1// SPDX-License-Identifier: GPL-2.0
2#include <linux/mm.h>
3#include <linux/mmzone.h>
4#include <linux/page_reporting.h>
5#include <linux/gfp.h>
6#include <linux/export.h>
7#include <linux/module.h>
8#include <linux/delay.h>
9#include <linux/scatterlist.h>
10
11#include "page_reporting.h"
12#include "internal.h"
13
14/* Initialize to an unsupported value */
15unsigned int page_reporting_order = -1;
16
17static int page_order_update_notify(const char *val, const struct kernel_param *kp)
18{
19 /*
20 * If param is set beyond this limit, order is set to default
21 * pageblock_order value
22 */
23 return param_set_uint_minmax(val, kp, min: 0, MAX_ORDER);
24}
25
26static const struct kernel_param_ops page_reporting_param_ops = {
27 .set = &page_order_update_notify,
28 /*
29 * For the get op, use param_get_int instead of param_get_uint.
30 * This is to make sure that when unset the initialized value of
31 * -1 is shown correctly
32 */
33 .get = &param_get_int,
34};
35
36module_param_cb(page_reporting_order, &page_reporting_param_ops,
37 &page_reporting_order, 0644);
38MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
39
40/*
41 * This symbol is also a kernel parameter. Export the page_reporting_order
42 * symbol so that other drivers can access it to control order values without
43 * having to introduce another configurable parameter. Only one driver can
44 * register with the page_reporting driver for the service, so we have just
45 * one control parameter for the use case(which can be accessed in both
46 * drivers)
47 */
48EXPORT_SYMBOL_GPL(page_reporting_order);
49
50#define PAGE_REPORTING_DELAY (2 * HZ)
51static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
52
53enum {
54 PAGE_REPORTING_IDLE = 0,
55 PAGE_REPORTING_REQUESTED,
56 PAGE_REPORTING_ACTIVE
57};
58
59/* request page reporting */
60static void
61__page_reporting_request(struct page_reporting_dev_info *prdev)
62{
63 unsigned int state;
64
65 /* Check to see if we are in desired state */
66 state = atomic_read(v: &prdev->state);
67 if (state == PAGE_REPORTING_REQUESTED)
68 return;
69
70 /*
71 * If reporting is already active there is nothing we need to do.
72 * Test against 0 as that represents PAGE_REPORTING_IDLE.
73 */
74 state = atomic_xchg(v: &prdev->state, new: PAGE_REPORTING_REQUESTED);
75 if (state != PAGE_REPORTING_IDLE)
76 return;
77
78 /*
79 * Delay the start of work to allow a sizable queue to build. For
80 * now we are limiting this to running no more than once every
81 * couple of seconds.
82 */
83 schedule_delayed_work(dwork: &prdev->work, PAGE_REPORTING_DELAY);
84}
85
86/* notify prdev of free page reporting request */
87void __page_reporting_notify(void)
88{
89 struct page_reporting_dev_info *prdev;
90
91 /*
92 * We use RCU to protect the pr_dev_info pointer. In almost all
93 * cases this should be present, however in the unlikely case of
94 * a shutdown this will be NULL and we should exit.
95 */
96 rcu_read_lock();
97 prdev = rcu_dereference(pr_dev_info);
98 if (likely(prdev))
99 __page_reporting_request(prdev);
100
101 rcu_read_unlock();
102}
103
104static void
105page_reporting_drain(struct page_reporting_dev_info *prdev,
106 struct scatterlist *sgl, unsigned int nents, bool reported)
107{
108 struct scatterlist *sg = sgl;
109
110 /*
111 * Drain the now reported pages back into their respective
112 * free lists/areas. We assume at least one page is populated.
113 */
114 do {
115 struct page *page = sg_page(sg);
116 int mt = get_pageblock_migratetype(page);
117 unsigned int order = get_order(size: sg->length);
118
119 __putback_isolated_page(page, order, mt);
120
121 /* If the pages were not reported due to error skip flagging */
122 if (!reported)
123 continue;
124
125 /*
126 * If page was not comingled with another page we can
127 * consider the result to be "reported" since the page
128 * hasn't been modified, otherwise we will need to
129 * report on the new larger page when we make our way
130 * up to that higher order.
131 */
132 if (PageBuddy(page) && buddy_order(page) == order)
133 __SetPageReported(page);
134 } while ((sg = sg_next(sg)));
135
136 /* reinitialize scatterlist now that it is empty */
137 sg_init_table(sgl, nents);
138}
139
140/*
141 * The page reporting cycle consists of 4 stages, fill, report, drain, and
142 * idle. We will cycle through the first 3 stages until we cannot obtain a
143 * full scatterlist of pages, in that case we will switch to idle.
