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![Yang Li](/assets/img/avatar_default.png)
Remove one warning found by running scripts/kernel-doc, which is caused by using 'make W=1': mm/page_isolation.c:304: warning: Function parameter or member 'skip_isolation' not described in 'isolate_single_pageblock' Link: https://lkml.kernel.org/r/20220602062116.61199-1-yang.lee@linux.alibaba.com Signed-off-by: Yang Li <yang.lee@linux.alibaba.com> Reported-by: Abaci Robot <abaci@linux.alibaba.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
669 lines
21 KiB
C
669 lines
21 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/page_isolation.c
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*/
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#include <linux/mm.h>
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#include <linux/page-isolation.h>
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#include <linux/pageblock-flags.h>
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#include <linux/memory.h>
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#include <linux/hugetlb.h>
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#include <linux/page_owner.h>
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#include <linux/migrate.h>
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#include "internal.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/page_isolation.h>
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/*
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* This function checks whether the range [start_pfn, end_pfn) includes
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* unmovable pages or not. The range must fall into a single pageblock and
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* consequently belong to a single zone.
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*
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* PageLRU check without isolation or lru_lock could race so that
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* MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
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* check without lock_page also may miss some movable non-lru pages at
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* race condition. So you can't expect this function should be exact.
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*
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* Returns a page without holding a reference. If the caller wants to
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* dereference that page (e.g., dumping), it has to make sure that it
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* cannot get removed (e.g., via memory unplug) concurrently.
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*
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*/
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static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long end_pfn,
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int migratetype, int flags)
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{
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struct page *page = pfn_to_page(start_pfn);
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struct zone *zone = page_zone(page);
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unsigned long pfn;
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VM_BUG_ON(ALIGN_DOWN(start_pfn, pageblock_nr_pages) !=
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ALIGN_DOWN(end_pfn - 1, pageblock_nr_pages));
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if (is_migrate_cma_page(page)) {
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/*
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* CMA allocations (alloc_contig_range) really need to mark
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* isolate CMA pageblocks even when they are not movable in fact
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* so consider them movable here.
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*/
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if (is_migrate_cma(migratetype))
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return NULL;
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return page;
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}
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for (pfn = start_pfn; pfn < end_pfn; pfn++) {
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page = pfn_to_page(pfn);
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/*
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* Both, bootmem allocations and memory holes are marked
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* PG_reserved and are unmovable. We can even have unmovable
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* allocations inside ZONE_MOVABLE, for example when
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* specifying "movablecore".
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*/
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if (PageReserved(page))
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return page;
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/*
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* If the zone is movable and we have ruled out all reserved
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* pages then it should be reasonably safe to assume the rest
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* is movable.
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*/
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if (zone_idx(zone) == ZONE_MOVABLE)
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continue;
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/*
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* Hugepages are not in LRU lists, but they're movable.
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* THPs are on the LRU, but need to be counted as #small pages.
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* We need not scan over tail pages because we don't
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* handle each tail page individually in migration.
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*/
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if (PageHuge(page) || PageTransCompound(page)) {
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struct page *head = compound_head(page);
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unsigned int skip_pages;
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if (PageHuge(page)) {
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if (!hugepage_migration_supported(page_hstate(head)))
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return page;
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} else if (!PageLRU(head) && !__PageMovable(head)) {
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return page;
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}
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skip_pages = compound_nr(head) - (page - head);
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pfn += skip_pages - 1;
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continue;
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}
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/*
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* We can't use page_count without pin a page
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* because another CPU can free compound page.
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* This check already skips compound tails of THP
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* because their page->_refcount is zero at all time.
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*/
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if (!page_ref_count(page)) {
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if (PageBuddy(page))
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pfn += (1 << buddy_order(page)) - 1;
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continue;
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}
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/*
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* The HWPoisoned page may be not in buddy system, and
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* page_count() is not 0.
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*/
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if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
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continue;
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/*
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* We treat all PageOffline() pages as movable when offlining
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* to give drivers a chance to decrement their reference count
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* in MEM_GOING_OFFLINE in order to indicate that these pages
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* can be offlined as there are no direct references anymore.
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* For actually unmovable PageOffline() where the driver does
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* not support this, we will fail later when trying to actually
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* move these pages that still have a reference count > 0.
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* (false negatives in this function only)
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*/
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if ((flags & MEMORY_OFFLINE) && PageOffline(page))
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continue;
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if (__PageMovable(page) || PageLRU(page))
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continue;
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/*
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* If there are RECLAIMABLE pages, we need to check
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* it. But now, memory offline itself doesn't call
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* shrink_node_slabs() and it still to be fixed.
