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![David Hildenbrand](/assets/img/avatar_default.png)
We have two types of users of page isolation: 1. Memory offlining: Offline memory so it can be unplugged. Memory won't be touched. 2. Memory allocation: Allocate memory (e.g., alloc_contig_range()) to become the owner of the memory and make use of it. For example, in case we want to offline memory, we can ignore (skip over) PageHWPoison() pages, as the memory won't get used. We can allow to offline memory. In contrast, we don't want to allow to allocate such memory. Let's generalize the approach so we can special case other types of pages we want to skip over in case we offline memory. While at it, also pass the same flags to test_pages_isolated(). Link: http://lkml.kernel.org/r/20191021172353.3056-3-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Suggested-by: Michal Hocko <mhocko@suse.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: David Hildenbrand <david@redhat.com> Cc: Pingfan Liu <kernelfans@gmail.com> Cc: Qian Cai <cai@lca.pw> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Pavel Tatashin <pavel.tatashin@microsoft.com> Cc: Wei Yang <richard.weiyang@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
323 lines
9.2 KiB
C
323 lines
9.2 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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static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
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{
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struct zone *zone;
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unsigned long flags, pfn;
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struct memory_isolate_notify arg;
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int notifier_ret;
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int ret = -EBUSY;
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zone = page_zone(page);
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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. Return -EBUSY
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*/
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if (is_migrate_isolate_page(page))
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goto out;
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pfn = page_to_pfn(page);
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arg.start_pfn = pfn;
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arg.nr_pages = pageblock_nr_pages;
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arg.pages_found = 0;
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/*
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* It may be possible to isolate a pageblock even if the
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* migratetype is not MIGRATE_MOVABLE. The memory isolation
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* notifier chain is used by balloon drivers to return the
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* number of pages in a range that are held by the balloon
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* driver to shrink memory. If all the pages are accounted for
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* by balloons, are free, or on the LRU, isolation can continue.
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* Later, for example, when memory hotplug notifier runs, these
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* pages reported as "can be isolated" should be isolated(freed)
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* by the balloon driver through the memory notifier chain.
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*/
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notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
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notifier_ret = notifier_to_errno(notifier_ret);
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if (notifier_ret)
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goto out;
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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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if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype,
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isol_flags))
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ret = 0;
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/*
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* immobile means "not-on-lru" pages. If immobile is larger than
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* removable-by-driver pages reported by notifier, we'll fail.
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*/
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out:
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if (!ret) {
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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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}
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spin_unlock_irqrestore(&zone->lock, flags);
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if (!ret)
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drain_all_pages(zone);
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return ret;
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}
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static void unset_migratetype_isolate(struct page *page, unsigned 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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unsigned long pfn, buddy_pfn;
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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 = page_order(page);
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if (order >= pageblock_order) {
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pfn = page_to_pfn(page);
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buddy_pfn = __find_buddy_pfn(pfn, order);
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buddy = page + (buddy_pfn - pfn);
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if (pfn_valid_within(buddy_pfn) &&
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!is_migrate_isolate_page(buddy)) {
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__isolate_free_page(page, order);
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isolated_page = true;
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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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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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zone->nr_isolate_pageblock--;
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out:
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spin_unlock_irqrestore(&zone->lock, flags);
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if (isolated_page) {
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post_alloc_hook(page, order, __GFP_MOVABLE);
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__free_pages(page, order);
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}
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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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* start_isolate_page_range() - make page-allocation-type of range of pages to
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* be MIGRATE_ISOLATE.
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* @start_pfn: The lower PFN of the range to be isolated.
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* @end_pfn: The upper PFN of the range to be isolated.
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* start_pfn/end_pfn must be aligned to pageblock_order.
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* @migratetype: Migrate type to set in error recovery.
