Re: [PATCH v5 3/3] mm/khugepaged: maintain page cache uptodate flag

[Song Liu]

On Thu, Mar 23, 2023 at 2:56 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Thu, Mar 23, 2023 at 12:07:46PM -0700, Hugh Dickins wrote:
> > On an earlier audit, for different reasons, I did also run across
> > lib/buildid.c build_id_parse() using find_get_page() without checking
> > PageUptodate() - looks as if it might do the wrong thing if it races
> > with khugepaged collapsing text to huge, and should probably have a
> > similar fix.
>
> That shouldn't be using find_get_page().  It should probably use
> read_cache_folio() which will actually read in the data if it's not
> present in the page cache, and return an ERR_PTR if the data couldn't
> be read.

build_id_parse() can be called from NMI, so I don't think we can let
read_cache_folio() read-in the data.

Thanks,
Song