1b2441318SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 267afa38eSTim Chen /* 367afa38eSTim Chen * Manage cache of swap slots to be used for and returned from 467afa38eSTim Chen * swap. 567afa38eSTim Chen * 667afa38eSTim Chen * Copyright(c) 2016 Intel Corporation. 767afa38eSTim Chen * 867afa38eSTim Chen * Author: Tim Chen <tim.c.chen@linux.intel.com> 967afa38eSTim Chen * 1067afa38eSTim Chen * We allocate the swap slots from the global pool and put 1167afa38eSTim Chen * it into local per cpu caches. This has the advantage 1267afa38eSTim Chen * of no needing to acquire the swap_info lock every time 1367afa38eSTim Chen * we need a new slot. 1467afa38eSTim Chen * 1567afa38eSTim Chen * There is also opportunity to simply return the slot 1667afa38eSTim Chen * to local caches without needing to acquire swap_info 1767afa38eSTim Chen * lock. We do not reuse the returned slots directly but 1867afa38eSTim Chen * move them back to the global pool in a batch. This 19f0953a1bSIngo Molnar * allows the slots to coalesce and reduce fragmentation. 2067afa38eSTim Chen * 2167afa38eSTim Chen * The swap entry allocated is marked with SWAP_HAS_CACHE 2267afa38eSTim Chen * flag in map_count that prevents it from being allocated 2367afa38eSTim Chen * again from the global pool. 2467afa38eSTim Chen * 2567afa38eSTim Chen * The swap slots cache is protected by a mutex instead of 2667afa38eSTim Chen * a spin lock as when we search for slots with scan_swap_map, 2767afa38eSTim Chen * we can possibly sleep. 2867afa38eSTim Chen */ 2967afa38eSTim Chen 3067afa38eSTim Chen #include <linux/swap_slots.h> 3167afa38eSTim Chen #include <linux/cpu.h> 3267afa38eSTim Chen #include <linux/cpumask.h> 338581fd40SJakub Kicinski #include <linux/slab.h> 3467afa38eSTim Chen #include <linux/vmalloc.h> 3567afa38eSTim Chen #include <linux/mutex.h> 3654f180d3SHuang Ying #include <linux/mm.h> 3767afa38eSTim Chen 3867afa38eSTim Chen static DEFINE_PER_CPU(struct swap_slots_cache, swp_slots); 3967afa38eSTim Chen static bool swap_slot_cache_active; 40ba81f838SHuang Ying bool swap_slot_cache_enabled; 4167afa38eSTim Chen static bool swap_slot_cache_initialized; 4231f21da1SColin Ian King static DEFINE_MUTEX(swap_slots_cache_mutex); 4367afa38eSTim Chen /* Serialize swap slots cache enable/disable operations */ 4431f21da1SColin Ian King static DEFINE_MUTEX(swap_slots_cache_enable_mutex); 4567afa38eSTim Chen 4667afa38eSTim Chen static void __drain_swap_slots_cache(unsigned int type); 4767afa38eSTim Chen 48e0f3ebbaSZhen Lei #define use_swap_slot_cache (swap_slot_cache_active && swap_slot_cache_enabled) 4967afa38eSTim Chen #define SLOTS_CACHE 0x1 5067afa38eSTim Chen #define SLOTS_CACHE_RET 0x2 5167afa38eSTim Chen 5267afa38eSTim Chen static void deactivate_swap_slots_cache(void) 5367afa38eSTim Chen { 5467afa38eSTim Chen mutex_lock(&swap_slots_cache_mutex); 5567afa38eSTim Chen swap_slot_cache_active = false; 5667afa38eSTim Chen __drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET); 5767afa38eSTim Chen mutex_unlock(&swap_slots_cache_mutex); 5867afa38eSTim Chen } 5967afa38eSTim Chen 6067afa38eSTim Chen static void reactivate_swap_slots_cache(void) 6167afa38eSTim Chen { 6267afa38eSTim Chen mutex_lock(&swap_slots_cache_mutex); 6367afa38eSTim Chen swap_slot_cache_active = true; 6467afa38eSTim Chen mutex_unlock(&swap_slots_cache_mutex); 