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![Srivatsa S. Bhat](/assets/img/avatar_default.png)
The comment over migrate_pages() looks quite weird, and makes it hard to grasp what it is trying to say. Rewrite it more comprehensibly. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1758 lines
44 KiB
C
1758 lines
44 KiB
C
/*
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* Memory Migration functionality - linux/mm/migration.c
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*
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* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
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*
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* Page migration was first developed in the context of the memory hotplug
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* project. The main authors of the migration code are:
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*
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* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
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* Hirokazu Takahashi <taka@valinux.co.jp>
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* Dave Hansen <haveblue@us.ibm.com>
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* Christoph Lameter
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*/
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#include <linux/migrate.h>
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#include <linux/export.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/pagemap.h>
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#include <linux/buffer_head.h>
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#include <linux/mm_inline.h>
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#include <linux/nsproxy.h>
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#include <linux/pagevec.h>
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#include <linux/ksm.h>
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#include <linux/rmap.h>
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#include <linux/topology.h>
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/writeback.h>
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#include <linux/mempolicy.h>
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#include <linux/vmalloc.h>
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#include <linux/security.h>
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#include <linux/memcontrol.h>
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#include <linux/syscalls.h>
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#include <linux/hugetlb.h>
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#include <linux/hugetlb_cgroup.h>
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#include <linux/gfp.h>
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#include <linux/balloon_compaction.h>
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#include <asm/tlbflush.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/migrate.h>
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#include "internal.h"
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/*
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* migrate_prep() needs to be called before we start compiling a list of pages
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* to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
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* undesirable, use migrate_prep_local()
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*/
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int migrate_prep(void)
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{
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/*
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* Clear the LRU lists so pages can be isolated.
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* Note that pages may be moved off the LRU after we have
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* drained them. Those pages will fail to migrate like other
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* pages that may be busy.
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*/
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lru_add_drain_all();
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return 0;
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}
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/* Do the necessary work of migrate_prep but not if it involves other CPUs */
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int migrate_prep_local(void)
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{
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lru_add_drain();
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return 0;
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}
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/*
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* Add isolated pages on the list back to the LRU under page lock
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* to avoid leaking evictable pages back onto unevictable list.
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*/
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void putback_lru_pages(struct list_head *l)
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{
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struct page *page;
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struct page *page2;
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list_for_each_entry_safe(page, page2, l, lru) {
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list_del(&page->lru);
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dec_zone_page_state(page, NR_ISOLATED_ANON +
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page_is_file_cache(page));
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putback_lru_page(page);
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}
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}
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/*
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* Put previously isolated pages back onto the appropriate lists
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* from where they were once taken off for compaction/migration.
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*
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* This function shall be used instead of putback_lru_pages(),
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* whenever the isolated pageset has been built by isolate_migratepages_range()
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*/
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void putback_movable_pages(struct list_head *l)
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{
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struct page *page;
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struct page *page2;
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list_for_each_entry_safe(page, page2, l, lru) {
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list_del(&page->lru);
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dec_zone_page_state(page, NR_ISOLATED_ANON +
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page_is_file_cache(page));
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if (unlikely(balloon_page_movable(page)))
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balloon_page_putback(page);
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else
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putback_lru_page(page);
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}
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}
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/*
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* Restore a potential migration pte to a working pte entry
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*/
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static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
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unsigned long addr, void *old)
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{
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struct mm_struct *mm = vma->vm_mm;
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swp_entry_t entry;
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pmd_t *pmd;
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pte_t *ptep, pte;
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spinlock_t *ptl;
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if (unlikely(PageHuge(new))) {
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ptep = huge_pte_offset(mm, addr);
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if (!ptep)
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goto out;
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ptl = &mm->page_table_lock;
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} else {
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pmd = mm_find_pmd(mm, addr);
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if (!pmd)
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goto out;
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if (pmd_trans_huge(*pmd))
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goto out;
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ptep = pte_offset_map(pmd, addr);
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/*
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* Peek to check is_swap_pte() before taking ptlock? No, we
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* can race mremap's move_ptes(), which skips anon_vma lock.
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*/
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ptl = pte_lockptr(mm, pmd);
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}
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spin_lock(ptl);
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pte = *ptep;
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if (!is_swap_pte(pte))
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goto unlock;
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entry = pte_to_swp_entry(pte);
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if (!is_migration_entry(entry) ||
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migration_entry_to_page(entry) != old)
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goto unlock;
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get_page(new);
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pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
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if (is_write_migration_entry(entry))
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pte = pte_mkwrite(pte);
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#ifdef CONFIG_HUGETLB_PAGE
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if (PageHuge(new)) {
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pte = pte_mkhuge(pte);
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pte = arch_make_huge_pte(pte, vma, new, 0);
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}
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#endif
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flush_cache_page(vma, addr, pte_pfn(pte));
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set_pte_at(mm, addr, ptep, pte);
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if (PageHuge(new)) {
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if (PageAnon(new))
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hugepage_add_anon_rmap(new, vma, addr);
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else
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page_dup_rmap(new);
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} else if (PageAnon(new))
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page_add_anon_rmap(new, vma, addr);
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else
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page_add_file_rmap(new);
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/* No need to invalidate - it was non-present before */
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update_mmu_cache(vma, addr, ptep);
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unlock:
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pte_unmap_unlock(ptep, ptl);
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out:
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return SWAP_AGAIN;
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}
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/*
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* Get rid of all migration entries and replace them by
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* references to the indicated page.
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*/
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static void remove_migration_ptes(struct page *old, struct page *new)
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{
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rmap_walk(new, remove_migration_pte, old);
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}
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/*
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* Something used the pte of a page under migration. We need to
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* get to the page and wait until migration is finished.
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* When we return from this function the fault will be retried.
