linux-kernel - Re: [PATCH] mm, hugetlb: move the error handle logic out of normal code path

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Message-ID: <20140516075730.GA22818@dhcp22.suse.cz>
Date:	Fri, 16 May 2014 09:57:30 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jianyu Zhan <nasa4836@...il.com>, iamjoonsoo.kim@....com,
	aneesh.kumar@...ux.vnet.ibm.com, n-horiguchi@...jp.nec.com,
	aarcange@...hat.com, steve.capper@...aro.org, davidlohr@...com,
	kirill.shutemov@...ux.intel.com, dave.hansen@...ux.intel.com,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, hugetlb: move the error handle logic out of normal
 code path

On Thu 15-05-14 15:36:20, Andrew Morton wrote:
> On Thu, 15 May 2014 11:01:42 +0200 Michal Hocko <mhocko@...e.cz> wrote:
> 
> > On Wed 14-05-14 15:10:59, Jianyu Zhan wrote:
> > > alloc_huge_page() now mixes normal code path with error handle logic.
> > > This patches move out the error handle logic, to make normal code
> > > path more clean and redue code duplicate.
> > 
> > I don't know. Part of the function returns and cleans up on its own and
> > other part relies on clean up labels. This is not so much nicer than the
> > previous state.
> 
> That's actually a common pattern:
> 
> foo()
> {
> 	if (check which doesn't change any state)
> 		return -Efoo;
> 	if (another check which doesn't change any state)
> 		return -Ebar;
> 
> 	do_something_which_changes_state()
> 	
> 	if (another check)
> 		goto undo_that_state_chage;
> 	...
> 
> undo_that_state_change:
> 	...
> }

Right. I have misread the previous vma_needs_reservation and
hugepage_subpool_get_pages error path and already considered it as a
changing state one. Sorry about the confusion.
-- 
Michal Hocko
SUSE Labs
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