6567afa38eSTim Chen } 6667afa38eSTim Chen 6767afa38eSTim Chen /* Must not be called with cpu hot plug lock */ 6867afa38eSTim Chen void disable_swap_slots_cache_lock(void) 6967afa38eSTim Chen { 7067afa38eSTim Chen mutex_lock(&swap_slots_cache_enable_mutex); 7167afa38eSTim Chen swap_slot_cache_enabled = false; 7267afa38eSTim Chen if (swap_slot_cache_initialized) { 7367afa38eSTim Chen /* serialize with cpu hotplug operations */ 747625eccdSSebastian Andrzej Siewior cpus_read_lock(); 7567afa38eSTim Chen __drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET); 767625eccdSSebastian Andrzej Siewior cpus_read_unlock(); 7767afa38eSTim Chen } 7867afa38eSTim Chen } 7967afa38eSTim Chen 8067afa38eSTim Chen static void __reenable_swap_slots_cache(void) 8167afa38eSTim Chen { 8267afa38eSTim Chen swap_slot_cache_enabled = has_usable_swap(); 8367afa38eSTim Chen } 8467afa38eSTim Chen 8567afa38eSTim Chen void reenable_swap_slots_cache_unlock(void) 8667afa38eSTim Chen { 8767afa38eSTim Chen __reenable_swap_slots_cache(); 8867afa38eSTim Chen mutex_unlock(&swap_slots_cache_enable_mutex); 8967afa38eSTim Chen } 9067afa38eSTim Chen 9167afa38eSTim Chen static bool check_cache_active(void) 9267afa38eSTim Chen { 9367afa38eSTim Chen long pages; 9467afa38eSTim Chen 95e0f3ebbaSZhen Lei if (!swap_slot_cache_enabled) 9667afa38eSTim Chen return false; 9767afa38eSTim Chen 9867afa38eSTim Chen pages = get_nr_swap_pages(); 9967afa38eSTim Chen if (!swap_slot_cache_active) { 10067afa38eSTim Chen if (pages > num_online_cpus() * 10167afa38eSTim Chen THRESHOLD_ACTIVATE_SWAP_SLOTS_CACHE) 10267afa38eSTim Chen reactivate_swap_slots_cache(); 10367afa38eSTim Chen goto out; 10467afa38eSTim Chen } 10567afa38eSTim Chen 10667afa38eSTim Chen /* if global pool of slot caches too low, deactivate cache */ 10767afa38eSTim Chen if (pages < num_online_cpus() * THRESHOLD_DEACTIVATE_SWAP_SLOTS_CACHE) 10867afa38eSTim Chen deactivate_swap_slots_cache(); 10967afa38eSTim Chen out: 11067afa38eSTim Chen return swap_slot_cache_active; 11167afa38eSTim Chen } 11267afa38eSTim Chen 11367afa38eSTim Chen static int alloc_swap_slot_cache(unsigned int cpu) 11467afa38eSTim Chen { 11567afa38eSTim Chen struct swap_slots_cache *cache; 11667afa38eSTim Chen swp_entry_t *slots, *slots_ret; 11767afa38eSTim Chen 11867afa38eSTim Chen /* 11967afa38eSTim Chen * Do allocation outside swap_slots_cache_mutex 120e2e3fdc7SMatthew Wilcox (Oracle) * as kvzalloc could trigger reclaim and folio_alloc_swap, 12167afa38eSTim Chen * which can lock swap_slots_cache_mutex. 12267afa38eSTim Chen */ 123778e1cddSKees Cook slots = kvcalloc(SWAP_SLOTS_CACHE_SIZE, sizeof(swp_entry_t), 12454f180d3SHuang Ying GFP_KERNEL); 12567afa38eSTim Chen if (!slots) 12667afa38eSTim Chen return -ENOMEM; 12767afa38eSTim Chen 128778e1cddSKees Cook slots_ret = kvcalloc(SWAP_SLOTS_CACHE_SIZE, sizeof(swp_entry_t), 12954f180d3SHuang Ying GFP_KERNEL); 13067afa38eSTim Chen if (!slots_ret) { 13154f180d3SHuang Ying kvfree(slots); 13267afa38eSTim Chen return -ENOMEM; 13367afa38eSTim Chen } 13467afa38eSTim Chen 13567afa38eSTim Chen mutex_lock(&swap_slots_cache_mutex); 13667afa38eSTim Chen cache = &per_cpu(swp_slots, cpu); 137f90eae2aSZhen Lei if (cache->slots || cache->slots_ret) { 13867afa38eSTim Chen /* cache already allocated */ 139f90eae2aSZhen Lei mutex_unlock(&swap_slots_cache_mutex); 