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*/
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void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address)
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{
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pte_t *ptep, pte;
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spinlock_t *ptl;
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swp_entry_t entry;
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struct page *page;
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ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
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pte = *ptep;
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if (!is_swap_pte(pte))
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goto out;
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entry = pte_to_swp_entry(pte);
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if (!is_migration_entry(entry))
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goto out;
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page = migration_entry_to_page(entry);
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/*
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* Once radix-tree replacement of page migration started, page_count
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* *must* be zero. And, we don't want to call wait_on_page_locked()
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* against a page without get_page().
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* So, we use get_page_unless_zero(), here. Even failed, page fault
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* will occur again.
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*/
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if (!get_page_unless_zero(page))
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goto out;
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pte_unmap_unlock(ptep, ptl);
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wait_on_page_locked(page);
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put_page(page);
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return;
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out:
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pte_unmap_unlock(ptep, ptl);
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}
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#ifdef CONFIG_BLOCK
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/* Returns true if all buffers are successfully locked */
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static bool buffer_migrate_lock_buffers(struct buffer_head *head,
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enum migrate_mode mode)
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{
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struct buffer_head *bh = head;
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/* Simple case, sync compaction */
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if (mode != MIGRATE_ASYNC) {
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do {
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get_bh(bh);
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lock_buffer(bh);
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bh = bh->b_this_page;
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} while (bh != head);
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return true;
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}
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/* async case, we cannot block on lock_buffer so use trylock_buffer */
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do {
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get_bh(bh);
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if (!trylock_buffer(bh)) {
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/*
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* We failed to lock the buffer and cannot stall in
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* async migration. Release the taken locks
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*/
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struct buffer_head *failed_bh = bh;
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put_bh(failed_bh);
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bh = head;
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while (bh != failed_bh) {
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unlock_buffer(bh);
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put_bh(bh);
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bh = bh->b_this_page;
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}
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return false;
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}
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bh = bh->b_this_page;
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} while (bh != head);
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return true;
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}
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#else
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static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
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enum migrate_mode mode)
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{
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return true;
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}
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#endif /* CONFIG_BLOCK */
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/*
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* Replace the page in the mapping.
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*
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* The number of remaining references must be:
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* 1 for anonymous pages without a mapping
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* 2 for pages with a mapping
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* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
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*/
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static int migrate_page_move_mapping(struct address_space *mapping,
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struct page *newpage, struct page *page,
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struct buffer_head *head, enum migrate_mode mode)
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{
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int expected_count = 0;
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void **pslot;
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if (!mapping) {
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/* Anonymous page without mapping */
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if (page_count(page) != 1)
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return -EAGAIN;
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return MIGRATEPAGE_SUCCESS;
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}
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spin_lock_irq(&mapping->tree_lock);
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pslot = radix_tree_lookup_slot(&mapping->page_tree,
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page_index(page));
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expected_count = 2 + page_has_private(page);
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if (page_count(page) != expected_count ||
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radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
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spin_unlock_irq(&mapping->tree_lock);
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return -EAGAIN;
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}
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if (!page_freeze_refs(page, expected_count)) {
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spin_unlock_irq(&mapping->tree_lock);
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return -EAGAIN;
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}
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/*
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* In the async migration case of moving a page with buffers, lock the
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* buffers using trylock before the mapping is moved. If the mapping
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* was moved, we later failed to lock the buffers and could not move
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* the mapping back due to an elevated page count, we would have to
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* block waiting on other references to be dropped.
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*/
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if (mode == MIGRATE_ASYNC && head &&
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!buffer_migrate_lock_buffers(head, mode)) {
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page_unfreeze_refs(page, expected_count);
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spin_unlock_irq(&mapping->tree_lock);
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return -EAGAIN;
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}
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/*
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* Now we know that no one else is looking at the page.
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*/
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get_page(newpage); /* add cache reference */
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if (PageSwapCache(page)) {
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SetPageSwapCache(newpage);
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set_page_private(newpage, page_private(page));
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}
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radix_tree_replace_slot(pslot, newpage);
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/*
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* Drop cache reference from old page by unfreezing
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* to one less reference.
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* We know this isn't the last reference.
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*/
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page_unfreeze_refs(page, expected_count - 1);
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/*
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* If moved to a different zone then also account
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* the page for that zone. Other VM counters will be
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* taken care of when we establish references to the
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* new page and drop references to the old page.
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*
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* Note that anonymous pages are accounted for
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* via NR_FILE_PAGES and NR_ANON_PAGES if they
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* are mapped to swap space.
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*/
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__dec_zone_page_state(page, NR_FILE_PAGES);
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__inc_zone_page_state(newpage, NR_FILE_PAGES);
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if (!PageSwapCache(page) && PageSwapBacked(page)) {
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__dec_zone_page_state(page, NR_SHMEM);
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__inc_zone_page_state(newpage, NR_SHMEM);
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}
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spin_unlock_irq(&mapping->tree_lock);
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return MIGRATEPAGE_SUCCESS;
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}
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/*
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* The expected number of remaining references is the same as that
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* of migrate_page_move_mapping().
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*/
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int migrate_huge_page_move_mapping(struct address_space *mapping,
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struct page *newpage, struct page *page)
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{
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int expected_count;
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void **pslot;
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if (!mapping) {
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if (page_count(page) != 1)
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return -EAGAIN;
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return MIGRATEPAGE_SUCCESS;
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}
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spin_lock_irq(&mapping->tree_lock);
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pslot = radix_tree_lookup_slot(&mapping->page_tree,
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page_index(page));
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expected_count = 2 + page_has_private(page);
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if (page_count(page) != expected_count ||
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radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
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spin_unlock_irq(&mapping->tree_lock);
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return -EAGAIN;
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}
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if (!page_freeze_refs(page, expected_count)) {
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spin_unlock_irq(&mapping->tree_lock);
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return -EAGAIN;
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}
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get_page(newpage);
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radix_tree_replace_slot(pslot, newpage);
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page_unfreeze_refs(page, expected_count - 1);
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spin_unlock_irq(&mapping->tree_lock);
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return MIGRATEPAGE_SUCCESS;
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}
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/*
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* Copy the page to its new location
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*/
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void migrate_page_copy(struct page *newpage, struct page *page)
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{
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if (PageHuge(page) || PageTransHuge(page))
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copy_huge_page(newpage, page);
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else
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copy_highpage(newpage, page);
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if (PageError(page))
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SetPageError(newpage);
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if (PageReferenced(page))
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SetPageReferenced(newpage);
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if (PageUptodate(page))
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SetPageUptodate(newpage);
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if (TestClearPageActive(page)) {
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VM_BUG_ON(PageUnevictable(page));
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SetPageActive(newpage);
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} else if (TestClearPageUnevictable(page))
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SetPageUnevictable(newpage);
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if (PageChecked(page))
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SetPageChecked(newpage);
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if (PageMappedToDisk(page))
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SetPageMappedToDisk(newpage);
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|
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if (PageDirty(page)) {
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clear_page_dirty_for_io(page);
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/*
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* Want to mark the page and the radix tree as dirty, and
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* redo the accounting that clear_page_dirty_for_io undid,
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* but we can't use set_page_dirty because that function
|
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* is actually a signal that all of the page has become dirty.