144 */
145static int
146page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
147 unsigned int order, unsigned int mt,
148 struct scatterlist *sgl, unsigned int *offset)
149{
150 struct free_area *area = &zone->free_area[order];
151 struct list_head *list = &area->free_list[mt];
152 unsigned int page_len = PAGE_SIZE << order;
153 struct page *page, *next;
154 long budget;
155 int err = 0;
156
157 /*
158 * Perform early check, if free area is empty there is
159 * nothing to process so we can skip this free_list.
160 */
161 if (list_empty(head: list))
162 return err;
163
164 spin_lock_irq(lock: &zone->lock);
165
166 /*
167 * Limit how many calls we will be making to the page reporting
168 * device for this list. By doing this we avoid processing any
169 * given list for too long.
170 *
171 * The current value used allows us enough calls to process over a
172 * sixteenth of the current list plus one additional call to handle
173 * any pages that may have already been present from the previous
174 * list processed. This should result in us reporting all pages on
175 * an idle system in about 30 seconds.
176 *
177 * The division here should be cheap since PAGE_REPORTING_CAPACITY
178 * should always be a power of 2.
179 */
180 budget = DIV_ROUND_UP(area->nr_free, PAGE_REPORTING_CAPACITY * 16);
181
182 /* loop through free list adding unreported pages to sg list */
183 list_for_each_entry_safe(page, next, list, lru) {
184 /* We are going to skip over the reported pages. */
185 if (PageReported(page))
186 continue;
187
188 /*
189 * If we fully consumed our budget then update our
190 * state to indicate that we are requesting additional
191 * processing and exit this list.
192 */
193 if (budget < 0) {
194 atomic_set(v: &prdev->state, i: PAGE_REPORTING_REQUESTED);
195 next = page;
196 break;
197 }
198
199 /* Attempt to pull page from list and place in scatterlist */
200 if (*offset) {
201 if (!__isolate_free_page(page, order)) {
202 next = page;
203 break;
204 }
205
206 /* Add page to scatter list */
207 --(*offset);
208 sg_set_page(sg: &sgl[*offset], page, len: page_len, offset: 0);
209
210 continue;
211 }
212
213 /*
214 * Make the first non-reported page in the free list
215 * the new head of the free list before we release the
216 * zone lock.
217 */
218 if (!list_is_first(list: &page->lru, head: list))
219 list_rotate_to_front(list: &page->lru, head: list);
220
221 /* release lock before waiting on report processing */
222 spin_unlock_irq(lock: &zone->lock);
223
224 /* begin processing pages in local list */
225 err = prdev->report(prdev, sgl, PAGE_REPORTING_CAPACITY);
226
227 /* reset offset since the full list was reported */
228 *offset = PAGE_REPORTING_CAPACITY;
229
230 /* update budget to reflect call to report function */
231 budget--;
232
233 /* reacquire zone lock and resume processing */
234 spin_lock_irq(lock: &zone->lock);
235
236 /* flush reported pages from the sg list */
237 page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, reported: !err);
238
239 /*
240 * Reset next to first entry, the old next isn't valid
241 * since we dropped the lock to report the pages
242 */
243 next = list_first_entry(list, struct page, lru);
244
245 /* exit on error */
246 if (err)
247 break;
248 }
249
250 /* Rotate any leftover pages to the head of the freelist */
251 if (!list_entry_is_head(next, list, lru) && !list_is_first(list: &next->lru, head: list))
252 list_rotate_to_front(list: &next->lru, head: list);
253
254 spin_unlock_irq(lock: &zone->lock);
255
256 return err;
257}
258
259static int
260page_reporting_process_zone(struct page_reporting_dev_info *prdev,
261 struct scatterlist *sgl, struct zone *zone)
262{
263 unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY;
264 unsigned long watermark;
265 int err = 0;
266
267 /* Generate minimum watermark to be able to guarantee progress */
268 watermark = low_wmark_pages(zone) +
269 (PAGE_REPORTING_CAPACITY << page_reporting_order);
270
271 /*
272 * Cancel request if insufficient free memory or if we failed
273 * to allocate page reporting statistics for the zone.
