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![Gavin Shan](/assets/img/avatar_default.png)
The page reporting order (threshold) is sticky to @pageblock_order by default. The page reporting can never be triggered because the freeing page can't come up with a free area like that huge. The situation becomes worse when the system memory becomes heavily fragmented. For example, the following configurations are used on ARM64 when 64KB base page size is enabled. In this specific case, the page reporting won't be triggered until the freeing page comes up with a 512MB free area. That's hard to be met, especially when the system memory becomes heavily fragmented. PAGE_SIZE: 64KB HPAGE_SIZE: 512MB pageblock_order: 13 (512MB) MAX_ORDER: 14 This allows the drivers to specify the page reporting order when the page reporting device is registered. It falls back to @pageblock_order if it's not specified by the driver. The existing users (hv_balloon and virtio_balloon) don't specify it and @pageblock_order is still taken as their page reporting order. So this shouldn't introduce any functional changes. Link: https://lkml.kernel.org/r/20210625014710.42954-4-gshan@redhat.com Signed-off-by: Gavin Shan <gshan@redhat.com> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
375 lines
10 KiB
C
375 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/page_reporting.h>
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#include <linux/gfp.h>
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#include <linux/export.h>
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#include <linux/module.h>
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#include <linux/delay.h>
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#include <linux/scatterlist.h>
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#include "page_reporting.h"
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#include "internal.h"
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unsigned int page_reporting_order = MAX_ORDER;
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module_param(page_reporting_order, uint, 0644);
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MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
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#define PAGE_REPORTING_DELAY (2 * HZ)
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static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
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enum {
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PAGE_REPORTING_IDLE = 0,
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PAGE_REPORTING_REQUESTED,
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PAGE_REPORTING_ACTIVE
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};
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/* request page reporting */
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static void
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__page_reporting_request(struct page_reporting_dev_info *prdev)
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{
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unsigned int state;
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/* Check to see if we are in desired state */
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state = atomic_read(&prdev->state);
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if (state == PAGE_REPORTING_REQUESTED)
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return;
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/*
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* If reporting is already active there is nothing we need to do.
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* Test against 0 as that represents PAGE_REPORTING_IDLE.
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*/
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state = atomic_xchg(&prdev->state, PAGE_REPORTING_REQUESTED);
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if (state != PAGE_REPORTING_IDLE)
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return;
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/*
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* Delay the start of work to allow a sizable queue to build. For
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* now we are limiting this to running no more than once every
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* couple of seconds.
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*/
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schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
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}
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/* notify prdev of free page reporting request */
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void __page_reporting_notify(void)
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{
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struct page_reporting_dev_info *prdev;
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/*
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* We use RCU to protect the pr_dev_info pointer. In almost all
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* cases this should be present, however in the unlikely case of
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* a shutdown this will be NULL and we should exit.
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*/
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rcu_read_lock();
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prdev = rcu_dereference(pr_dev_info);
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if (likely(prdev))
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__page_reporting_request(prdev);
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rcu_read_unlock();
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}
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static void
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page_reporting_drain(struct page_reporting_dev_info *prdev,
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struct scatterlist *sgl, unsigned int nents, bool reported)
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{
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struct scatterlist *sg = sgl;
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/*
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* Drain the now reported pages back into their respective
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* free lists/areas. We assume at least one page is populated.
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*/
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do {
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struct page *page = sg_page(sg);
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int mt = get_pageblock_migratetype(page);
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unsigned int order = get_order(sg->length);
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__putback_isolated_page(page, order, mt);
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/* If the pages were not reported due to error skip flagging */
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if (!reported)
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continue;
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/*
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* If page was not comingled with another page we can
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* consider the result to be "reported" since the page
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* hasn't been modified, otherwise we will need to
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* report on the new larger page when we make our way
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* up to that higher order.
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*/
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if (PageBuddy(page) && buddy_order(page) == order)
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__SetPageReported(page);
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} while ((sg = sg_next(sg)));
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/* reinitialize scatterlist now that it is empty */
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sg_init_table(sgl, nents);
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}
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/*
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* The page reporting cycle consists of 4 stages, fill, report, drain, and
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* idle. We will cycle through the first 3 stages until we cannot obtain a
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* full scatterlist of pages, in that case we will switch to idle.
