linux-kernel - Re: [PATCH v2 sl-b 3/5] mm: Make mem_dump

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Date:   Wed, 9 Dec 2020 20:39:24 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>, paulmck@...nel.org
Cc:     paulmck@...nel.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org, iamjoonsoo.kim@....com,
        andrii@...nel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 sl-b 3/5] mm: Make mem_dump_obj() handle vmalloc()
 memory

On Wed, Dec 09, 2020 at 06:51:20PM +0100, Vlastimil Babka wrote:
> On 12/9/20 2:13 AM, paulmck@...nel.org wrote:
> > From: "Paul E. McKenney" <paulmck@...nel.org>
> > 
> > This commit adds vmalloc() support to mem_dump_obj().  Note that the
> > vmalloc_dump_obj() function combines the checking and dumping, in
> > contrast with the split between kmem_valid_obj() and kmem_dump_obj().
> > The reason for the difference is that the checking in the vmalloc()
> > case involves acquiring a global lock, and redundant acquisitions of
> > global locks should be avoided, even on not-so-fast paths.
> > 
> > Note that this change causes on-stack variables to be reported as
> > vmalloc() storage from kernel_clone() or similar, depending on the degree
> > of inlining that your compiler does.  This is likely more helpful than
> > the earlier "non-paged (local) memory".
> > 
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> > Cc: <linux-mm@...ck.org>
> > Reported-by: Andrii Nakryiko <andrii@...nel.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> 
> ...
> 
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -3431,6 +3431,18 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> >  }
> >  #endif	/* CONFIG_SMP */
> >  
> > +bool vmalloc_dump_obj(void *object)
> > +{
> > +	struct vm_struct *vm;
> > +	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
> > +
> > +	vm = find_vm_area(objp);
> > +	if (!vm)
> > +		return false;
> > +	pr_cont(" vmalloc allocated at %pS\n", vm->caller);
> 
> Would it be useful to print the vm area boundaries too?
> 
Do you mean va_start/va_end information?

--
Vlad Rezki