Quelle page_reporting.c Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/page_reporting.h>
#include <linux/gfp.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/scatterlist.h>

#include "page_reporting.h"
#include "internal.h"

/* Initialize to an unsupported value */
unsigned int page_reporting_order = -1;

static int page_order_update_notify(const char *val, const struct kernel_param *kp)
{
/*
* If param is set beyond this limit, order is set to default
* pageblock_order value
*/
return  param_set_uint_minmax(val, kp, 0, MAX_PAGE_ORDER);
}

static const struct kernel_param_ops page_reporting_param_ops = {
.set = &page_order_update_notify,
/*
* For the get op, use param_get_int instead of param_get_uint.
* This is to make sure that when unset the initialized value of
* -1 is shown correctly
*/
.get = ¶m_get_int,
};

module_param_cb(page_reporting_order, &page_reporting_param_ops,
   &page_reporting_order, 0644);
MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");

/*
* This symbol is also a kernel parameter. Export the page_reporting_order
* symbol so that other drivers can access it to control order values without
* having to introduce another configurable parameter. Only one driver can
* register with the page_reporting driver for the service, so we have just
* one control parameter for the use case(which can be accessed in both
* drivers)
*/
EXPORT_SYMBOL_GPL(page_reporting_order);

#define PAGE_REPORTING_DELAY (2 * HZ)
static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;

enum {
PAGE_REPORTING_IDLE = 0,
PAGE_REPORTING_REQUESTED,
PAGE_REPORTING_ACTIVE
};

/* request page reporting */
static void
__page_reporting_request(struct page_reporting_dev_info *prdev)
{
unsigned int state;

/* Check to see if we are in desired state */
state = atomic_read(&prdev->state);
if (state == PAGE_REPORTING_REQUESTED)
  return;

/*
* If reporting is already active there is nothing we need to do.
* Test against 0 as that represents PAGE_REPORTING_IDLE.
*/
state = atomic_xchg(&prdev->state, PAGE_REPORTING_REQUESTED);
if (state != PAGE_REPORTING_IDLE)
  return;

/*
* Delay the start of work to allow a sizable queue to build. For
* now we are limiting this to running no more than once every
* couple of seconds.
*/
schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
}

/* notify prdev of free page reporting request */
void __page_reporting_notify(void)
{
struct page_reporting_dev_info *prdev;

/*
* We use RCU to protect the pr_dev_info pointer. In almost all
* cases this should be present, however in the unlikely case of
* a shutdown this will be NULL and we should exit.
*/
rcu_read_lock();
prdev = rcu_dereference(pr_dev_info);
if (likely(prdev))
  __page_reporting_request(prdev);

rcu_read_unlock();
}

static void
page_reporting_drain(struct page_reporting_dev_info *prdev,
       struct scatterlist *sgl, unsigned int nents, bool reported)
{
struct scatterlist *sg = sgl;

/*
* Drain the now reported pages back into their respective
* free lists/areas. We assume at least one page is populated.
*/
do {
  struct page *page = sg_page(sg);
  int mt = get_pageblock_migratetype(page);
  unsigned int order = get_order(sg->length);

  __putback_isolated_page(page, order, mt);

  /* If the pages were not reported due to error skip flagging */
  if (!reported)
   continue;

  /*
* If page was not comingled with another page we can
* consider the result to be "reported" since the page
* hasn't been modified, otherwise we will need to
* report on the new larger page when we make our way
* up to that higher order.
*/
  if (PageBuddy(page) && buddy_order(page) == order)
   __SetPageReported(page);
} while ((sg = sg_next(sg)));