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*/
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static int
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page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
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unsigned int order, unsigned int mt,
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struct scatterlist *sgl, unsigned int *offset)
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{
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struct free_area *area = &zone->free_area[order];
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struct list_head *list = &area->free_list[mt];
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unsigned int page_len = PAGE_SIZE << order;
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struct page *page, *next;
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long budget;
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int err = 0;
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/*
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* Perform early check, if free area is empty there is
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* nothing to process so we can skip this free_list.
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*/
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if (list_empty(list))
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return err;
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spin_lock_irq(&zone->lock);
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/*
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* Limit how many calls we will be making to the page reporting
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* device for this list. By doing this we avoid processing any
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* given list for too long.
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*
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* The current value used allows us enough calls to process over a
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* sixteenth of the current list plus one additional call to handle
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* any pages that may have already been present from the previous
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* list processed. This should result in us reporting all pages on
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* an idle system in about 30 seconds.
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*
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* The division here should be cheap since PAGE_REPORTING_CAPACITY
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* should always be a power of 2.
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*/
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budget = DIV_ROUND_UP(area->nr_free, PAGE_REPORTING_CAPACITY * 16);
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/* loop through free list adding unreported pages to sg list */
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list_for_each_entry_safe(page, next, list, lru) {
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/* We are going to skip over the reported pages. */
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if (PageReported(page))
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continue;
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/*
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* If we fully consumed our budget then update our
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* state to indicate that we are requesting additional
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* processing and exit this list.
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*/
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if (budget < 0) {
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atomic_set(&prdev->state, PAGE_REPORTING_REQUESTED);
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next = page;
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break;
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}
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/* Attempt to pull page from list and place in scatterlist */
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if (*offset) {
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if (!__isolate_free_page(page, order)) {
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next = page;
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break;
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}
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/* Add page to scatter list */
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--(*offset);
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sg_set_page(&sgl[*offset], page, page_len, 0);
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continue;
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}
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/*
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* Make the first non-reported page in the free list
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* the new head of the free list before we release the
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* zone lock.
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*/
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if (!list_is_first(&page->lru, list))
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list_rotate_to_front(&page->lru, list);
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/* release lock before waiting on report processing */
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spin_unlock_irq(&zone->lock);
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/* begin processing pages in local list */
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err = prdev->report(prdev, sgl, PAGE_REPORTING_CAPACITY);
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/* reset offset since the full list was reported */
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*offset = PAGE_REPORTING_CAPACITY;
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/* update budget to reflect call to report function */
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budget--;
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/* reacquire zone lock and resume processing */
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spin_lock_irq(&zone->lock);
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/* flush reported pages from the sg list */
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page_reporting_drain(prdev, sgl, PAGE_REPORTING_CAPACITY, !err);
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/*
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* Reset next to first entry, the old next isn't valid
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* since we dropped the lock to report the pages
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*/
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next = list_first_entry(list, struct page, lru);
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/* exit on error */
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if (err)
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break;
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}
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/* Rotate any leftover pages to the head of the freelist */
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if (!list_entry_is_head(next, list, lru) && !list_is_first(&next->lru, list))
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list_rotate_to_front(&next->lru, list);
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spin_unlock_irq(&zone->lock);
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return err;
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}
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static int
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page_reporting_process_zone(struct page_reporting_dev_info *prdev,
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struct scatterlist *sgl, struct zone *zone)
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{
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unsigned int order, mt, leftover, offset = PAGE_REPORTING_CAPACITY;
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unsigned long watermark;
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int err = 0;
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/* Generate minimum watermark to be able to guarantee progress */
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watermark = low_wmark_pages(zone) +
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(PAGE_REPORTING_CAPACITY << page_reporting_order);
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/*
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* Cancel request if insufficient free memory or if we failed
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* to allocate page reporting statistics for the zone.
