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SubjectRe: linux-next: manual merge of the mm-stable tree with the cifs tree
Date
Matthew Wilcox <willy@infradead.org> wrote:

> > + start = folio_pos(folio); /* May regress with THPs */
>
> What does this comment mean?

"start" may end up going backwards if it's pointing to the middle of a folio.

> > + /* At this point we hold neither the i_pages lock nor the
> > + * page lock: the page may be truncated or invalidated
> > + * (changing page->mapping to NULL), or even swizzled
> > + * back from swapper_space to tmpfs file mapping
>
> Where does this comment come from? This is cifs, not tmpfs. You'll
> never be asked to writeback a page from the swap cache. Dirty pages
> can be truncated, so the first half of the comment is still accurate.
> I'd rather it moved down to below the folio lock, and was rephrased
> so it described why we're checking everything again.

I picked it up into afs from somewhere - nfs maybe? The same comment is in
fs/btrfs/extent_io.c. grep for 'swizzled' in fs/. You modified the comment
in b93b016313b3ba8003c3b8bb71f569af91f19fc7 in 2018, so it's been around a
while.

David

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