140f90eae2aSZhen Lei 141f90eae2aSZhen Lei kvfree(slots); 142f90eae2aSZhen Lei kvfree(slots_ret); 143f90eae2aSZhen Lei 144f90eae2aSZhen Lei return 0; 145f90eae2aSZhen Lei } 146f90eae2aSZhen Lei 14767afa38eSTim Chen if (!cache->lock_initialized) { 14867afa38eSTim Chen mutex_init(&cache->alloc_lock); 14967afa38eSTim Chen spin_lock_init(&cache->free_lock); 15067afa38eSTim Chen cache->lock_initialized = true; 15167afa38eSTim Chen } 15267afa38eSTim Chen cache->nr = 0; 15367afa38eSTim Chen cache->cur = 0; 15467afa38eSTim Chen cache->n_ret = 0; 155a2e16731STim Chen /* 156a2e16731STim Chen * We initialized alloc_lock and free_lock earlier. We use 157a2e16731STim Chen * !cache->slots or !cache->slots_ret to know if it is safe to acquire 158a2e16731STim Chen * the corresponding lock and use the cache. Memory barrier below 159a2e16731STim Chen * ensures the assumption. 160a2e16731STim Chen */ 161a2e16731STim Chen mb(); 16267afa38eSTim Chen cache->slots = slots; 16367afa38eSTim Chen cache->slots_ret = slots_ret; 16467afa38eSTim Chen mutex_unlock(&swap_slots_cache_mutex); 16567afa38eSTim Chen return 0; 16667afa38eSTim Chen } 16767afa38eSTim Chen 16867afa38eSTim Chen static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type, 16967afa38eSTim Chen bool free_slots) 17067afa38eSTim Chen { 17167afa38eSTim Chen struct swap_slots_cache *cache; 17267afa38eSTim Chen swp_entry_t *slots = NULL; 17367afa38eSTim Chen 17467afa38eSTim Chen cache = &per_cpu(swp_slots, cpu); 17567afa38eSTim Chen if ((type & SLOTS_CACHE) && cache->slots) { 17667afa38eSTim Chen mutex_lock(&cache->alloc_lock); 17767afa38eSTim Chen swapcache_free_entries(cache->slots + cache->cur, cache->nr); 17867afa38eSTim Chen cache->cur = 0; 17967afa38eSTim Chen cache->nr = 0; 18067afa38eSTim Chen if (free_slots && cache->slots) { 18154f180d3SHuang Ying kvfree(cache->slots); 18267afa38eSTim Chen cache->slots = NULL; 18367afa38eSTim Chen } 18467afa38eSTim Chen mutex_unlock(&cache->alloc_lock); 18567afa38eSTim Chen } 18667afa38eSTim Chen if ((type & SLOTS_CACHE_RET) && cache->slots_ret) { 18767afa38eSTim Chen spin_lock_irq(&cache->free_lock); 18867afa38eSTim Chen swapcache_free_entries(cache->slots_ret, cache->n_ret); 18967afa38eSTim Chen cache->n_ret = 0; 19067afa38eSTim Chen if (free_slots && cache->slots_ret) { 19167afa38eSTim Chen slots = cache->slots_ret; 19267afa38eSTim Chen cache->slots_ret = NULL; 19367afa38eSTim Chen } 19467afa38eSTim Chen spin_unlock_irq(&cache->free_lock); 19554f180d3SHuang Ying kvfree(slots); 19667afa38eSTim Chen } 19767afa38eSTim Chen } 19867afa38eSTim Chen 19967afa38eSTim Chen static void __drain_swap_slots_cache(unsigned int type) 20067afa38eSTim Chen { 20167afa38eSTim Chen unsigned int cpu; 20267afa38eSTim Chen 20367afa38eSTim Chen /* 20467afa38eSTim Chen * This function is called during 20567afa38eSTim Chen * 1) swapoff, when we have to make sure no 20667afa38eSTim Chen * left over slots are in cache when we remove 20767afa38eSTim Chen * a swap device; 20867afa38eSTim Chen * 2) disabling of swap slot cache, when we run low 20967afa38eSTim Chen * on swap slots when allocating memory and need 21067afa38eSTim Chen * to return swap slots to global pool. 21167afa38eSTim Chen * 21267afa38eSTim Chen * We cannot acquire cpu hot plug lock here as 21367afa38eSTim Chen * this function can be invoked in the cpu 21467afa38eSTim Chen * hot plug path: 21567afa38eSTim Chen * cpu_up -> lock cpu_hotplug -> cpu hotplug state callback 216e2e3fdc7SMatthew Wilcox (Oracle) * -> memory allocation -> direct reclaim -> folio_alloc_swap 21767afa38eSTim Chen * -> drain_swap_slots_cache 21867afa38eSTim Chen * 21967afa38eSTim Chen * Hence the loop over current online cpu below could miss cpu that 22067afa38eSTim Chen * is being brought online but not yet marked as online. 