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*/
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return page;
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}
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return NULL;
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}
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/*
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* This function set pageblock migratetype to isolate if no unmovable page is
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* present in [start_pfn, end_pfn). The pageblock must intersect with
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* [start_pfn, end_pfn).
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*/
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static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags,
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unsigned long start_pfn, unsigned long end_pfn)
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{
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struct zone *zone = page_zone(page);
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struct page *unmovable;
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unsigned long flags;
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unsigned long check_unmovable_start, check_unmovable_end;
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spin_lock_irqsave(&zone->lock, flags);
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/*
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* We assume the caller intended to SET migrate type to isolate.
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* If it is already set, then someone else must have raced and
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* set it before us.
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*/
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if (is_migrate_isolate_page(page)) {
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spin_unlock_irqrestore(&zone->lock, flags);
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return -EBUSY;
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}
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/*
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* FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
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* We just check MOVABLE pages.
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*
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* Pass the intersection of [start_pfn, end_pfn) and the page's pageblock
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* to avoid redundant checks.
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*/
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check_unmovable_start = max(page_to_pfn(page), start_pfn);
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check_unmovable_end = min(ALIGN(page_to_pfn(page) + 1, pageblock_nr_pages),
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end_pfn);
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unmovable = has_unmovable_pages(check_unmovable_start, check_unmovable_end,
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migratetype, isol_flags);
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if (!unmovable) {
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unsigned long nr_pages;
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int mt = get_pageblock_migratetype(page);
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set_pageblock_migratetype(page, MIGRATE_ISOLATE);
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zone->nr_isolate_pageblock++;
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nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
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NULL);
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__mod_zone_freepage_state(zone, -nr_pages, mt);
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spin_unlock_irqrestore(&zone->lock, flags);
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return 0;
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}
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spin_unlock_irqrestore(&zone->lock, flags);
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if (isol_flags & REPORT_FAILURE) {
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/*
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* printk() with zone->lock held will likely trigger a
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* lockdep splat, so defer it here.
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*/
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dump_page(unmovable, "unmovable page");
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}
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return -EBUSY;
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}
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static void unset_migratetype_isolate(struct page *page, int migratetype)
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{
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struct zone *zone;
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unsigned long flags, nr_pages;
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bool isolated_page = false;
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unsigned int order;
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struct page *buddy;
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zone = page_zone(page);
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spin_lock_irqsave(&zone->lock, flags);
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if (!is_migrate_isolate_page(page))
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goto out;
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/*
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* Because freepage with more than pageblock_order on isolated
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* pageblock is restricted to merge due to freepage counting problem,
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* it is possible that there is free buddy page.
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* move_freepages_block() doesn't care of merge so we need other
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* approach in order to merge them. Isolation and free will make
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* these pages to be merged.
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*/
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if (PageBuddy(page)) {
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order = buddy_order(page);
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if (order >= pageblock_order && order < MAX_ORDER - 1) {
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buddy = find_buddy_page_pfn(page, page_to_pfn(page),
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order, NULL);
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if (buddy && !is_migrate_isolate_page(buddy)) {
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isolated_page = !!__isolate_free_page(page, order);
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/*
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* Isolating a free page in an isolated pageblock
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* is expected to always work as watermarks don't
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* apply here.
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*/
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VM_WARN_ON(!isolated_page);
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}
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}
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}
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/*
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* If we isolate freepage with more than pageblock_order, there
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* should be no freepage in the range, so we could avoid costly
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* pageblock scanning for freepage moving.
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*
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* We didn't actually touch any of the isolated pages, so place them
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* to the tail of the freelist. This is an optimization for memory
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* onlining - just onlined memory won't immediately be considered for
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* allocation.
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*/
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if (!isolated_page) {
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nr_pages = move_freepages_block(zone, page, migratetype, NULL);
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__mod_zone_freepage_state(zone, nr_pages, migratetype);
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}
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set_pageblock_migratetype(page, migratetype);
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if (isolated_page)
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__putback_isolated_page(page, order, migratetype);
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zone->nr_isolate_pageblock--;
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out:
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spin_unlock_irqrestore(&zone->lock, flags);
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}
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static inline struct page *
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__first_valid_page(unsigned long pfn, unsigned long nr_pages)
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{
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int i;
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for (i = 0; i < nr_pages; i++) {
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struct page *page;
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page = pfn_to_online_page(pfn + i);
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if (!page)
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continue;
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return page;
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}
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return NULL;
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}
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/**
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* isolate_single_pageblock() -- tries to isolate a pageblock that might be
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* within a free or in-use page.
