From: Yosry Ahmed <yosryahmed@google.com> mainline inclusion from mainline-v6.11-rc1 commit 2d4d2b1cfb85cc07f6d5619acb882d8b11e55cf4 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IC3A3N Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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@google.com: expose zswap_never_enabled() in the header] Link: https://lkml.kernel.org/r/Zmjf0Dr8s9xSW41X@google.com Link: https://lkml.kernel.org/r/20240611024516.1375191-2-yosryahmed@google.com Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Cc: Barry Song <baohua@kernel.org> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Chris Li <chrisl@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: include/linux/zswap.h mm/zswap.c [Context conflicts: patch 25cd241408a2 "mm: zswap: fix data loss on SWP_SYNCHRONOUS_IO devices" and 5b297f70bb26 "mm: zswap: inline and remove zswap_entry_find_get()" are not merged.] Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> --- include/linux/zswap.h | 6 ++++++ mm/zswap.c | 10 ++++++++++ 2 files changed, 16 insertions(+) diff --git a/include/linux/zswap.h b/include/linux/zswap.h index 2a60ce39cfde..4683a8fe0e5b 100644 --- a/include/linux/zswap.h +++ b/include/linux/zswap.h @@ -15,6 +15,7 @@ bool zswap_load(struct folio *folio); void zswap_invalidate(int type, pgoff_t offset); void zswap_swapon(int type); void zswap_swapoff(int type); +bool zswap_never_enabled(void); #else @@ -32,6 +33,11 @@ static inline void zswap_invalidate(int type, pgoff_t offset) {} static inline void zswap_swapon(int type) {} static inline void zswap_swapoff(int type) {} +static inline bool zswap_never_enabled(void) +{ + return false; +} + #endif #endif /* _LINUX_ZSWAP_H */ diff --git a/mm/zswap.c b/mm/zswap.c index c7e558167a3e..491487925192 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -84,6 +84,7 @@ 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 *); @@ -144,6 +145,11 @@ module_param_named(exclusive_loads, zswap_exclusive_loads_enabled, bool, 0644); /* Number of zpools in zswap_pool (empirically determined for scalability) */ #define ZSWAP_NR_ZPOOLS 32 +bool zswap_never_enabled(void) +{ + return !static_branch_maybe(CONFIG_ZSWAP_DEFAULT_ON, &zswap_ever_enabled); +} + /********************************* * data structures **********************************/ @@ -1410,6 +1416,9 @@ bool zswap_load(struct folio *folio) VM_WARN_ON_ONCE(!folio_test_locked(folio)); + if (zswap_never_enabled()) + return false; + /* find */ spin_lock(&tree->lock); entry = zswap_entry_find_get(&tree->rbroot, offset); @@ -1611,6 +1620,7 @@ 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; -- 2.25.1