linux-kernel - Re: [PATCH V2 4/8] mm/highmem: Add VM_BUG_ON() to mem*

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Date:   Wed, 10 Feb 2021 08:29:01 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Sterba <dsterba@...e.cz>,
        Matthew Wilcox <willy@...radead.org>, clm@...com,
        josef@...icpanda.com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V2 4/8] mm/highmem: Add VM_BUG_ON() to mem*_page() calls

On Wed, Feb 10, 2021 at 12:55:02PM +0000, Christoph Hellwig wrote:
> On Tue, Feb 09, 2021 at 10:22:17PM -0800, ira.weiny@...el.com wrote:
> > From: Ira Weiny <ira.weiny@...el.com>
> > 
> > Add VM_BUG_ON bounds checks to ensure the newly lifted and created page
> > memory operations do not result in corrupted data in neighbor pages and
> > to make them consistent with zero_user().[1][2]
> 
> s/VM_BUG_ON/BUG_ON/g ?

Andrew wanted VM_BUG_ON.[1]

And I thought it was a good idea.  Any file system development should have
tests with DEBUG_VM which should cover Matthew's concern while not having the
overhead in production.  Seemed like a decent compromise?

Ira

[1] https://lore.kernel.org/lkml/20210209131103.b46e80db675fec8bec8d2ad1@linux-foundation.org/

> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@....de>