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* @boundary_pfn: pageblock-aligned pfn that a page might cross
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* @flags: isolation flags
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* @gfp_flags: GFP flags used for migrating pages
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* @isolate_before: isolate the pageblock before the boundary_pfn
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* @skip_isolation: the flag to skip the pageblock isolation in second
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* isolate_single_pageblock()
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*
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* Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
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* pageblock. When not all pageblocks within a page are isolated at the same
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* time, free page accounting can go wrong. For example, in the case of
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* MAX_ORDER-1 = pageblock_order + 1, a MAX_ORDER-1 page has two pagelbocks.
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* [ MAX_ORDER-1 ]
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* [ pageblock0 | pageblock1 ]
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* When either pageblock is isolated, if it is a free page, the page is not
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* split into separate migratetype lists, which is supposed to; if it is an
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* in-use page and freed later, __free_one_page() does not split the free page
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* either. The function handles this by splitting the free page or migrating
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* the in-use page then splitting the free page.
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*/
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static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
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gfp_t gfp_flags, bool isolate_before, bool skip_isolation)
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{
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unsigned char saved_mt;
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unsigned long start_pfn;
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unsigned long isolate_pageblock;
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unsigned long pfn;
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struct zone *zone;
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int ret;
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VM_BUG_ON(!IS_ALIGNED(boundary_pfn, pageblock_nr_pages));
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if (isolate_before)
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isolate_pageblock = boundary_pfn - pageblock_nr_pages;
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else
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isolate_pageblock = boundary_pfn;
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/*
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* scan at the beginning of MAX_ORDER_NR_PAGES aligned range to avoid
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* only isolating a subset of pageblocks from a bigger than pageblock
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* free or in-use page. Also make sure all to-be-isolated pageblocks
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* are within the same zone.
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*/
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zone = page_zone(pfn_to_page(isolate_pageblock));
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start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
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zone->zone_start_pfn);
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saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
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if (skip_isolation)
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VM_BUG_ON(!is_migrate_isolate(saved_mt));
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else {
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ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
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isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
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if (ret)
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return ret;
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}
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|
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/*
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* Bail out early when the to-be-isolated pageblock does not form
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* a free or in-use page across boundary_pfn:
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*
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* 1. isolate before boundary_pfn: the page after is not online
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* 2. isolate after boundary_pfn: the page before is not online
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*
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* This also ensures correctness. Without it, when isolate after
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* boundary_pfn and [start_pfn, boundary_pfn) are not online,
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* __first_valid_page() will return unexpected NULL in the for loop
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* below.
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*/
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if (isolate_before) {
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if (!pfn_to_online_page(boundary_pfn))
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return 0;
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} else {
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if (!pfn_to_online_page(boundary_pfn - 1))
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return 0;
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}
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for (pfn = start_pfn; pfn < boundary_pfn;) {
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struct page *page = __first_valid_page(pfn, boundary_pfn - pfn);
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VM_BUG_ON(!page);
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pfn = page_to_pfn(page);
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/*
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* start_pfn is MAX_ORDER_NR_PAGES aligned, if there is any
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* free pages in [start_pfn, boundary_pfn), its head page will
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* always be in the range.
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*/
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if (PageBuddy(page)) {
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int order = buddy_order(page);
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if (pfn + (1UL << order) > boundary_pfn) {
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/* free page changed before split, check it again */
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if (split_free_page(page, order, boundary_pfn - pfn))
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continue;
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}
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pfn += 1UL << order;
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continue;
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}
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/*
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* migrate compound pages then let the free page handling code
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* above do the rest. If migration is not possible, just fail.
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*/
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if (PageCompound(page)) {
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struct page *head = compound_head(page);
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unsigned long head_pfn = page_to_pfn(head);
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unsigned long nr_pages = compound_nr(head);
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|
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if (head_pfn + nr_pages <= boundary_pfn) {
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pfn = head_pfn + nr_pages;
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continue;
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}
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#if defined CONFIG_COMPACTION || defined CONFIG_CMA
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/*
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* hugetlb, lru compound (THP), and movable compound pages
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* can be migrated. Otherwise, fail the isolation.
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*/
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if (PageHuge(page) || PageLRU(page) || __PageMovable(page)) {
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int order;
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unsigned long outer_pfn;
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int page_mt = get_pageblock_migratetype(page);
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bool isolate_page = !is_migrate_isolate_page(page);
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struct compact_control cc = {
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.nr_migratepages = 0,
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.order = -1,
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.zone = page_zone(pfn_to_page(head_pfn)),
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.mode = MIGRATE_SYNC,
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.ignore_skip_hint = true,
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.no_set_skip_hint = true,
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.gfp_mask = gfp_flags,
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.alloc_contig = true,
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};
|
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INIT_LIST_HEAD(&cc.migratepages);
|
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|
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/*
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* XXX: mark the page as MIGRATE_ISOLATE so that
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* no one else can grab the freed page after migration.
