Re: [PATCH 6.1.y] mm: zswap: fix missing folio cleanup in writeback race path

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Feb 26, 2024 at 10:03:40PM +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@google.com
> Fixes: 04fc7816089c ("mm: fix zswap writeback race condition")
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
> Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Reviewed-by: Nhat Pham <nphamcs@gmail.com>
> Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> (cherry picked from commit e3b63e966cac0bf78aaa1efede1827a252815a1d)
> 
> Change-Id: I0aef4c659c6a29b45d78bf6a7e8330c7ab246f15

Why is Change-Id: in here?  checkpatch.pl should have warned you of that :(

Please fix and resend.

thanks,

greg k-h