linux-kernel - Re: [PATCH 2/3] mm/sparse: Optimize sparse_add_one

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Message-Id: <20190320112730.GE13626@rapoport-lnx>
Date:   Wed, 20 Mar 2019 13:27:30 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        pasha.tatashin@...cle.com, mhocko@...e.com,
        rppt@...ux.vnet.ibm.com, richard.weiyang@...il.com,
        linux-mm@...ck.org
Subject: Re: [PATCH 2/3] mm/sparse: Optimize sparse_add_one_section()

On Wed, Mar 20, 2019 at 06:13:18PM +0800, Baoquan He wrote:
> Hi Mike,
> 
> On 03/20/19 at 09:56am, Mike Rapoport wrote:
>  > @@ -697,16 +697,17 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
> > >  	ret = sparse_index_init(section_nr, nid);
> > >  	if (ret < 0 && ret != -EEXIST)
> > >  		return ret;
> > > -	ret = 0;
> > > -	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
> > > -	if (!memmap)
> > > -		return -ENOMEM;
> > > +
> > >  	usemap = __kmalloc_section_usemap();
> > > -	if (!usemap) {
> > > -		__kfree_section_memmap(memmap, altmap);
> > > +	if (!usemap)
> > > +		return -ENOMEM;
> > > +	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
> > > +	if (!memmap) {
> > > +		kfree(usemap);
> > 
> > If you are anyway changing this why not to switch to goto's for error
> > handling?
> 
> I update code change as below, could you check if it's OK to you?
> 
> Thanks
> Baoquan
> 
> From 39b679b6f34f6acbc05351be8569d23bae3c0458 Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@...hat.com>
> Date: Fri, 15 Mar 2019 16:03:52 +0800
> Subject: [PATCH] mm/sparse: Optimize sparse_add_one_section()
> 
> Reorder the allocation of usemap and memmap since usemap allocation
> is much smaller and simpler. Otherwise hard work is done to make
> memmap ready, then have to rollback just because of usemap allocation
> failure.
> 
> Meanwhile update the error handler to cover usemap allocation failure
> too.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  mm/sparse.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index a99e0b253927..0e842b924be6 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -699,20 +699,21 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
>  	ret = sparse_index_init(section_nr, nid);
>  	if (ret < 0 && ret != -EEXIST)
>  		return ret;
> -	ret = 0;
> -	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
> -	if (!memmap)
> -		return -ENOMEM;
> +
>  	usemap = __kmalloc_section_usemap();
> -	if (!usemap) {
> -		__kfree_section_memmap(memmap, altmap);
> +	if (!usemap)
>  		return -ENOMEM;
> +	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
> +	if (!memmap) {
> +		ret = -ENOMEM;
> +		goto out2;

I'd name the label out_free_usemap.

>  	}
>  
> +	ret = 0;
>  	ms = __pfn_to_section(start_pfn);
>  	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
>  		ret = -EEXIST;
> -		goto out;
> +		goto out2;
>  	}

I've missed this previously, but it seems that this check can be moved
before the allocations, which simplifies the code a bit more.

>  
>  	/*
> @@ -724,11 +725,11 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
>  	section_mark_present(ms);
>  	sparse_init_one_section(ms, section_nr, memmap, usemap);
>  
> +	return ret;
>  out:
> -	if (ret < 0) {
> -		kfree(usemap);
> -		__kfree_section_memmap(memmap, altmap);
> -	}
> +	__kfree_section_memmap(memmap, altmap);
> +out2:
> +	kfree(usemap);
>  	return ret;
>  }
>  
> -- 
> 2.17.2
> 

-- 
Sincerely yours,
Mike.