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Date:   Wed, 18 Jan 2023 17:42:47 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, linux-afs@lists.infradead.org,
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Subject: Re: [PATCH 8/9] btrfs: handle a NULL folio in
 extent_range_redirty_for_io
Message-ID: <20230118164247.GC7584@lst.de>
References: <20230118094329.9553-1-hch@lst.de> <20230118094329.9553-9-hch@lst.de> <Y8gZmTFB6vCivxsY@casper.infradead.org>
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On Wed, Jan 18, 2023 at 04:08:57PM +0000, Matthew Wilcox wrote:
> On Wed, Jan 18, 2023 at 10:43:28AM +0100, Christoph Hellwig wrote:
> > filemap_get_folio can return NULL, skip those cases.
> 
> Hmm, I'm not sure that's true.  We have one place that calls
> extent_range_redirty_for_io(), and it previously calls
> extent_range_clear_dirty_for_io() which has an explicit
> 
>                 BUG_ON(!page); /* Pages should be in the extent_io_tree */
> 
> so I'm going to say this one can't happen either.  I haven't delved far
> enough into btrfs to figure out why it can't happen.

I'll drop this patch for now.