22167afa38eSTim Chen * That is okay as we do not schedule and run anything on a 22267afa38eSTim Chen * cpu before it has been marked online. Hence, we will not 22367afa38eSTim Chen * fill any swap slots in slots cache of such cpu. 22467afa38eSTim Chen * There are no slots on such cpu that need to be drained. 22567afa38eSTim Chen */ 22667afa38eSTim Chen for_each_online_cpu(cpu) 22767afa38eSTim Chen drain_slots_cache_cpu(cpu, type, false); 22867afa38eSTim Chen } 22967afa38eSTim Chen 23067afa38eSTim Chen static int free_slot_cache(unsigned int cpu) 23167afa38eSTim Chen { 23267afa38eSTim Chen mutex_lock(&swap_slots_cache_mutex); 23367afa38eSTim Chen drain_slots_cache_cpu(cpu, SLOTS_CACHE | SLOTS_CACHE_RET, true); 23467afa38eSTim Chen mutex_unlock(&swap_slots_cache_mutex); 23567afa38eSTim Chen return 0; 23667afa38eSTim Chen } 23767afa38eSTim Chen 238f3bc52cbSMiaohe Lin void enable_swap_slots_cache(void) 23967afa38eSTim Chen { 24067afa38eSTim Chen mutex_lock(&swap_slots_cache_enable_mutex); 241d69a9575SZhen Lei if (!swap_slot_cache_initialized) { 242d69a9575SZhen Lei int ret; 24367afa38eSTim Chen 24467afa38eSTim Chen ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "swap_slots_cache", 24567afa38eSTim Chen alloc_swap_slot_cache, free_slot_cache); 2469b7a8143STim Chen if (WARN_ONCE(ret < 0, "Cache allocation failed (%s), operating " 2479b7a8143STim Chen "without swap slots cache.\n", __func__)) 24867afa38eSTim Chen goto out_unlock; 2499b7a8143STim Chen 25067afa38eSTim Chen swap_slot_cache_initialized = true; 251d69a9575SZhen Lei } 252d69a9575SZhen Lei 25367afa38eSTim Chen __reenable_swap_slots_cache(); 25467afa38eSTim Chen out_unlock: 25567afa38eSTim Chen mutex_unlock(&swap_slots_cache_enable_mutex); 25667afa38eSTim Chen } 25767afa38eSTim Chen 25867afa38eSTim Chen /* called with swap slot cache's alloc lock held */ 25967afa38eSTim Chen static int refill_swap_slots_cache(struct swap_slots_cache *cache) 26067afa38eSTim Chen { 261f19c2568SMiaohe Lin if (!use_swap_slot_cache) 26267afa38eSTim Chen return 0; 26367afa38eSTim Chen 26467afa38eSTim Chen cache->cur = 0; 26567afa38eSTim Chen if (swap_slot_cache_active) 2665d5e8f19SHuang Ying cache->nr = get_swap_pages(SWAP_SLOTS_CACHE_SIZE, 2675d5e8f19SHuang Ying cache->slots, 1); 26867afa38eSTim Chen 26967afa38eSTim Chen return cache->nr; 27067afa38eSTim Chen } 27167afa38eSTim Chen 272bc4a68adSMiaohe Lin void free_swap_slot(swp_entry_t entry) 27367afa38eSTim Chen { 27467afa38eSTim Chen struct swap_slots_cache *cache; 27567afa38eSTim Chen 276*0827a1fbSChengming Zhou /* Large folio swap slot is not covered. */ 277*0827a1fbSChengming Zhou zswap_invalidate(entry); 278*0827a1fbSChengming Zhou 279f07e0f84SSebastian Andrzej Siewior cache = raw_cpu_ptr(&swp_slots); 280a2e16731STim Chen if (likely(use_swap_slot_cache && cache->slots_ret)) { 28167afa38eSTim Chen