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* @flags: The following flags are allowed (they can be combined in
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* a bit mask)
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* MEMORY_OFFLINE - isolate to offline (!allocate) memory
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* e.g., skip over PageHWPoison() pages
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* REPORT_FAILURE - report details about the failure to
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* isolate the range
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*
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* Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
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* the range will never be allocated. Any free pages and pages freed in the
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* future will not be allocated again. If specified range includes migrate types
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* other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all
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* pages in the range finally, the caller have to free all pages in the range.
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* test_page_isolated() can be used for test it.
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*
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* There is no high level synchronization mechanism that prevents two threads
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* from trying to isolate overlapping ranges. If this happens, one thread
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* will notice pageblocks in the overlapping range already set to isolate.
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* This happens in set_migratetype_isolate, and set_migratetype_isolate
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* returns an error. We then clean up by restoring the migration type on
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* pageblocks we may have modified and return -EBUSY to caller. This
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* prevents two threads from simultaneously working on overlapping ranges.
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*
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* Return: the number of isolated pageblocks on success and -EBUSY if any part
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* of range cannot be isolated.
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*/
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int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
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unsigned migratetype, int flags)
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{
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unsigned long pfn;
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unsigned long undo_pfn;
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struct page *page;
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int nr_isolate_pageblock = 0;
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BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
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BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
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for (pfn = start_pfn;
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pfn < end_pfn;
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pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (page) {
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if (set_migratetype_isolate(page, migratetype, flags)) {
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undo_pfn = pfn;
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goto undo;
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}
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nr_isolate_pageblock++;
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}
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}
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return nr_isolate_pageblock;
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undo:
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for (pfn = start_pfn;
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pfn < undo_pfn;
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pfn += pageblock_nr_pages) {
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struct page *page = pfn_to_online_page(pfn);
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if (!page)
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continue;
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unset_migratetype_isolate(page, migratetype);
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}
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return -EBUSY;
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}
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/*
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* Make isolated pages available again.
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*/
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void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
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unsigned migratetype)
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{
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unsigned long pfn;
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struct page *page;
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BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
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BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
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for (pfn = start_pfn;
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pfn < end_pfn;
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pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (!page || !is_migrate_isolate_page(page))
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continue;
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unset_migratetype_isolate(page, migratetype);
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}
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}
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/*
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* Test all pages in the range is free(means isolated) or not.
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* all pages in [start_pfn...end_pfn) must be in the same zone.
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* zone->lock must be held before call this.
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*
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* Returns the last tested pfn.
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*/
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static unsigned long
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__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
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int flags)
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{
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struct page *page;
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while (pfn < end_pfn) {
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if (!pfn_valid_within(pfn)) {
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pfn++;
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continue;
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}
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page = pfn_to_page(pfn);
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if (PageBuddy(page))
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/*
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* If the page is on a free list, it has to be on
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* the correct MIGRATE_ISOLATE freelist. There is no
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* simple way to verify that as VM_BUG_ON(), though.
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*/
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pfn += 1 << page_order(page);
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else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page))
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/* A HWPoisoned page cannot be also PageBuddy */
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pfn++;
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else
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break;
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}
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return pfn;
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}
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/* Caller should ensure that requested range is in a single zone */
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int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
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int isol_flags)
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{
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unsigned long pfn, flags;
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struct page *page;
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struct zone *zone;
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/*
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* Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
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* are not aligned to pageblock_nr_pages.
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* Then we just check migratetype first.
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*/
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for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
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page = __first_valid_page(pfn, pageblock_nr_pages);
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if (page && !is_migrate_isolate_page(page))
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break;
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}
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page = __first_valid_page(start_pfn, end_pfn - start_pfn);
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if ((pfn < end_pfn) || !page)
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return -EBUSY;
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/* Check all pages are free or marked as ISOLATED */
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zone = page_zone(page);
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spin_lock_irqsave(&zone->lock, flags);
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pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, isol_flags);
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spin_unlock_irqrestore(&zone->lock, flags);
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trace_test_pages_isolated(start_pfn, end_pfn, pfn);
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return pfn < end_pfn ? -EBUSY : 0;
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}
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struct page *alloc_migrate_target(struct page *page, unsigned long private)
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{
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return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
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}
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