Merge tag 'ntb-5.8' of git://github.com/jonmason/ntb
[platform/kernel/linux-rpi.git] / mm / swap_cgroup.c
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 array_size;
171         unsigned long length;
172         struct swap_cgroup_ctrl *ctrl;
173
174         length = DIV_ROUND_UP(max_pages, SC_PER_PAGE);
175         array_size = length * sizeof(void *);
176
177         array = vzalloc(array_size);
178         if (!array)
179                 goto nomem;
180
181         ctrl = &swap_cgroup_ctrl[type];
182         mutex_lock(&swap_cgroup_mutex);
183         ctrl->length = length;
184         ctrl->map = array;
185         spin_lock_init(&ctrl->lock);
186         if (swap_cgroup_prepare(type)) {
187                 /* memory shortage */
188                 ctrl->map = NULL;
189                 ctrl->length = 0;
190                 mutex_unlock(&swap_cgroup_mutex);
191                 vfree(array);
192                 goto nomem;
193         }
194         mutex_unlock(&swap_cgroup_mutex);
195
196         return 0;
197 nomem:
198         pr_info("couldn't allocate enough memory for swap_cgroup\n");
199         pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n");
200         return -ENOMEM;
201 }
202
203 void swap_cgroup_swapoff(int type)
204 {
205         struct page **map;
206         unsigned long i, length;
207         struct swap_cgroup_ctrl *ctrl;
208
209         mutex_lock(&swap_cgroup_mutex);
210         ctrl = &swap_cgroup_ctrl[type];
211         map = ctrl->map;
212         length = ctrl->length;
213         ctrl->map = NULL;
214         ctrl->length = 0;
215         mutex_unlock(&swap_cgroup_mutex);
216
217         if (map) {
218                 for (i = 0; i < length; i++) {
219                         struct page *page = map[i];
220                         if (page)
221                                 __free_page(page);
222                         if (!(i % SWAP_CLUSTER_MAX))
223                                 cond_resched();
224                 }
225                 vfree(map);
226         }
227 }