/* reinitialize scatterlist now that it is empty */
sg_init_table(sgl, nents);
}

/*
* The page reporting cycle consists of 4 stages, fill, report, drain, and
* idle. We will cycle through the first 3 stages until we cannot obtain a
* full scatterlist of pages, in that case we will switch to idle.
*/
static int
page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
       unsigned int order, unsigned int mt,
       struct scatterlist *sgl, unsigned int *offset)
{
struct free_area *area = &zone->free_area[order];
struct list_head *list = &area->free_list[mt];
unsigned int page_len = PAGE_SIZE << order;
struct page *page, *next;
long budget;
int err = 0;

/*
* Perform early check, if free area is empty there is
* nothing to process so we can skip this free_list.
*/
if (list_empty(list))
  return err;

spin_lock_irq(&zone->lock);

/*
* Limit how many calls we will be making to the page reporting
* device for this list. By doing this we avoid processing any
* given list for too long.
*
* The current value used allows us enough calls to process over a
* sixteenth of the current list plus one additional call to handle
* any pages that may have already been present from the previous
* list processed. This should result in us reporting all pages on
* an idle system in about 30 seconds.
*
* The division here should be cheap since PAGE_REPORTING_CAPACITY
* should always be a power of 2.
*/
budget = DIV_ROUND_UP(area->nr_free, PAGE_REPORTING_CAPACITY * 16);

/* loop through free list adding unreported pages to sg list */
list_for_each_entry_safe(page, next, list, lru) {
  /* We are going to skip over the reported pages. */
  if (PageReported(page))
   continue;

  /*
* If we fully consumed our budget then update our
* state to indicate that we are requesting additional
* processing and exit this list.
*/
  if (budget < 0) {
   atomic_set(&prdev->state, PAGE_REPORTING_REQUESTED);
   next = page;
   break;
  }

  /* Attempt to pull page from list and place in scatterlist */
  if (*offset) {
   if (!__isolate_free_page(page, order)) {
    next = page;
    break;
   }

   /* Add page to scatter list */
   --(*offset);
   sg_set_page(&sgl[*offset], page, page_len, 0);

   continue;
  }

  /*
* Make the first non-reported page in the free list
* the new head of the free list before we release the
* zone lock.
*/
  if (!list_is_first(&page->lru, list))
   list_rotate_to_front(&page->lru, list);

  /* release lock before waiting on report processing */
  spin_unlock_irq(&zone->lock);

  /* begin processing pages in local list */
  err = prdev->report(prdev, sgl, PAGE_REPORTING_CAPACITY);

  /* reset offset since the full list was reported */
  *offset = PAGE_REPORTING_CAPACITY;

  /* update budget to reflect call to report function */
  budget--;

  /* reacquire zone lock and resume processing */
  spin_lock_irq(&zone->lock);

  /* flush reported pages from the sg list */
  page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, !err);

  /*
* Reset next to first entry, the old next isn't valid
* since we dropped the lock to report the pages
*/
  next = list_first_entry(list, struct page, lru);

  /* exit on error */
  if (err)
   break;
}

/* Rotate any leftover pages to the head of the freelist */
if (!list_entry_is_head(next, list, lru) && !list_is_first(&next->lru, list))
  list_rotate_to_front(&next->lru, list);

spin_unlock_irq(&zone->lock);

return err;
}

static int
page_reporting_process_zone(struct page_reporting_dev_info *prdev,
       struct scatterlist *sgl, struct zone *zone)
{
unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY;
unsigned long watermark;
int err = 0;

/* Generate minimum watermark to be able to guarantee progress */
watermark = low_wmark_pages(zone) +
      (PAGE_REPORTING_CAPACITY << page_reporting_order);

/*
* Cancel request if insufficient free memory or if we failed
* to allocate page reporting statistics for the zone.
*/
if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
  return err;

/* Process each free list starting from lowest order/mt */
for (order = page_reporting_order; order < NR_PAGE_ORDERS; order++) {
  for (mt = 0; mt < MIGRATE_TYPES; mt++) {
   /* We do not pull pages from the isolate free list */
   if (is_migrate_isolate(mt))
    continue;

   err = page_reporting_cycle(prdev, zone, order, mt,
         sgl, &offset);
   if (err)
    return err;
  }
}

