On Tue, Jun 25, 2024 at 5:01 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > The quilt patch titled > Subject: mm: zswap: add zswap_never_enabled() > has been removed from the -mm tree. Its filename was > mm-zswap-add-zswap_never_enabled.patch > > This patch was dropped because it was merged into the mm-stable branch > of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > > ------------------------------------------------------ > From: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > Subject: mm: zswap: add zswap_never_enabled() > Date: Tue, 11 Jun 2024 02:45:15 +0000 > > Add zswap_never_enabled() to skip the xarray lookup in zswap_load() if > zswap was never enabled on the system. It is implemented using static > branches for efficiency, as enabling zswap should be a rare event. This > could shave some cycles off zswap_load() when CONFIG_ZSWAP is used but > zswap is never enabled. > > However, the real motivation behind this patch is two-fold: > - Incoming large folio swapin work will need to fallback to order-0 > folios if zswap was ever enabled, because any part of the folio could be > in zswap, until proper handling of large folios with zswap is added. > > - A warning and recovery attempt will be added in a following change in > case the above was not done incorrectly. Zswap will fail the read if > the folio is large and it was ever enabled. > > Expose zswap_never_enabled() in the header for the swapin work to use > it later. > > [yosryahmed@xxxxxxxxxx: expose zswap_never_enabled() in the header] > Link: https://lkml.kernel.org/r/Zmjf0Dr8s9xSW41X@xxxxxxxxxx > Link: https://lkml.kernel.org/r/20240611024516.1375191-2-yosryahmed@xxxxxxxxxx > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx> > Cc: Barry Song <baohua@xxxxxxxxxx> > Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx> > Cc: Chris Li <chrisl@xxxxxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > include/linux/zswap.h | 6 ++++++ > mm/zswap.c | 10 ++++++++++ > 2 files changed, 16 insertions(+) > > --- a/include/linux/zswap.h~mm-zswap-add-zswap_never_enabled > +++ a/include/linux/zswap.h > @@ -36,6 +36,7 @@ void zswap_memcg_offline_cleanup(struct > void zswap_lruvec_state_init(struct lruvec *lruvec); > void zswap_folio_swapin(struct folio *folio); > bool zswap_is_enabled(void); > +bool zswap_never_enabled(void); > #else > > struct zswap_lruvec_state {}; > @@ -64,6 +65,11 @@ static inline bool zswap_is_enabled(void > { > return false; > } > + > +static inline bool zswap_never_enabled(void) > +{ > + return false; Hi Yosry & Andrew, Sorry for reporting the error too late. It should be "return true". As it has been in mm-stable, do we still have a way to fix it? > +} > > #endif > > --- a/mm/zswap.c~mm-zswap-add-zswap_never_enabled > +++ a/mm/zswap.c > @@ -83,6 +83,7 @@ static bool zswap_pool_reached_full; > static int zswap_setup(void); > > /* Enable/disable zswap */ > +static DEFINE_STATIC_KEY_MAYBE(CONFIG_ZSWAP_DEFAULT_ON, zswap_ever_enabled); > static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON); > static int zswap_enabled_param_set(const char *, > const struct kernel_param *); > @@ -136,6 +137,11 @@ bool zswap_is_enabled(void) > return zswap_enabled; > } > > +bool zswap_never_enabled(void) > +{ > + return !static_branch_maybe(CONFIG_ZSWAP_DEFAULT_ON, &zswap_ever_enabled); > +} > + > /********************************* > * data structures > **********************************/ > @@ -1557,6 +1563,9 @@ bool zswap_load(struct folio *folio) > > VM_WARN_ON_ONCE(!folio_test_locked(folio)); > > + if (zswap_never_enabled()) > + return false; > + > /* > * When reading into the swapcache, invalidate our entry. The > * swapcache can be the authoritative owner of the page and > @@ -1735,6 +1744,7 @@ static int zswap_setup(void) > zpool_get_type(pool->zpools[0])); > list_add(&pool->list, &zswap_pools); > zswap_has_pool = true; > + static_branch_enable(&zswap_ever_enabled); > } else { > pr_err("pool creation failed\n"); > zswap_enabled = false; > _ > > Patches currently in -mm which might be from yosryahmed@xxxxxxxxxx are > >
