1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/swap_cgroup.h> 3 #include <linux/vmalloc.h> 4 #include <linux/mm.h> 5 6 #include <linux/swapops.h> /* depends on mm.h include */ 7 8 static DEFINE_MUTEX(swap_cgroup_mutex); 9 struct swap_cgroup_ctrl { 10 struct page **map; 11 unsigned long length; 12 spinlock_t lock; 13 }; 14 15 static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES]; 16 17 struct swap_cgroup { 18 unsigned short id; 19 }; 20 #define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup)) 21 22 /* 23 * SwapCgroup implements "lookup" and "exchange" operations. 24 * In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge 25 * against SwapCache. At swap_free(), this is accessed directly from swap. 26 * 27 * This means, 28 * - we have no race in "exchange" when we're accessed via SwapCache because 29 * SwapCache(and its swp_entry) is under lock. 30 * - When called via swap_free(), there is no user of this entry and no race. 31 * Then, we don't need lock around "exchange". 32 * 33 * TODO: we can push these buffers out to HIGHMEM. 34 */ 35 36 /* 37 * allocate buffer for swap_cgroup. 38 */ 39 static int swap_cgroup_prepare(int type) 40 { 41 struct page *page; 42 struct swap_cgroup_ctrl *ctrl; 43 unsigned long idx, max; 44 45 ctrl = &swap_cgroup_ctrl[type]; 46 47 for (idx = 0; idx < ctrl->length; idx++) { 48 page = alloc_page(GFP_KERNEL | __GFP_ZERO); 49 if (!page) 50 goto not_enough_page; 51 ctrl->map[idx] = page; 52 53 if (!(idx % SWAP_CLUSTER_MAX)) 54 cond_resched(); 55 } 56 return 0; 57 not_enough_page: 58 max = idx; 59 for (idx = 0; idx < max; idx++) 60 __free_page(ctrl->map[idx]); 61 62 return -ENOMEM; 63 } 64 65 static struct swap_cgroup *__lookup_swap_cgroup(struct swap_cgroup_ctrl *ctrl, 66 pgoff_t offset) 67 { 68 struct page *mappage; 69 struct swap_cgroup *sc; 70 71 mappage = ctrl->map[offset / SC_PER_PAGE]; 72 sc = page_address(mappage); 73 return sc + offset % SC_PER_PAGE; 74 } 75 76 static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent, 77 struct swap_cgroup_ctrl **ctrlp) 78 { 79 pgoff_t offset = swp_offset(ent); 80 struct swap_cgroup_ctrl *ctrl; 81 82 ctrl = &swap_cgroup_ctrl[swp_type(ent)]; 83 if (ctrlp) 84 *ctrlp = ctrl; 85 return __lookup_swap_cgroup(ctrl, offset); 86 } 87 88 /** 89 * swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry. 90 * @ent: swap entry to be cmpxchged 91 * @old: old id 92 * @new: new id 93 * 94 * Returns old id at success, 0 at failure. 95 * (There is no mem_cgroup using 0 as its id) 96 */ 97 unsigned short swap_cgroup_cmpxchg(swp_entry_t ent, 98 unsigned short old, unsigned short new) 99 { 100 struct swap_cgroup_ctrl *ctrl; 101 struct swap_cgroup *sc; 102 unsigned long flags; 103 unsigned short retval; 104 105 sc = lookup_swap_cgroup(ent, &ctrl); 106 107 spin_lock_irqsave(&ctrl->lock, flags); 108 retval = sc->id; 109 if (retval == old) 110 sc->id = new; 111 else 112 retval = 0; 113 spin_unlock_irqrestore(&ctrl->lock, flags); 114 return retval; 115 } 116 117 /** 118 * swap_cgroup_record - record mem_cgroup for a set of swap entries 119 * @ent: the first swap entry to be recorded into 120 * @id: mem_cgroup to be recorded 121 * @nr_ents: number of swap entries to be recorded 122 * 123 * Returns old value at success, 0 at failure. 124 * (Of course, old value can be 0.) 125 */ 126 unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id, 127 unsigned int nr_ents) 128 { 129 struct swap_cgroup_ctrl *ctrl; 130 struct swap_cgroup *sc; 131 unsigned short old; 132 unsigned long flags; 133 pgoff_t offset = swp_offset(ent); 134 pgoff_t end = offset + nr_ents; 135 136 sc = lookup_swap_cgroup(ent, &ctrl); 137 138 spin_lock_irqsave(&ctrl->lock, flags); 139 old = sc->id; 140 for (;;) { 141 VM_BUG_ON(sc->id != old); 142 sc->id = id; 143 offset++; 144 if (offset == end) 145 break; 146 if (offset % SC_PER_PAGE) 147 sc++; 148 else 149 sc = __lookup_swap_cgroup(ctrl, offset); 150 } 151 spin_unlock_irqrestore(&ctrl->lock, flags); 152 153 return old; 154 } 155 156 /** 157 * lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry 158 * @ent: swap entry to be looked up. 159 * 160 * Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID) 161 */ 162 unsigned short lookup_swap_cgroup_id(swp_entry_t ent) 163 { 164 return lookup_swap_cgroup(ent, NULL)->id; 165 } 166 167 int swap_cgroup_swapon(int type, unsigned long max_pages) 168 { 169 void *array; 170 unsigned long length; 171 struct swap_cgroup_ctrl *ctrl; 172 173 length = DIV_ROUND_UP(max_pages, SC_PER_PAGE); 174 175 array = vcalloc(length, sizeof(void *)); 176 if (!array) 177 goto nomem; 178 179 ctrl = &swap_cgroup_ctrl[type]; 180 mutex_lock(&swap_cgroup_mutex); 181 ctrl->length = length; 182 ctrl->map = array; 183 spin_lock_init(&ctrl->lock); 184 if (swap_cgroup_prepare(type)) { 185 /* memory shortage */ 186 ctrl->map = NULL; 187 ctrl->length = 0; 188 mutex_unlock(&swap_cgroup_mutex); 189 vfree(array); 190 goto nomem; 191 } 192 mutex_unlock(&swap_cgroup_mutex); 193 194 return 0; 195 nomem: 196 pr_info("couldn't allocate enough memory for swap_cgroup\n"); 197 pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n"); 198 return -ENOMEM; 199 } 200 201 void swap_cgroup_swapoff(int type) 202 { 203 struct page **map; 204 unsigned long i, length; 205 struct swap_cgroup_ctrl *ctrl; 206 207 mutex_lock(&swap_cgroup_mutex); 208 ctrl = &swap_cgroup_ctrl[type]; 209 map = ctrl->map; 210 length = ctrl->length; 211 ctrl->map = NULL; 212 ctrl->length = 0; 213 mutex_unlock(&swap_cgroup_mutex); 214 215 if (map) { 216 for (i = 0; i < length; i++) { 217 struct page *page = map[i]; 218 if (page) 219 __free_page(page); 220 if (!(i % SWAP_CLUSTER_MAX)) 221 cond_resched(); 222 } 223 vfree(map); 224 } 225 } 226