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* Ideally, the page should be freed as two separate
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* pages to be added into separate migratetype free
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* lists.
|
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*/
|
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if (isolate_page) {
|
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ret = set_migratetype_isolate(page, page_mt,
|
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flags, head_pfn, head_pfn + nr_pages);
|
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if (ret)
|
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goto failed;
|
|
}
|
|
|
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ret = __alloc_contig_migrate_range(&cc, head_pfn,
|
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head_pfn + nr_pages);
|
|
|
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/*
|
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* restore the page's migratetype so that it can
|
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* be split into separate migratetype free lists
|
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* later.
|
|
*/
|
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if (isolate_page)
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unset_migratetype_isolate(page, page_mt);
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|
|
|
if (ret)
|
|
goto failed;
|
|
/*
|
|
* reset pfn to the head of the free page, so
|
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* that the free page handling code above can split
|
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* the free page to the right migratetype list.
|
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*
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* head_pfn is not used here as a hugetlb page order
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* can be bigger than MAX_ORDER-1, but after it is
|
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* freed, the free page order is not. Use pfn within
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* the range to find the head of the free page.
|
|
*/
|
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order = 0;
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outer_pfn = pfn;
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while (!PageBuddy(pfn_to_page(outer_pfn))) {
|
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/* stop if we cannot find the free page */
|
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if (++order >= MAX_ORDER)
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goto failed;
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outer_pfn &= ~0UL << order;
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}
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pfn = outer_pfn;
|
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continue;
|
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} else
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#endif
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goto failed;
|
|
}
|
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|
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pfn++;
|
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}
|
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return 0;
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|
failed:
|
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/* restore the original migratetype */
|
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if (!skip_isolation)
|
|
unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
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return -EBUSY;
|
|
}
|
|
|
|
/**
|
|
* start_isolate_page_range() - make page-allocation-type of range of pages to
|
|
* be MIGRATE_ISOLATE.
|
|
* @start_pfn: The lower PFN of the range to be isolated.
|
|
* @end_pfn: The upper PFN of the range to be isolated.
|
|
* @migratetype: Migrate type to set in error recovery.
|
|
* @flags: The following flags are allowed (they can be combined in
|
|
* a bit mask)
|
|
* MEMORY_OFFLINE - isolate to offline (!allocate) memory
|
|
* e.g., skip over PageHWPoison() pages
|
|
* and PageOffline() pages.
|
|
* REPORT_FAILURE - report details about the failure to
|
|
* isolate the range
|
|
* @gfp_flags: GFP flags used for migrating pages that sit across the
|
|
* range boundaries.
|
|
*
|
|
* Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
|
|
* the range will never be allocated. Any free pages and pages freed in the
|
|
* future will not be allocated again. If specified range includes migrate types
|
|
* other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
|
|
* pages in the range finally, the caller have to free all pages in the range.
|
|
* test_page_isolated() can be used for test it.
|
|
*
|
|
* The function first tries to isolate the pageblocks at the beginning and end
|
|
* of the range, since there might be pages across the range boundaries.
|
|
* Afterwards, it isolates the rest of the range.
|
|
*
|
|
* There is no high level synchronization mechanism that prevents two threads
|
|
* from trying to isolate overlapping ranges. If this happens, one thread
|
|
* will notice pageblocks in the overlapping range already set to isolate.
|
|
* This happens in set_migratetype_isolate, and set_migratetype_isolate
|
|
* returns an error. We then clean up by restoring the migration type on
|
|
* pageblocks we may have modified and return -EBUSY to caller. This
|
|
* prevents two threads from simultaneously working on overlapping ranges.
|
|
*
|
|
* Please note that there is no strong synchronization with the page allocator
|
|
* either. Pages might be freed while their page blocks are marked ISOLATED.
|
|
* A call to drain_all_pages() after isolation can flush most of them. However
|
|
* in some cases pages might still end up on pcp lists and that would allow
|
|
* for their allocation even when they are in fact isolated already. Depending
|
|
* on how strong of a guarantee the caller needs, zone_pcp_disable/enable()
|
|
* might be used to flush and disable pcplist before isolation and enable after
|
|
* unisolation.
|
|
*
|
|
* Return: 0 on success and -EBUSY if any part of range cannot be isolated.