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*/
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if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
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return err;
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/* Process each free list starting from lowest order/mt */
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for (order = page_reporting_order; order < MAX_ORDER; order++) {
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for (mt = 0; mt < MIGRATE_TYPES; mt++) {
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/* We do not pull pages from the isolate free list */
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if (is_migrate_isolate(mt))
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continue;
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err = page_reporting_cycle(prdev, zone, order, mt,
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sgl, &offset);
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if (err)
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return err;
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}
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}
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/* report the leftover pages before going idle */
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leftover = PAGE_REPORTING_CAPACITY - offset;
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if (leftover) {
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sgl = &sgl[offset];
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err = prdev->report(prdev, sgl, leftover);
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/* flush any remaining pages out from the last report */
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spin_lock_irq(&zone->lock);
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page_reporting_drain(prdev, sgl, leftover, !err);
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spin_unlock_irq(&zone->lock);
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}
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return err;
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}
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static void page_reporting_process(struct work_struct *work)
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{
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struct delayed_work *d_work = to_delayed_work(work);
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struct page_reporting_dev_info *prdev =
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container_of(d_work, struct page_reporting_dev_info, work);
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int err = 0, state = PAGE_REPORTING_ACTIVE;
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struct scatterlist *sgl;
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struct zone *zone;
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/*
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* Change the state to "Active" so that we can track if there is
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* anyone requests page reporting after we complete our pass. If
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* the state is not altered by the end of the pass we will switch
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* to idle and quit scheduling reporting runs.
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*/
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atomic_set(&prdev->state, state);
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/* allocate scatterlist to store pages being reported on */
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sgl = kmalloc_array(PAGE_REPORTING_CAPACITY, sizeof(*sgl), GFP_KERNEL);
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if (!sgl)
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goto err_out;
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sg_init_table(sgl, PAGE_REPORTING_CAPACITY);
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for_each_zone(zone) {
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err = page_reporting_process_zone(prdev, sgl, zone);
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if (err)
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break;
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}
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kfree(sgl);
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err_out:
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/*
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* If the state has reverted back to requested then there may be
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* additional pages to be processed. We will defer for 2s to allow
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* more pages to accumulate.
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*/
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state = atomic_cmpxchg(&prdev->state, state, PAGE_REPORTING_IDLE);
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if (state == PAGE_REPORTING_REQUESTED)
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schedule_delayed_work(&prdev->work, PAGE_REPORTING_DELAY);
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}
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static DEFINE_MUTEX(page_reporting_mutex);
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DEFINE_STATIC_KEY_FALSE(page_reporting_enabled);
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int page_reporting_register(struct page_reporting_dev_info *prdev)
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{
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int err = 0;
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mutex_lock(&page_reporting_mutex);
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/* nothing to do if already in use */
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if (rcu_access_pointer(pr_dev_info)) {
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err = -EBUSY;
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goto err_out;
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}
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/*
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* Update the page reporting order if it's specified by driver.
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* Otherwise, it falls back to @pageblock_order.
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*/
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page_reporting_order = prdev->order ? : pageblock_order;
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/* initialize state and work structures */
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atomic_set(&prdev->state, PAGE_REPORTING_IDLE);
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INIT_DELAYED_WORK(&prdev->work, &page_reporting_process);
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/* Begin initial flush of zones */
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__page_reporting_request(prdev);
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/* Assign device to allow notifications */
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rcu_assign_pointer(pr_dev_info, prdev);
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/* enable page reporting notification */
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if (!static_key_enabled(&page_reporting_enabled)) {
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static_branch_enable(&page_reporting_enabled);
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pr_info("Free page reporting enabled\n");
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}
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err_out:
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mutex_unlock(&page_reporting_mutex);
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return err;
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}
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EXPORT_SYMBOL_GPL(page_reporting_register);
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void page_reporting_unregister(struct page_reporting_dev_info *prdev)
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{
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mutex_lock(&page_reporting_mutex);
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if (rcu_access_pointer(pr_dev_info) == prdev) {
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/* Disable page reporting notification */
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RCU_INIT_POINTER(pr_dev_info, NULL);
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synchronize_rcu();
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/* Flush any existing work, and lock it out */
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cancel_delayed_work_sync(&prdev->work);
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}
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mutex_unlock(&page_reporting_mutex);
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}
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EXPORT_SYMBOL_GPL(page_reporting_unregister);
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