linux-kernel - Re: [PATCH -V9 04/15] hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages

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Message-ID: <871uljnp71.fsf@skywalker.in.ibm.com>
Date:	Wed, 13 Jun 2012 22:07:06 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, kamezawa.hiroyu@...fujitsu.com,
	dhillf@...il.com, rientjes@...gle.com, akpm@...ux-foundation.org,
	hannes@...xchg.org, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH -V9 04/15] hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages

Michal Hocko <mhocko@...e.cz> writes:

> On Wed 13-06-12 15:57:23, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
>> 
>> Use a mmu_gather instead of a temporary linked list for accumulating
>> pages when we unmap a hugepage range
>
> Sorry for coming up with the comment that late but you owe us an
> explanation _why_ you are doing this.
>
> I assume that this fixes a real problem when we take i_mmap_mutex
> already up in 
> unmap_mapping_range
>   mutex_lock(&mapping->i_mmap_mutex);
>   unmap_mapping_range_tree | unmap_mapping_range_list 
>     unmap_mapping_range_vma
>       zap_page_range_single
>         unmap_single_vma
> 	  unmap_hugepage_range
> 	    mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
>
> And that this should have been marked for stable as well (I haven't
> checked when this has been introduced).

Switch to mmu_gather is to get rid of the use of page->lru so that i can use it for
active list.


-aneesh

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