On Sat, Jun 8, 2024 at 7:17 AM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > > [..] > > > One problem is that even if zswap was never enabled, the warning will > > > be emitted just if CONFIG_ZSWAP is on. Perhaps we need a variable or > > > static key if zswap was "ever" enabled. > > > > > > Barry, I suspect your is_zswap_enabled() check is deficient for > > > similar reasons, zswap could have been enabled before then became > > > disabled. > > > > I don't understand this. if zswap was enabled before but is disabled when > > I am loading data, will I get corrupted data before zswap was once enabled? > > If not, it seems nothing important. > > If zswap was enabled and then disabled, some pages may still be in > zswap. We do not load the pages from zswap when it is disabled, we > just stop storing new pages. > > So if you just rely in checking whether zswap is enabled at swapin > time to decide whether to use large folios, you may end up with a > situation where zswap is disabled, yet parts of the large folio you > are trying to swapin (or all of it) is in zswap. > > This is why I think we'll need to track whether zswap was ever enabled > instead (or if a page was ever stored). Thanks! It doesn't seem good. Do we have a simple way to clean zswap when it is disabled? seems not easy? Just like we do swapoff, or disable cache, we ensure they are clean - this is a real "disable". Thanks Barry