spin_lock_irq(&cache->free_lock); 28267afa38eSTim Chen /* Swap slots cache may be deactivated before acquiring lock */ 283f07e0f84SSebastian Andrzej Siewior if (!use_swap_slot_cache || !cache->slots_ret) { 28467afa38eSTim Chen spin_unlock_irq(&cache->free_lock); 28567afa38eSTim Chen goto direct_free; 28667afa38eSTim Chen } 28767afa38eSTim Chen if (cache->n_ret >= SWAP_SLOTS_CACHE_SIZE) { 28867afa38eSTim Chen /* 28967afa38eSTim Chen * Return slots to global pool. 29067afa38eSTim Chen * The current swap_map value is SWAP_HAS_CACHE. 29167afa38eSTim Chen * Set it to 0 to indicate it is available for 29267afa38eSTim Chen * allocation in global pool 29367afa38eSTim Chen */ 29467afa38eSTim Chen swapcache_free_entries(cache->slots_ret, cache->n_ret); 29567afa38eSTim Chen cache->n_ret = 0; 29667afa38eSTim Chen } 29767afa38eSTim Chen cache->slots_ret[cache->n_ret++] = entry; 29867afa38eSTim Chen spin_unlock_irq(&cache->free_lock); 29967afa38eSTim Chen } else { 30067afa38eSTim Chen direct_free: 30167afa38eSTim Chen swapcache_free_entries(&entry, 1); 30267afa38eSTim Chen } 30367afa38eSTim Chen } 30467afa38eSTim Chen 305e2e3fdc7SMatthew Wilcox (Oracle) swp_entry_t folio_alloc_swap(struct folio *folio) 30667afa38eSTim Chen { 3072406b76fSWei Yang swp_entry_t entry; 30867afa38eSTim Chen struct swap_slots_cache *cache; 30967afa38eSTim Chen 31038d8b4e6SHuang Ying entry.val = 0; 31138d8b4e6SHuang Ying 312e2e3fdc7SMatthew Wilcox (Oracle) if (folio_test_large(folio)) { 313d0637c50SBarry Song if (IS_ENABLED(CONFIG_THP_SWAP) && arch_thp_swp_supported()) 314e2e3fdc7SMatthew Wilcox (Oracle) get_swap_pages(1, &entry, folio_nr_pages(folio)); 315bb98f2c5STejun Heo goto out; 31638d8b4e6SHuang Ying } 31738d8b4e6SHuang Ying 31867afa38eSTim Chen /* 31967afa38eSTim Chen * Preemption is allowed here, because we may sleep 32067afa38eSTim Chen * in refill_swap_slots_cache(). But it is safe, because 32167afa38eSTim Chen * accesses to the per-CPU data structure are protected by the 32267afa38eSTim Chen * mutex cache->alloc_lock. 32367afa38eSTim Chen * 32467afa38eSTim Chen * The alloc path here does not touch cache->slots_ret 32567afa38eSTim Chen * so cache->free_lock is not taken. 32667afa38eSTim Chen */ 32767afa38eSTim Chen cache = raw_cpu_ptr(&swp_slots); 32867afa38eSTim Chen 329a2e16731STim Chen if (likely(check_cache_active() && cache->slots)) { 33067afa38eSTim Chen mutex_lock(&cache->alloc_lock); 33167afa38eSTim Chen if (cache->slots) { 33267afa38eSTim Chen repeat: 33367afa38eSTim Chen if (cache->nr) { 3342406b76fSWei Yang entry = cache->slots[cache->cur]; 3352406b76fSWei Yang cache->slots[cache->cur++].val = 0; 33667afa38eSTim Chen cache->nr--; 3372406b76fSWei Yang } else if (refill_swap_slots_cache(cache)) { 33867afa38eSTim Chen goto repeat; 33967afa38eSTim Chen } 34067afa38eSTim Chen } 34167afa38eSTim Chen mutex_unlock(&cache->alloc_lock); 34267afa38eSTim Chen if (entry.val) 343bb98f2c5STejun Heo goto out; 34467afa38eSTim Chen } 34567afa38eSTim Chen 3465d5e8f19SHuang Ying get_swap_pages(1, &entry, 1); 347bb98f2c5STejun Heo out: 348e2e3fdc7SMatthew Wilcox (Oracle) if (mem_cgroup_try_charge_swap(folio, entry)) { 3494081f744SMatthew Wilcox (Oracle) put_swap_folio(folio, entry); 350bb98f2c5STejun Heo entry.val = 0; 351bb98f2c5STejun Heo } 35267afa38eSTim Chen return entry; 35367afa38eSTim Chen } 354