported it to stable
for similar reasons.

All it takes is for it to be hit once in a billion, and that billionth
time could be critical. 

-- Steve