|
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* Whereas only part of our page may be dirty.
|
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*/
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if (PageSwapBacked(page))
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SetPageDirty(newpage);
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else
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__set_page_dirty_nobuffers(newpage);
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}
|
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|
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mlock_migrate_page(newpage, page);
|
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ksm_migrate_page(newpage, page);
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/*
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* Please do not reorder this without considering how mm/ksm.c's
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* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
|
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*/
|
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ClearPageSwapCache(page);
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ClearPagePrivate(page);
|
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set_page_private(page, 0);
|
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|
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/*
|
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* If any waiters have accumulated on the new page then
|
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* wake them up.
|
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*/
|
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if (PageWriteback(newpage))
|
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end_page_writeback(newpage);
|
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}
|
|
|
|
/************************************************************
|
|
* Migration functions
|
|
***********************************************************/
|
|
|
|
/* Always fail migration. Used for mappings that are not movable */
|
|
int fail_migrate_page(struct address_space *mapping,
|
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struct page *newpage, struct page *page)
|
|
{
|
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return -EIO;
|
|
}
|
|
EXPORT_SYMBOL(fail_migrate_page);
|
|
|
|
/*
|
|
* Common logic to directly migrate a single page suitable for
|
|
* pages that do not use PagePrivate/PagePrivate2.
|
|
*
|
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* Pages are locked upon entry and exit.
|
|
*/
|
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int migrate_page(struct address_space *mapping,
|
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struct page *newpage, struct page *page,
|
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enum migrate_mode mode)
|
|
{
|
|
int rc;
|
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|
|
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
|
|
|
|
rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
|
|
|
|
if (rc != MIGRATEPAGE_SUCCESS)
|
|
return rc;
|
|
|
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migrate_page_copy(newpage, page);
|
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return MIGRATEPAGE_SUCCESS;
|
|
}
|
|
EXPORT_SYMBOL(migrate_page);
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
/*
|
|
* Migration function for pages with buffers. This function can only be used
|
|
* if the underlying filesystem guarantees that no other references to "page"
|
|
* exist.
|
|
*/
|
|
int buffer_migrate_page(struct address_space *mapping,
|
|
struct page *newpage, struct page *page, enum migrate_mode mode)
|
|
{
|
|
struct buffer_head *bh, *head;
|
|
int rc;
|
|
|
|
if (!page_has_buffers(page))
|
|
return migrate_page(mapping, newpage, page, mode);
|
|
|
|
head = page_buffers(page);
|
|
|
|
rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
|
|
|
|
if (rc != MIGRATEPAGE_SUCCESS)
|
|
return rc;
|
|
|
|
/*
|
|
* In the async case, migrate_page_move_mapping locked the buffers
|
|
* with an IRQ-safe spinlock held. In the sync case, the buffers
|
|
* need to be locked now
|
|
*/
|
|
if (mode != MIGRATE_ASYNC)
|
|
BUG_ON(!buffer_migrate_lock_buffers(head, mode));
|
|
|
|
ClearPagePrivate(page);
|
|
set_page_private(newpage, page_private(page));
|
|
set_page_private(page, 0);
|
|
put_page(page);
|
|
get_page(newpage);
|
|
|
|
bh = head;
|
|
do {
|
|
set_bh_page(bh, newpage, bh_offset(bh));
|
|
bh = bh->b_this_page;
|
|
|
|
} while (bh != head);
|
|
|
|
SetPagePrivate(newpage);
|
|
|
|
migrate_page_copy(newpage, page);
|
|
|
|
bh = head;
|
|
do {
|
|
unlock_buffer(bh);
|
|
put_bh(bh);
|
|
bh = bh->b_this_page;
|
|
|
|
} while (bh != head);
|
|
|
|
return MIGRATEPAGE_SUCCESS;
|
|
}
|
|
EXPORT_SYMBOL(buffer_migrate_page);
|
|
#endif
|
|
|
|
/*
|
|
* Writeback a page to clean the dirty state
|
|
*/
|
|
static int writeout(struct address_space *mapping, struct page *page)
|
|
{
|
|
struct writeback_control wbc = {
|
|
.sync_mode = WB_SYNC_NONE,
|
|
.nr_to_write = 1,
|
|
.range_start = 0,
|
|
.range_end = LLONG_MAX,
|
|
.for_reclaim = 1
|
|
};
|
|
int rc;
|
|
|
|
if (!mapping->a_ops->writepage)
|
|
/* No write method for the address space */
|
|
return -EINVAL;
|
|
|
|
if (!clear_page_dirty_for_io(page))
|
|
/* Someone else already triggered a write */
|
|
return -EAGAIN;
|
|
|
|
/*
|
|
* A dirty page may imply that the underlying filesystem has
|
|
* the page on some queue. So the page must be clean for
|
|
* migration. Writeout may mean we loose the lock and the
|
|
* page state is no longer what we checked for earlier.
