| 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 */ |
| 15 | unsigned int page_reporting_order = -1; |
| 16 | |
| 17 | static 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, 0, MAX_ORDER); |
| 24 | } |
| 25 | |
| 26 | static 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 = ¶m_get_int, |
| 34 | }; |
| 35 | |
| 36 | module_param_cb(page_reporting_order, &page_reporting_param_ops, |
| 37 | &page_reporting_order, 0644); |
| 38 | MODULE_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 | */ |
| 48 | EXPORT_SYMBOL_GPL(page_reporting_order); |
| 49 | |
| 50 | #define PAGE_REPORTING_DELAY (2 * HZ) |
| 51 | static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; |
| 52 | |
| 53 | enum { |
| 54 | PAGE_REPORTING_IDLE = 0, |
| 55 | PAGE_REPORTING_REQUESTED, |
| 56 | PAGE_REPORTING_ACTIVE |
| 57 | }; |
| 58 | |
| 59 | /* request page reporting */ |
| 60 | static 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(&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(&prdev->state, 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(&prdev->work, PAGE_REPORTING_DELAY); |
| 84 | } |
| 85 | |
| 86 | /* notify prdev of free page reporting request */ |
| 87 | void __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 | |
| 104 | static void |
| 105 | page_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(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 | */ |
| 145 | static int |
| 146 | page_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(list)) |
| 162 | return err; |
| 163 | |
| 164 | spin_lock_irq(&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(&prdev->state, 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(&sgl[*offset], page, page_len, 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(&page->lru, list)) |
| 219 | list_rotate_to_front(&page->lru, list); |
| 220 | |
| 221 | /* release lock before waiting on report processing */ |
| 222 | spin_unlock_irq(&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(&zone->lock); |
| 235 | |
| 236 | /* flush reported pages from the sg list */ |
| 237 | page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, !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(&next->lru, list)) |
| 252 | list_rotate_to_front(&next->lru, list); |
| 253 | |
| 254 | spin_unlock_irq(&zone->lock); |
| 255 | |
| 256 | return err; |
| 257 | } |
| 258 | |
| 259 | static int |
| 260 | page_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(zone, 0, watermark, 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(mt)) |
| 283 | continue; |
| 284 | |
| 285 | err = page_reporting_cycle(prdev, zone, order, mt, |
| 286 | sgl, &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(&zone->lock); |
| 300 | page_reporting_drain(prdev, sgl, leftover, !err); |
| 301 | spin_unlock_irq(&zone->lock); |
| 302 | } |
| 303 | |
| 304 | return err; |
| 305 | } |
| 306 | |
| 307 | static 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(&prdev->state, state); |
| 323 | |
| 324 | /* allocate scatterlist to store pages being reported on */ |
| 325 | sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, 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(sgl); |
| 338 | err_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(&prdev->state, state, PAGE_REPORTING_IDLE); |
| 345 | if (state == PAGE_REPORTING_REQUESTED) |
| 346 | schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY); |
| 347 | } |
| 348 | |
| 349 | static DEFINE_MUTEX(page_reporting_mutex); |
| 350 | DEFINE_STATIC_KEY_FALSE(page_reporting_enabled); |
| 351 | |
| 352 | int 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(&prdev->state, 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 | } |
| 394 | err_out: |
| 395 | mutex_unlock(&page_reporting_mutex); |
| 396 | |
| 397 | return err; |
| 398 | } |
| 399 | EXPORT_SYMBOL_GPL(page_reporting_register); |
| 400 | |
| 401 | void 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(&prdev->work); |
| 413 | } |
| 414 | |
| 415 | mutex_unlock(&page_reporting_mutex); |
| 416 | } |
| 417 | EXPORT_SYMBOL_GPL(page_reporting_unregister); |