On Thu, Feb 08, 2024 at 02:32:54AM +0000, chengming.zhou@xxxxxxxxx wrote:
> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
>
> We have to invalidate any duplicate entry even when !zswap_enabled
> since zswap can be disabled anytime. If the folio store success before,
> then got dirtied again but zswap disabled, we won't invalidate the old
> duplicate entry in the zswap_store(). So later lru writeback may
> overwrite the new data in swapfile.
>
> Fixes: 42c06a0e8ebe ("mm: kill frontswap")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Nice, this is easier to backport and should be less disruptive to
mm-unstable as well. It makes sense to me to put the optimization and
cleanup that was cut out into a separate patch on top of mm-unstable.
> mm/zswap.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index fe7ee2640c69..32633d0597dc 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1516,7 +1516,7 @@ bool zswap_store(struct folio *folio)
> if (folio_test_large(folio))
> return false;
>
> - if (!zswap_enabled || !tree)
> + if (!tree)
> return false;
>
> /*
> @@ -1531,6 +1531,10 @@ bool zswap_store(struct folio *folio)
> zswap_invalidate_entry(tree, dupentry);
> }
> spin_unlock(&tree->lock);
> +
> + if (!zswap_enabled)
> + return false;
> +
> objcg = get_obj_cgroup_from_folio(folio);
> if (objcg && !obj_cgroup_may_zswap(objcg)) {
> memcg = get_mem_cgroup_from_objcg(objcg);
