linux-kernel - Re: [PATCH 1/5] mm: compaction: Remove redundant VM_BUG_ON() in compact

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Date:   Tue, 10 Jan 2023 23:37:25 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] mm: compaction: Remove redundant VM_BUG_ON() in
 compact_zone()

On Tue, Jan 10, 2023 at 03:25:32PM -0800, Andrew Morton wrote:
> On Tue, 10 Jan 2023 13:37:57 +0000 Matthew Wilcox <willy@...radead.org> wrote:
> 
> > On Tue, Jan 10, 2023 at 09:36:18PM +0800, Baolin Wang wrote:
> > > The compaction_suitable() will never return values other than COMPACT_SUCCESS,
> > > COMPACT_SKIPPED and COMPACT_CONTINUE, so after validation of COMPACT_SUCCESS
> > > and COMPACT_SKIPPED, we will never hit other unexpected case. Thus remove
> > > the redundant VM_BUG_ON() validation for the return values of compaction_suitable().
> > 
> > I don't understand why we'd remove this check.
> 
> Well, just from code inspection it serves no purpose.
> 
> Such an assertion might be useful during early code development, but I
> think we can consider compaction_suitable() to adequately debugged by
> now?

What if compaction_suitable() is modified to return another value?
This seems like a relatively innocuous check.