|
|
* At this point we know that the migration attempt cannot
|
|
* be successful.
|
|
*/
|
|
remove_migration_ptes(page, page);
|
|
|
|
rc = mapping->a_ops->writepage(page, &wbc);
|
|
|
|
if (rc != AOP_WRITEPAGE_ACTIVATE)
|
|
/* unlocked. Relock */
|
|
lock_page(page);
|
|
|
|
return (rc < 0) ? -EIO : -EAGAIN;
|
|
}
|
|
|
|
/*
|
|
* Default handling if a filesystem does not provide a migration function.
|
|
*/
|
|
static int fallback_migrate_page(struct address_space *mapping,
|
|
struct page *newpage, struct page *page, enum migrate_mode mode)
|
|
{
|
|
if (PageDirty(page)) {
|
|
/* Only writeback pages in full synchronous migration */
|
|
if (mode != MIGRATE_SYNC)
|
|
return -EBUSY;
|
|
return writeout(mapping, page);
|
|
}
|
|
|
|
/*
|
|
* Buffers may be managed in a filesystem specific way.
|
|
* We must have no buffers or drop them.
|
|
*/
|
|
if (page_has_private(page) &&
|
|
!try_to_release_page(page, GFP_KERNEL))
|
|
return -EAGAIN;
|
|
|
|
return migrate_page(mapping, newpage, page, mode);
|
|
}
|
|
|
|
/*
|
|
* Move a page to a newly allocated page
|
|
* The page is locked and all ptes have been successfully removed.
|
|
*
|
|
* The new page will have replaced the old page if this function
|
|
* is successful.
|
|
*
|
|
* Return value:
|
|
* < 0 - error code
|
|
* MIGRATEPAGE_SUCCESS - success
|
|
*/
|
|
static int move_to_new_page(struct page *newpage, struct page *page,
|
|
int remap_swapcache, enum migrate_mode mode)
|
|
{
|
|
struct address_space *mapping;
|
|
int rc;
|
|
|
|
/*
|
|
* Block others from accessing the page when we get around to
|
|
* establishing additional references. We are the only one
|
|
* holding a reference to the new page at this point.
|
|
*/
|
|
if (!trylock_page(newpage))
|
|
BUG();
|
|
|
|
/* Prepare mapping for the new page.*/
|
|
newpage->index = page->index;
|
|
newpage->mapping = page->mapping;
|
|
if (PageSwapBacked(page))
|
|
SetPageSwapBacked(newpage);
|
|
|
|
mapping = page_mapping(page);
|
|
if (!mapping)
|
|
rc = migrate_page(mapping, newpage, page, mode);
|
|
else if (mapping->a_ops->migratepage)
|
|
/*
|
|
* Most pages have a mapping and most filesystems provide a
|
|
* migratepage callback. Anonymous pages are part of swap
|
|
* space which also has its own migratepage callback. This
|
|
* is the most common path for page migration.
|
|
*/
|
|
rc = mapping->a_ops->migratepage(mapping,
|
|
newpage, page, mode);
|
|
else
|
|
rc = fallback_migrate_page(mapping, newpage, page, mode);
|
|
|
|
if (rc != MIGRATEPAGE_SUCCESS) {
|
|
newpage->mapping = NULL;
|
|
} else {
|
|
if (remap_swapcache)
|
|
remove_migration_ptes(page, newpage);
|
|
page->mapping = NULL;
|
|
}
|
|
|
|
unlock_page(newpage);
|
|
|
|
return rc;
|
|
}
|
|
|
|
static int __unmap_and_move(struct page *page, struct page *newpage,
|
|
int force, enum migrate_mode mode)
|
|
{
|
|
int rc = -EAGAIN;
|
|
int remap_swapcache = 1;
|
|
struct mem_cgroup *mem;
|
|
struct anon_vma *anon_vma = NULL;
|
|
|
|
if (!trylock_page(page)) {
|
|
if (!force || mode == MIGRATE_ASYNC)
|
|
goto out;
|
|
|
|
/*
|
|
* It's not safe for direct compaction to call lock_page.
|
|
* For example, during page readahead pages are added locked
|
|
* to the LRU. Later, when the IO completes the pages are
|
|
* marked uptodate and unlocked. However, the queueing
|
|
* could be merging multiple pages for one bio (e.g.
|
|
* mpage_readpages). If an allocation happens for the
|
|
* second or third page, the process can end up locking
|
|
* the same page twice and deadlocking. Rather than
|
|
* trying to be clever about what pages can be locked,
|
|
* avoid the use of lock_page for direct compaction
|
|
* altogether.
|
|
*/
|
|
if (current->flags & PF_MEMALLOC)
|
|
goto out;
|
|
|
|
lock_page(page);
|
|
}
|
|
|
|
/* charge against new page */
|
|
mem_cgroup_prepare_migration(page, newpage, &mem);
|
|
|
|
if (PageWriteback(page)) {
|
|
/*
|
|
* Only in the case of a full synchronous migration is it
|
|
* necessary to wait for PageWriteback. In the async case,
|
|
* the retry loop is too short and in the sync-light case,
|
|
* the overhead of stalling is too much
|
|
*/
|
|
if (mode != MIGRATE_SYNC) {
|
|
rc = -EBUSY;
|
|
goto uncharge;
|
|
}
|
|
if (!force)
|
|
goto uncharge;
|
|
wait_on_page_writeback(page);
|
|
}
|
|
/*
|
|
* By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
|
|
* we cannot notice that anon_vma is freed while we migrates a page.
|
|
* This get_anon_vma() delays freeing anon_vma pointer until the end
|
|
* of migration. File cache pages are no problem because of page_lock()
|
|
* File Caches may use write_page() or lock_page() in migration, then,
|
|
* just care Anon page here.
|
|
*/
|
|
if (PageAnon(page) && !PageKsm(page)) {
|
|
/*
|
|
* Only page_lock_anon_vma_read() understands the subtleties of
|
|
* getting a hold on an anon_vma from outside one of its mms.