/* report the leftover pages before going idle */
leftover = PAGE_REPORTING_CAPACITY - offset;
if (leftover) {
  sgl = &sgl[offset];
  err = prdev->report(prdev, sgl, leftover);

  /* flush any remaining pages out from the last report */
  spin_lock_irq(&zone->lock);
  page_reporting_drain(prdev, sgl, leftover, !err);
  spin_unlock_irq(&zone->lock);
}

return err;
}

static void page_reporting_process(struct work_struct *work)
{
struct delayed_work *d_work = to_delayed_work(work);
struct page_reporting_dev_info *prdev =
  container_of(d_work, struct page_reporting_dev_info, work);
int err = 0, state = PAGE_REPORTING_ACTIVE;
struct scatterlist *sgl;
struct zone *zone;

/*
* Change the state to "Active" so that we can track if there is
* anyone requests page reporting after we complete our pass. If
* the state is not altered by the end of the pass we will switch
* to idle and quit scheduling reporting runs.
*/
atomic_set(&prdev->state, state);

/* allocate scatterlist to store pages being reported on */
sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, sizeof(*sgl), GFP_KERNEL);
if (!sgl)
  goto err_out;

sg_init_table(sgl, PAGE_REPORTING_CAPACITY);

for_each_zone(zone) {
  err = page_reporting_process_zone(prdev, sgl, zone);
  if (err)
   break;
}

kfree(sgl);
err_out:
/*
* If the state has reverted back to requested then there may be
* additional pages to be processed. We will defer for 2s to allow
* more pages to accumulate.
*/
state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE);
if (state == PAGE_REPORTING_REQUESTED)
  schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
}

static DEFINE_MUTEX(page_reporting_mutex);
DEFINE_STATIC_KEY_FALSE(page_reporting_enabled);

int page_reporting_register(struct page_reporting_dev_info *prdev)
{
int err = 0;

mutex_lock(&page_reporting_mutex);

/* nothing to do if already in use */
if (rcu_dereference_protected(pr_dev_info,
    lockdep_is_held(&page_reporting_mutex))) {
  err = -EBUSY;
  goto err_out;
}

/*
* If the page_reporting_order value is not set, we check if
* an order is provided from the driver that is performing the
* registration. If that is not provided either, we default to
* pageblock_order.
*/

if (page_reporting_order == -1) {
  if (prdev->order > 0 && prdev->order <= MAX_PAGE_ORDER)
   page_reporting_order = prdev->order;
  else
   page_reporting_order = pageblock_order;
}

/* initialize state and work structures */
atomic_set(&prdev->state, PAGE_REPORTING_IDLE);
INIT_DELAYED_WORK(&prdev->work, &page_reporting_process);

/* Begin initial flush of zones */
__page_reporting_request(prdev);

/* Assign device to allow notifications */
rcu_assign_pointer(pr_dev_info, prdev);

/* enable page reporting notification */
if (!static_key_enabled(&page_reporting_enabled)) {
  static_branch_enable(&page_reporting_enabled);
  pr_info("Free page reporting enabled\n");
}
err_out:
mutex_unlock(&page_reporting_mutex);

return err;
}
EXPORT_SYMBOL_GPL(page_reporting_register);

void page_reporting_unregister(struct page_reporting_dev_info *prdev)
{
mutex_lock(&page_reporting_mutex);

if (prdev == rcu_dereference_protected(pr_dev_info,
    lockdep_is_held(&page_reporting_mutex))) {
  /* Disable page reporting notification */
  RCU_INIT_POINTER(pr_dev_info, NULL);
  synchronize_rcu();

  /* Flush any existing work, and lock it out */
  cancel_delayed_work_sync(&prdev->work);
}

mutex_unlock(&page_reporting_mutex);
}
EXPORT_SYMBOL_GPL(page_reporting_unregister);

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