linux-kernel - Re: [PATCH 10/10] mm/hugetlb: share the i_mmap

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Date:	Wed, 5 Nov 2014 08:04:09 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Davidlohr Bueso <dave@...olabs.net>
cc:	Hugh Dickins <hughd@...gle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>, riel@...hat.com,
	mgorman@...e.de, peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 10/10] mm/hugetlb: share the i_mmap_rwsem

On Tue, 4 Nov 2014, Davidlohr Bueso wrote:
> 8<------------------------------------------------
> From: Davidlohr Bueso <dave@...olabs.net>
> Subject: [PATCH 11/10] mm/memory.c: share the i_mmap_rwsem
> 
> The unmap_mapping_range family of functions do the unmapping
> of user pages (ultimately via zap_page_range_single) without
> touching the actual interval tree, thus share the lock.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

Acked-by: Hugh Dickins <hughd@...gle.com>

Yes, thanks, let's get this 11/10 into mmotm along with the rest,
but put the hugetlb 10/10 on the shelf for now, until we've had
time to contemplate it more deeply.

> ---
>  mm/memory.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 2ca3105..06f2458 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2396,12 +2396,12 @@ void unmap_mapping_range(struct address_space *mapping,
>  		details.last_index = ULONG_MAX;
>  
>  
> -	i_mmap_lock_write(mapping);
> +	i_mmap_lock_read(mapping);
>  	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
>  		unmap_mapping_range_tree(&mapping->i_mmap, &details);
>  	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
>  		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
> -	i_mmap_unlock_write(mapping);
> +	i_mmap_unlock_read(mapping);
>  }
>  EXPORT_SYMBOL(unmap_mapping_range);
>  
> -- 
> 1.8.4.5
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