274 */
275 if (!zone_watermark_ok(z: zone, order: 0, mark: watermark, highest_zoneidx: 0, ALLOC_CMA))
276 return err;
277
278 /* Process each free list starting from lowest order/mt */
279 for (order = page_reporting_order; order <= MAX_ORDER; order++) {
280 for (mt = 0; mt < MIGRATE_TYPES; mt++) {
281 /* We do not pull pages from the isolate free list */
282 if (is_migrate_isolate(migratetype: mt))
283 continue;
284
285 err = page_reporting_cycle(prdev, zone, order, mt,
286 sgl, offset: &offset);
287 if (err)
288 return err;
289 }
290 }
291
292 /* report the leftover pages before going idle */
293 leftover = PAGE_REPORTING_CAPACITY - offset;
294 if (leftover) {
295 sgl = &sgl[offset];
296 err = prdev->report(prdev, sgl, leftover);
297
298 /* flush any remaining pages out from the last report */
299 spin_lock_irq(lock: &zone->lock);
300 page_reporting_drain(prdev, sgl, nents: leftover, reported: !err);
301 spin_unlock_irq(lock: &zone->lock);
302 }
303
304 return err;
305}
306
307static void page_reporting_process(struct work_struct *work)
308{
309 struct delayed_work *d_work = to_delayed_work(work);
310 struct page_reporting_dev_info *prdev =
311 container_of(d_work, struct page_reporting_dev_info, work);
312 int err = 0, state = PAGE_REPORTING_ACTIVE;
313 struct scatterlist *sgl;
314 struct zone *zone;
315
316 /*
317 * Change the state to "Active" so that we can track if there is
318 * anyone requests page reporting after we complete our pass. If
319 * the state is not altered by the end of the pass we will switch
320 * to idle and quit scheduling reporting runs.
321 */
322 atomic_set(v: &prdev->state, i: state);
323
324 /* allocate scatterlist to store pages being reported on */
325 sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, size: sizeof(*sgl), GFP_KERNEL);
326 if (!sgl)
327 goto err_out;
328
329 sg_init_table(sgl, PAGE_REPORTING_CAPACITY);
330
331 for_each_zone(zone) {
332 err = page_reporting_process_zone(prdev, sgl, zone);
333 if (err)
334 break;
335 }
336
337 kfree(objp: sgl);
338err_out:
339 /*
340 * If the state has reverted back to requested then there may be
341 * additional pages to be processed. We will defer for 2s to allow
342 * more pages to accumulate.
343 */
344 state = atomic_cmpxchg(v: &prdev->state, old: state, new: PAGE_REPORTING_IDLE);
345 if (state == PAGE_REPORTING_REQUESTED)
346 schedule_delayed_work(dwork: &prdev->work, PAGE_REPORTING_DELAY);
347}
348
349static DEFINE_MUTEX(page_reporting_mutex);
350DEFINE_STATIC_KEY_FALSE(page_reporting_enabled);
351
352int page_reporting_register(struct page_reporting_dev_info *prdev)
353{
354 int err = 0;
355
356 mutex_lock(&page_reporting_mutex);
357
358 /* nothing to do if already in use */
359 if (rcu_dereference_protected(pr_dev_info,
360 lockdep_is_held(&page_reporting_mutex))) {
361 err = -EBUSY;
362 goto err_out;
363 }
364
365 /*
366 * If the page_reporting_order value is not set, we check if
367 * an order is provided from the driver that is performing the
368 * registration. If that is not provided either, we default to
369 * pageblock_order.
370 */
371
372 if (page_reporting_order == -1) {
373 if (prdev->order > 0 && prdev->order <= MAX_ORDER)
374 page_reporting_order = prdev->order;
375 else
376 page_reporting_order = pageblock_order;
377 }
378
379 /* initialize state and work structures */
380 atomic_set(v: &prdev->state, i: PAGE_REPORTING_IDLE);
381 INIT_DELAYED_WORK(&prdev->work, &page_reporting_process);
382
383 /* Begin initial flush of zones */
384 __page_reporting_request(prdev);
385
386 /* Assign device to allow notifications */
387 rcu_assign_pointer(pr_dev_info, prdev);
388
389 /* enable page reporting notification */
390 if (!static_key_enabled(&page_reporting_enabled)) {
391 static_branch_enable(&page_reporting_enabled);
392 pr_info("Free page reporting enabled\n");
393 }
394err_out:
395 mutex_unlock(lock: &page_reporting_mutex);
396
397 return err;
398}
399EXPORT_SYMBOL_GPL(page_reporting_register);
400
401void page_reporting_unregister(struct page_reporting_dev_info *prdev)
402{
403 mutex_lock(&page_reporting_mutex);
404
405 if (prdev == rcu_dereference_protected(pr_dev_info,
406 lockdep_is_held(&page_reporting_mutex))) {
407 /* Disable page reporting notification */
408 RCU_INIT_POINTER(pr_dev_info, NULL);
409 synchronize_rcu();
410
411 /* Flush any existing work, and lock it out */
412 cancel_delayed_work_sync(dwork: &prdev->work);
413 }
414
415 mutex_unlock(lock: &page_reporting_mutex);
416}
417EXPORT_SYMBOL_GPL(page_reporting_unregister);
418

source code of linux/mm/page_reporting.c