linux-kernel - Re: [RFC][PATCH] hugetlb: fix resv

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Message-ID: <4FBA8829.3010800@jp.fujitsu.com>
Date:	Mon, 21 May 2012 14:23:37 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	dave@...ux.vnet.ibm.com
CC:	cl@...ux.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	aarcange@...hat.com, kosaki.motohiro@...fujitsu.com,
	hughd@...gle.com, rientjes@...gle.com, adobriyan@...il.com,
	akpm@...ux-foundation.org, mel@....ul.ie
Subject: Re: [RFC][PATCH] hugetlb: fix resv_map leak in error path

On 5/18/2012 2:46 PM, Dave Hansen wrote:
> When called for anonymous (non-shared) mappings,
> hugetlb_reserve_pages() does a resv_map_alloc().  It depends on
> code in hugetlbfs's vm_ops->close() to release that allocation.
> 
> However, in the mmap() failure path, we do a plain unmap_region()
> without the remove_vma() which actually calls vm_ops->close().
> 
> This is a decent fix.  This leak could get reintroduced if
> new code (say, after hugetlb_reserve_pages() in
> hugetlbfs_file_mmap()) decides to return an error.  But, I think
> it would have to unroll the reservation anyway.
> 
> This hasn't been extensively tested.  Pretty much compile and
> boot tested along with Christoph's test case.
> 
> Comments?
> 
> 
> Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>
> ---

I don't think this is cleaner fix. but I also think we should fix the leak
asap. so Let's simple fix first.

Acked-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

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