|
|
*/
|
|
anon_vma = page_get_anon_vma(page);
|
|
if (anon_vma) {
|
|
/*
|
|
* Anon page
|
|
*/
|
|
} else if (PageSwapCache(page)) {
|
|
/*
|
|
* We cannot be sure that the anon_vma of an unmapped
|
|
* swapcache page is safe to use because we don't
|
|
* know in advance if the VMA that this page belonged
|
|
* to still exists. If the VMA and others sharing the
|
|
* data have been freed, then the anon_vma could
|
|
* already be invalid.
|
|
*
|
|
* To avoid this possibility, swapcache pages get
|
|
* migrated but are not remapped when migration
|
|
* completes
|
|
*/
|
|
remap_swapcache = 0;
|
|
} else {
|
|
goto uncharge;
|
|
}
|
|
}
|
|
|
|
if (unlikely(balloon_page_movable(page))) {
|
|
/*
|
|
* A ballooned page does not need any special attention from
|
|
* physical to virtual reverse mapping procedures.
|
|
* Skip any attempt to unmap PTEs or to remap swap cache,
|
|
* in order to avoid burning cycles at rmap level, and perform
|
|
* the page migration right away (proteced by page lock).
|
|
*/
|
|
rc = balloon_page_migrate(newpage, page, mode);
|
|
goto uncharge;
|
|
}
|
|
|
|
/*
|
|
* Corner case handling:
|
|
* 1. When a new swap-cache page is read into, it is added to the LRU
|
|
* and treated as swapcache but it has no rmap yet.
|
|
* Calling try_to_unmap() against a page->mapping==NULL page will
|
|
* trigger a BUG. So handle it here.
|
|
* 2. An orphaned page (see truncate_complete_page) might have
|
|
* fs-private metadata. The page can be picked up due to memory
|
|
* offlining. Everywhere else except page reclaim, the page is
|
|
* invisible to the vm, so the page can not be migrated. So try to
|
|
* free the metadata, so the page can be freed.
|
|
*/
|
|
if (!page->mapping) {
|
|
VM_BUG_ON(PageAnon(page));
|
|
if (page_has_private(page)) {
|
|
try_to_free_buffers(page);
|
|
goto uncharge;
|
|
}
|
|
goto skip_unmap;
|
|
}
|
|
|
|
/* Establish migration ptes or remove ptes */
|
|
try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
|
|
|
|
skip_unmap:
|
|
if (!page_mapped(page))
|
|
rc = move_to_new_page(newpage, page, remap_swapcache, mode);
|
|
|
|
if (rc && remap_swapcache)
|
|
remove_migration_ptes(page, page);
|
|
|
|
/* Drop an anon_vma reference if we took one */
|
|
if (anon_vma)
|
|
put_anon_vma(anon_vma);
|
|
|
|
uncharge:
|
|
mem_cgroup_end_migration(mem, page, newpage,
|
|
(rc == MIGRATEPAGE_SUCCESS ||
|
|
rc == MIGRATEPAGE_BALLOON_SUCCESS));
|
|
unlock_page(page);
|
|
out:
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Obtain the lock on page, remove all ptes and migrate the page
|
|
* to the newly allocated page in newpage.
|
|
*/
|
|
static int unmap_and_move(new_page_t get_new_page, unsigned long private,
|
|
struct page *page, int force, enum migrate_mode mode)
|
|
{
|
|
int rc = 0;
|
|
int *result = NULL;
|
|
struct page *newpage = get_new_page(page, private, &result);
|
|
|
|
if (!newpage)
|
|
return -ENOMEM;
|
|
|
|
if (page_count(page) == 1) {
|
|
/* page was freed from under us. So we are done. */
|
|
goto out;
|
|
}
|
|
|
|
if (unlikely(PageTransHuge(page)))
|
|
if (unlikely(split_huge_page(page)))
|
|
goto out;
|
|
|
|
rc = __unmap_and_move(page, newpage, force, mode);
|
|
|
|
if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
|
|
/*
|
|
* A ballooned page has been migrated already.
|
|
* Now, it's the time to wrap-up counters,
|
|
* handle the page back to Buddy and return.
|
|
*/
|
|
dec_zone_page_state(page, NR_ISOLATED_ANON +
|
|
page_is_file_cache(page));
|
|
balloon_page_free(page);
|
|
return MIGRATEPAGE_SUCCESS;
|
|
}
|
|
out:
|
|
if (rc != -EAGAIN) {
|
|
/*
|
|
* A page that has been migrated has all references
|
|
* removed and will be freed. A page that has not been
|
|
* migrated will have kepts its references and be
|
|
* restored.
|
|
*/
|
|
list_del(&page->lru);
|
|
dec_zone_page_state(page, NR_ISOLATED_ANON +
|
|
page_is_file_cache(page));
|
|
putback_lru_page(page);
|
|
}
|
|
/*
|
|
* Move the new page to the LRU. If migration was not successful
|
|
* then this will free the page.
|
|
*/
|
|
putback_lru_page(newpage);
|
|
if (result) {
|
|
if (rc)
|
|
*result = rc;
|
|
else
|
|
*result = page_to_nid(newpage);
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Counterpart of unmap_and_move_page() for hugepage migration.
|
|
*
|
|
* This function doesn't wait the completion of hugepage I/O
|
|
* because there is no race between I/O and migration for hugepage.
|
|
* Note that currently hugepage I/O occurs only in direct I/O
|
|
* where no lock is held and PG_writeback is irrelevant,
|
|
* and writeback status of all subpages are counted in the reference
|
|
* count of the head page (i.e. if all subpages of a 2MB hugepage are
|
|
* under direct I/O, the reference of the head page is 512 and a bit more.)
|
|
* This means that when we try to migrate hugepage whose subpages are
|
|
* doing direct I/O, some references remain after try_to_unmap() and
|
|
* hugepage migration fails without data corruption.