|
|
*/
|
|
int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
|
|
int migratetype, int flags, gfp_t gfp_flags)
|
|
{
|
|
unsigned long pfn;
|
|
struct page *page;
|
|
/* isolation is done at page block granularity */
|
|
unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
|
|
unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
|
|
int ret;
|
|
bool skip_isolation = false;
|
|
|
|
/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
|
|
ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, skip_isolation);
|
|
if (ret)
|
|
return ret;
|
|
|
|
if (isolate_start == isolate_end - pageblock_nr_pages)
|
|
skip_isolation = true;
|
|
|
|
/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
|
|
ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation);
|
|
if (ret) {
|
|
unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
|
|
return ret;
|
|
}
|
|
|
|
/* skip isolated pageblocks at the beginning and end */
|
|
for (pfn = isolate_start + pageblock_nr_pages;
|
|
pfn < isolate_end - pageblock_nr_pages;
|
|
pfn += pageblock_nr_pages) {
|
|
page = __first_valid_page(pfn, pageblock_nr_pages);
|
|
if (page && set_migratetype_isolate(page, migratetype, flags,
|
|
start_pfn, end_pfn)) {
|
|
undo_isolate_page_range(isolate_start, pfn, migratetype);
|
|
unset_migratetype_isolate(
|
|
pfn_to_page(isolate_end - pageblock_nr_pages),
|
|
migratetype);
|
|
return -EBUSY;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Make isolated pages available again.
|
|
*/
|
|
void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
|
|
int migratetype)
|
|
{
|
|
unsigned long pfn;
|
|
struct page *page;
|
|
unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
|
|
unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
|
|
|
|
|
|
for (pfn = isolate_start;
|
|
pfn < isolate_end;
|
|
pfn += pageblock_nr_pages) {
|
|
page = __first_valid_page(pfn, pageblock_nr_pages);
|
|
if (!page || !is_migrate_isolate_page(page))
|
|
continue;
|
|
unset_migratetype_isolate(page, migratetype);
|
|
}
|
|
}
|
|
/*
|
|
* Test all pages in the range is free(means isolated) or not.
|
|
* all pages in [start_pfn...end_pfn) must be in the same zone.
|
|
* zone->lock must be held before call this.
|
|
*
|
|
* Returns the last tested pfn.
|
|
*/
|
|
static unsigned long
|
|
__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
|
|
int flags)
|
|
{
|
|
struct page *page;
|
|
|
|
while (pfn < end_pfn) {
|
|
page = pfn_to_page(pfn);
|
|
if (PageBuddy(page))
|
|
/*
|
|
* If the page is on a free list, it has to be on
|
|
* the correct MIGRATE_ISOLATE freelist. There is no
|
|
* simple way to verify that as VM_BUG_ON(), though.
|
|
*/
|
|
pfn += 1 << buddy_order(page);
|
|
else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
|
|
/* A HWPoisoned page cannot be also PageBuddy */
|
|
pfn++;
|
|
else if ((flags & MEMORY_OFFLINE) && PageOffline(page) &&
|
|
!page_count(page))
|
|
/*
|
|
* The responsible driver agreed to skip PageOffline()
|
|
* pages when offlining memory by dropping its
|
|
* reference in MEM_GOING_OFFLINE.
|
|
*/
|
|
pfn++;
|
|
else
|
|
break;
|
|
}
|
|
|
|
return pfn;
|
|
}
|
|
|
|
/* Caller should ensure that requested range is in a single zone */
|
|
int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
|
|
int isol_flags)
|
|
{
|
|
unsigned long pfn, flags;
|
|
struct page *page;
|
|
struct zone *zone;
|
|
int ret;
|
|
|
|
/*
|
|
* Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
|
|
* are not aligned to pageblock_nr_pages.
|
|
* Then we just check migratetype first.
|
|
*/
|
|
for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
|
|
page = __first_valid_page(pfn, pageblock_nr_pages);
|
|
if (page && !is_migrate_isolate_page(page))
|
|
break;
|
|
}
|
|
page = __first_valid_page(start_pfn, end_pfn - start_pfn);
|
|
if ((pfn < end_pfn) || !page) {
|
|
ret = -EBUSY;
|
|
goto out;
|
|
}
|
|
|
|
/* Check all pages are free or marked as ISOLATED */
|
|
zone = page_zone(page);
|
|
spin_lock_irqsave(&zone->lock, flags);
|
|
pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags);
|
|
spin_unlock_irqrestore(&zone->lock, flags);
|
|
|
|
ret = pfn < end_pfn ? -EBUSY : 0;
|
|
|
|
out:
|
|
trace_test_pages_isolated(start_pfn, end_pfn, pfn);
|
|
|
|
return ret;
|
|
}
|