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From: Uladzislau Rezki <urezki@gmail.com>
Date: Wed, 31 Jan 2024 10:49:17 +0100
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>, linux-mm@kvack.org,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>, Baoquan He <bhe@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	Dave Chinner <david@fromorbit.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Subject: Re: [PATCH 2/2] mm: vmalloc: Refactor vmalloc_dump_obj() function
Message-ID: <ZboXnWWxTAk2WKnb@pc636>
References: <20240124180920.50725-1-urezki@gmail.com>
 <20240124180920.50725-2-urezki@gmail.com>
 <b49d2302-ace3-4306-b18f-70e8d7960111@lucifer.local>
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In-Reply-To: <b49d2302-ace3-4306-b18f-70e8d7960111@lucifer.local>

On Tue, Jan 30, 2024 at 06:50:48PM +0000, Lorenzo Stoakes wrote:
> On Wed, Jan 24, 2024 at 07:09:20PM +0100, Uladzislau Rezki (Sony) wrote:
> > This patch tends to simplify the function in question,
> > by removing an extra stack "objp" variable, returning
> > back to an early exit approach if spin_trylock() fails
> > or VA was not found.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > ---
> >  mm/vmalloc.c | 33 +++++++++++++++++----------------
> >  1 file changed, 17 insertions(+), 16 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index b8be601b056d..449f45b0e474 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -4696,34 +4696,35 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
> >  #ifdef CONFIG_PRINTK
> >  bool vmalloc_dump_obj(void *object)
> >  {
> > -	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
> >  	const void *caller;
> > +	struct vm_struct *vm;
> >  	struct vmap_area *va;
> >  	struct vmap_node *vn;
> >  	unsigned long addr;
> >  	unsigned int nr_pages;
> > -	bool success = false;
> > -
> > -	vn = addr_to_node((unsigned long)objp);
> >
> > -	if (spin_trylock(&vn->busy.lock)) {
> > -		va = __find_vmap_area((unsigned long)objp, &vn->busy.root);
> > +	addr = PAGE_ALIGN((unsigned long) object);
> > +	vn = addr_to_node(addr);
> >
> > -		if (va && va->vm) {
> > -			addr = (unsigned long)va->vm->addr;
> > -			caller = va->vm->caller;
> > -			nr_pages = va->vm->nr_pages;
> > -			success = true;
> > -		}
> > +	if (!spin_trylock(&vn->busy.lock))
> > +		return false;
> >
> > +	va = __find_vmap_area(addr, &vn->busy.root);
> > +	if (!va || !va->vm) {
> >  		spin_unlock(&vn->busy.lock);
> > +		return false;
> >  	}
> >
> > -	if (success)
> > -		pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
> > -			nr_pages, addr, caller);
> > +	vm = va->vm;
> > +	addr = (unsigned long) vm->addr;
> 
> Hmm not so nice to reuse addr here for something different, might be nice
> to have separate obj_addr and vm_addr or something. But it's not critical!
> 
> > +	caller = vm->caller;
> > +	nr_pages = vm->nr_pages;
> > +	spin_unlock(&vn->busy.lock);
> >
> > -	return success;
> > +	pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n",
> > +		nr_pages, addr, caller);
> > +
> > +	return true;
> >  }
> >  #endif
> >
> > --
> > 2.39.2
> >
> 
> Other than the nit, which I don't insist on, this is a big improvement so,
> 
> Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
>

Thanks!

--
Uladzislau Rezki