|
|
*
|
|
* There is also no race when direct I/O is issued on the page under migration,
|
|
* because then pte is replaced with migration swap entry and direct I/O code
|
|
* will wait in the page fault for migration to complete.
|
|
*/
|
|
static int unmap_and_move_huge_page(new_page_t get_new_page,
|
|
unsigned long private, struct page *hpage,
|
|
int force, enum migrate_mode mode)
|
|
{
|
|
int rc = 0;
|
|
int *result = NULL;
|
|
struct page *new_hpage = get_new_page(hpage, private, &result);
|
|
struct anon_vma *anon_vma = NULL;
|
|
|
|
if (!new_hpage)
|
|
return -ENOMEM;
|
|
|
|
rc = -EAGAIN;
|
|
|
|
if (!trylock_page(hpage)) {
|
|
if (!force || mode != MIGRATE_SYNC)
|
|
goto out;
|
|
lock_page(hpage);
|
|
}
|
|
|
|
if (PageAnon(hpage))
|
|
anon_vma = page_get_anon_vma(hpage);
|
|
|
|
try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
|
|
|
|
if (!page_mapped(hpage))
|
|
rc = move_to_new_page(new_hpage, hpage, 1, mode);
|
|
|
|
if (rc)
|
|
remove_migration_ptes(hpage, hpage);
|
|
|
|
if (anon_vma)
|
|
put_anon_vma(anon_vma);
|
|
|
|
if (!rc)
|
|
hugetlb_cgroup_migrate(hpage, new_hpage);
|
|
|
|
unlock_page(hpage);
|
|
out:
|
|
put_page(new_hpage);
|
|
if (result) {
|
|
if (rc)
|
|
*result = rc;
|
|
else
|
|
*result = page_to_nid(new_hpage);
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* migrate_pages - migrate the pages specified in a list, to the free pages
|
|
* supplied as the target for the page migration
|
|
*
|
|
* @from: The list of pages to be migrated.
|
|
* @get_new_page: The function used to allocate free pages to be used
|
|
* as the target of the page migration.
|
|
* @private: Private data to be passed on to get_new_page()
|
|
* @mode: The migration mode that specifies the constraints for
|
|
* page migration, if any.
|
|
* @reason: The reason for page migration.
|
|
*
|
|
* The function returns after 10 attempts or if no pages are movable any more
|
|
* because the list has become empty or no retryable pages exist any more.
|
|
* The caller should call putback_lru_pages() to return pages to the LRU
|
|
* or free list only if ret != 0.
|
|
*
|
|
* Returns the number of pages that were not migrated, or an error code.
|
|
*/
|
|
int migrate_pages(struct list_head *from, new_page_t get_new_page,
|
|
unsigned long private, enum migrate_mode mode, int reason)
|
|
{
|
|
int retry = 1;
|
|
int nr_failed = 0;
|
|
int nr_succeeded = 0;
|
|
int pass = 0;
|
|
struct page *page;
|
|
struct page *page2;
|
|
int swapwrite = current->flags & PF_SWAPWRITE;
|
|
int rc;
|
|
|
|
if (!swapwrite)
|
|
current->flags |= PF_SWAPWRITE;
|
|
|
|
for(pass = 0; pass < 10 && retry; pass++) {
|
|
retry = 0;
|
|
|
|
list_for_each_entry_safe(page, page2, from, lru) {
|
|
cond_resched();
|
|
|
|
rc = unmap_and_move(get_new_page, private,
|
|
page, pass > 2, mode);
|
|
|
|
switch(rc) {
|
|
case -ENOMEM:
|
|
goto out;
|
|
case -EAGAIN:
|
|
retry++;
|
|
break;
|
|
case MIGRATEPAGE_SUCCESS:
|
|
nr_succeeded++;
|
|
break;
|
|
default:
|
|
/* Permanent failure */
|
|
nr_failed++;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
rc = nr_failed + retry;
|
|
out:
|
|
if (nr_succeeded)
|
|
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
|
|
if (nr_failed)
|
|
count_vm_events(PGMIGRATE_FAIL, nr_failed);
|
|
trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
|
|
|
|
if (!swapwrite)
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
|
|
return rc;
|
|
}
|
|
|
|
int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
|
|
unsigned long private, enum migrate_mode mode)
|
|
{
|
|
int pass, rc;
|
|
|
|
for (pass = 0; pass < 10; pass++) {
|
|
rc = unmap_and_move_huge_page(get_new_page, private,
|
|
hpage, pass > 2, mode);
|
|
switch (rc) {
|
|
case -ENOMEM:
|
|
goto out;
|
|
case -EAGAIN:
|
|
/* try again */
|
|
cond_resched();
|
|
break;
|
|
case MIGRATEPAGE_SUCCESS:
|
|
goto out;
|
|
default:
|
|
rc = -EIO;
|
|
goto out;
|
|
}
|
|
}
|
|
out:
|
|
return rc;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA
|
|
/*
|
|
* Move a list of individual pages
|
|
*/
|
|
struct page_to_node {
|
|
unsigned long addr;
|
|
struct page *page;
|
|
int node;
|
|
int status;
|
|
};
|
|
|
|
static struct page *new_page_node(struct page *p, unsigned long private,
|
|
int **result)
|
|
{
|
|
struct page_to_node *pm = (struct page_to_node *)private;
|
|
|
|
while (pm->node != MAX_NUMNODES && pm->page != p)
|
|
pm++;
|
|
|
|
if (pm->node == MAX_NUMNODES)
|
|
return NULL;
|
|
|
|
*result = &pm->status;
|
|
|
|
return alloc_pages_exact_node(pm->node,
|
|
GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
|
|
}
|
|
|
|
/*
|
|
* Move a set of pages as indicated in the pm array. The addr
|
|
* field must be set to the virtual address of the page to be moved
|
|
* and the node number must contain a valid target node.
|
|
* The pm array ends with node = MAX_NUMNODES.
