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Date:   Mon, 15 Mar 2021 11:06:59 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Luis Henriques <lhenriques@suse.de>
Cc:     Miklos Szeredi <miklos@szeredi.hu>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: fuse: kernel BUG at mm/truncate.c:763!
Message-ID: <20210315110659.GT2577561@casper.infradead.org>
References: <YEsryBEFq4HuLKBs@suse.de>
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 <YEtc54pWLLjb6SgL@suse.de>
 <20210312131123.GZ3479805@casper.infradead.org>
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On Mon, Mar 15, 2021 at 09:47:45AM +0000, Luis Henriques wrote:
> On Fri, Mar 12, 2021 at 01:11:23PM +0000, Matthew Wilcox wrote:
> > On Fri, Mar 12, 2021 at 12:21:59PM +0000, Luis Henriques wrote:
> > > > > I've seen a bug report (5.10.16 kernel splat below) that seems to be
> > > > > reproducible in kernels as early as 5.4.
> > 
> > If this is reproducible, can you turn this BUG_ON into a VM_BUG_ON_PAGE()
> > so we know what kind of problem we're dealing with?  Assuming the SUSE
> > tumbleweed kernels enable CONFIG_DEBUG_VM, which I'm sure they do.
> 
> Just to make sure I got this right, you want to test something like this:
> 
>  				}
>  			}
> -			BUG_ON(page_mapped(page));
> +			VM_BUG_ON_PAGE(page_mapped(page), page);
>  			ret2 = do_launder_page(mapping, page);
>  			if (ret2 == 0) {
>  				if (!invalidate_complete_page2(mapping, page))

Yes, exactly.