Re: [PATCH] mm: zswap: fix missing folio cleanup in writeback race path

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On Tue, Feb 27, 2024 at 12:55 AM Greg KH <greg@xxxxxxxxx> wrote:
>
> On Mon, Feb 26, 2024 at 10:10:17PM +0000, Yosry Ahmed wrote:
> > In zswap_writeback_entry(), after we get a folio from
> > __read_swap_cache_async(), we grab the tree lock again to check that the
> > swap entry was not invalidated and recycled.  If it was, we delete the
> > folio we just added to the swap cache and exit.
> >
> > However, __read_swap_cache_async() returns the folio locked when it is
> > newly allocated, which is always true for this path, and the folio is
> > ref'd.  Make sure to unlock and put the folio before returning.
> >
> > This was discovered by code inspection, probably because this path handles
> > a race condition that should not happen often, and the bug would not crash
> > the system, it will only strand the folio indefinitely.
> >
> > Link: https://lkml.kernel.org/r/20240125085127.1327013-1-yosryahmed@xxxxxxxxxx
> > Fixes: 04fc7816089c ("mm: fix zswap writeback race condition")
> > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> > Reviewed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> > Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
> > Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > (cherry picked from commit e3b63e966cac0bf78aaa1efede1827a252815a1d)
> > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
>
> What tree is this for?

This is for 6.6.y, sorry I messed up the subject prefix. Do I need to resend?





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