|
|
*/
|
|
static int do_move_page_to_node_array(struct mm_struct *mm,
|
|
struct page_to_node *pm,
|
|
int migrate_all)
|
|
{
|
|
int err;
|
|
struct page_to_node *pp;
|
|
LIST_HEAD(pagelist);
|
|
|
|
down_read(&mm->mmap_sem);
|
|
|
|
/*
|
|
* Build a list of pages to migrate
|
|
*/
|
|
for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
|
|
struct vm_area_struct *vma;
|
|
struct page *page;
|
|
|
|
err = -EFAULT;
|
|
vma = find_vma(mm, pp->addr);
|
|
if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
|
|
goto set_status;
|
|
|
|
page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
|
|
|
|
err = PTR_ERR(page);
|
|
if (IS_ERR(page))
|
|
goto set_status;
|
|
|
|
err = -ENOENT;
|
|
if (!page)
|
|
goto set_status;
|
|
|
|
/* Use PageReserved to check for zero page */
|
|
if (PageReserved(page))
|
|
goto put_and_set;
|
|
|
|
pp->page = page;
|
|
err = page_to_nid(page);
|
|
|
|
if (err == pp->node)
|
|
/*
|
|
* Node already in the right place
|
|
*/
|
|
goto put_and_set;
|
|
|
|
err = -EACCES;
|
|
if (page_mapcount(page) > 1 &&
|
|
!migrate_all)
|
|
goto put_and_set;
|
|
|
|
err = isolate_lru_page(page);
|
|
if (!err) {
|
|
list_add_tail(&page->lru, &pagelist);
|
|
inc_zone_page_state(page, NR_ISOLATED_ANON +
|
|
page_is_file_cache(page));
|
|
}
|
|
put_and_set:
|
|
/*
|
|
* Either remove the duplicate refcount from
|
|
* isolate_lru_page() or drop the page ref if it was
|
|
* not isolated.
|
|
*/
|
|
put_page(page);
|
|
set_status:
|
|
pp->status = err;
|
|
}
|
|
|
|
err = 0;
|
|
if (!list_empty(&pagelist)) {
|
|
err = migrate_pages(&pagelist, new_page_node,
|
|
(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
|
|
if (err)
|
|
putback_lru_pages(&pagelist);
|
|
}
|
|
|
|
up_read(&mm->mmap_sem);
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* Migrate an array of page address onto an array of nodes and fill
|
|
* the corresponding array of status.
|
|
*/
|
|
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
|
|
unsigned long nr_pages,
|
|
const void __user * __user *pages,
|
|
const int __user *nodes,
|
|
int __user *status, int flags)
|
|
{
|
|
struct page_to_node *pm;
|
|
unsigned long chunk_nr_pages;
|
|
unsigned long chunk_start;
|
|
int err;
|
|
|
|
err = -ENOMEM;
|
|
pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
|
|
if (!pm)
|
|
goto out;
|
|
|
|
migrate_prep();
|
|
|
|
/*
|
|
* Store a chunk of page_to_node array in a page,
|
|
* but keep the last one as a marker
|
|
*/
|
|
chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
|
|
|
|
for (chunk_start = 0;
|
|
chunk_start < nr_pages;
|
|
chunk_start += chunk_nr_pages) {
|
|
int j;
|
|
|
|
if (chunk_start + chunk_nr_pages > nr_pages)
|
|
chunk_nr_pages = nr_pages - chunk_start;
|
|
|
|
/* fill the chunk pm with addrs and nodes from user-space */
|
|
for (j = 0; j < chunk_nr_pages; j++) {
|
|
const void __user *p;
|
|
int node;
|
|
|
|
err = -EFAULT;
|
|
if (get_user(p, pages + j + chunk_start))
|
|
goto out_pm;
|
|
pm[j].addr = (unsigned long) p;
|
|
|
|
if (get_user(node, nodes + j + chunk_start))
|
|
goto out_pm;
|
|
|
|
err = -ENODEV;
|
|
if (node < 0 || node >= MAX_NUMNODES)
|
|
goto out_pm;
|
|
|
|
if (!node_state(node, N_MEMORY))
|
|
goto out_pm;
|
|
|
|
err = -EACCES;
|
|
if (!node_isset(node, task_nodes))
|
|
goto out_pm;
|
|
|
|
pm[j].node = node;
|
|
}
|
|
|
|
/* End marker for this chunk */
|
|
pm[chunk_nr_pages].node = MAX_NUMNODES;
|
|
|
|
/* Migrate this chunk */
|
|
err = do_move_page_to_node_array(mm, pm,
|
|
flags & MPOL_MF_MOVE_ALL);
|
|
if (err < 0)
|
|
goto out_pm;
|
|
|
|
/* Return status information */
|
|
for (j = 0; j < chunk_nr_pages; j++)
|
|
if (put_user(pm[j].status, status + j + chunk_start)) {
|
|
err = -EFAULT;
|
|
goto out_pm;
|
|
}
|
|
}
|
|
err = 0;
|
|
|
|
out_pm:
|
|
free_page((unsigned long)pm);
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* Determine the nodes of an array of pages and store it in an array of status.
|
|
*/
|
|
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
|
|
const void __user **pages, int *status)
|
|
{
|
|
unsigned long i;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
unsigned long addr = (unsigned long)(*pages);
|
|
struct vm_area_struct *vma;
|
|
struct page *page;
|
|
int err = -EFAULT;
|
|
|
|
vma = find_vma(mm, addr);
|
|
if (!vma || addr < vma->vm_start)
|
|
goto set_status;
|
|
|
|
page = follow_page(vma, addr, 0);
|
|
|
|
err = PTR_ERR(page);
|
|
if (IS_ERR(page))
|
|
goto set_status;
|
|
|
|
err = -ENOENT;
|
|
/* Use PageReserved to check for zero page */
|
|
if (!page || PageReserved(page))
|
|
goto set_status;
|
|
|
|
err = page_to_nid(page);
|
|
set_status:
|
|
*status = err;
|
|
|
|
pages++;
|
|
status++;
|
|
}
|
|
|
|
up_read(&mm->mmap_sem);
|
|
}
|
|
|
|
/*
|
|
* Determine the nodes of a user array of pages and store it in
|
|
* a user array of status.
|
|
*/
|
|
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
|
|
const void __user * __user *pages,
|
|
int __user *status)
|
|
{
|
|
#define DO_PAGES_STAT_CHUNK_NR 16
|
|
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
|
|
int chunk_status[DO_PAGES_STAT_CHUNK_NR];
|
|
|
|
while (nr_pages) {
|
|
unsigned long chunk_nr;
|
|
|
|
chunk_nr = nr_pages;
|
|
if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
|
|
chunk_nr = DO_PAGES_STAT_CHUNK_NR;
|
|
|
|
if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
|
|
break;
|
|
|
|
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
|
|
|
|
if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
|
|
break;
|
|
|
|
pages += chunk_nr;
|
|
status += chunk_nr;
|
|
nr_pages -= chunk_nr;
|
|
}
|
|
return nr_pages ? -EFAULT : 0;
|
|
}
|
|
|
|
/*
|
|
* Move a list of pages in the address space of the currently executing
|
|
* process.
|
|
*/
|
|
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
|
|
const void __user * __user *, pages,
|
|
const int __user *, nodes,
|
|
int __user *, status, int, flags)
|
|
{
|
|
const struct cred *cred = current_cred(), *tcred;
|
|
struct task_struct *task;
|
|
struct mm_struct *mm;
|
|
int err;
|
|
nodemask_t task_nodes;
|
|
|
|
/* Check flags */
|
|
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
|
|
return -EINVAL;
|
|
|
|
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
|
|
return -EPERM;
|
|
|
|
/* Find the mm_struct */
|
|
rcu_read_lock();
|
|
task = pid ? find_task_by_vpid(pid) : current;
|
|
if (!task) {
|
|
rcu_read_unlock();
|
|
return -ESRCH;
|
|
}
|
|
get_task_struct(task);
|
|
|
|
/*
|
|
* Check if this process has the right to modify the specified
|
|
* process. The right exists if the process has administrative
|
|
* capabilities, superuser privileges or the same
|
|
* userid as the target process.
|
|
*/
|
|
tcred = __task_cred(task);
|
|
if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
|
|
!uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
|
|
!capable(CAP_SYS_NICE)) {
|
|
rcu_read_unlock();
|
|
err = -EPERM;
|
|
goto out;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
err = security_task_movememory(task);
|
|
if (err)
|
|
goto out;
|
|
|
|
task_nodes = cpuset_mems_allowed(task);
|
|
mm = get_task_mm(task);
|
|
put_task_struct(task);
|
|
|
|
if (!mm)
|
|
return -EINVAL;
|
|
|
|
if (nodes)
|
|
err = do_pages_move(mm, task_nodes, nr_pages, pages,
|
|
nodes, status, flags);
|
|
else
|
|
err = do_pages_stat(mm, nr_pages, pages, status);
|
|
|
|
mmput(mm);
|
|
return err;
|
|
|
|
out:
|
|
put_task_struct(task);
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* Call migration functions in the vma_ops that may prepare
|
|
* memory in a vm for migration. migration functions may perform
|
|
* the migration for vmas that do not have an underlying page struct.
|
|
*/
|
|
int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
|
|
const nodemask_t *from, unsigned long flags)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
int err = 0;
|
|
|
|
for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
|
|
if (vma->vm_ops && vma->vm_ops->migrate) {
|
|
err = vma->vm_ops->migrate(vma, to, from, flags);
|
|
if (err)
|
|
break;
|
|
}
|
|
}
|
|
return err;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA_BALANCING
|
|
/*
|
|
* Returns true if this is a safe migration target node for misplaced NUMA
|
|
* pages. Currently it only checks the watermarks which crude
|
|
*/
|
|
static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
|
|
unsigned long nr_migrate_pages)
|
|
{
|
|
int z;
|
|
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
|
|
struct zone *zone = pgdat->node_zones + z;
|
|
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
if (zone->all_unreclaimable)
|
|
continue;
|
|
|
|
/* Avoid waking kswapd by allocating pages_to_migrate pages. */
|
|
if (!zone_watermark_ok(zone, 0,
|
|
high_wmark_pages(zone) +
|
|
nr_migrate_pages,
|
|
0, 0))
|
|
continue;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static struct page *alloc_misplaced_dst_page(struct page *page,
|
|
unsigned long data,
|
|
int **result)
|
|
{
|
|
int nid = (int) data;
|
|
struct page *newpage;
|
|
|
|
newpage = alloc_pages_exact_node(nid,
|
|
(GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
|
|
__GFP_NOMEMALLOC | __GFP_NORETRY |
|
|
__GFP_NOWARN) &
|
|
~GFP_IOFS, 0);
|
|
if (newpage)
|
|
page_nid_xchg_last(newpage, page_nid_last(page));
|
|
|
|
return newpage;
|
|
}
|
|
|
|
/*
|
|
* page migration rate limiting control.
|
|
* Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
|
|
* window of time. Default here says do not migrate more than 1280M per second.
|
|
* If a node is rate-limited then PTE NUMA updates are also rate-limited. However
|
|
* as it is faults that reset the window, pte updates will happen unconditionally
|
|
* if there has not been a fault since @pteupdate_interval_millisecs after the
|
|
* throttle window closed.
|
|
*/
|
|
static unsigned int migrate_interval_millisecs __read_mostly = 100;
|
|
static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
|
|
static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
|
|
|
|
/* Returns true if NUMA migration is currently rate limited */
|
|
bool migrate_ratelimited(int node)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(node);
|
|
|
|
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
|
|
msecs_to_jiffies(pteupdate_interval_millisecs)))
|
|
return false;
|
|
|
|
if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Returns true if the node is migrate rate-limited after the update */
|
|
bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages)
|
|
{
|
|
bool rate_limited = false;
|
|
|
|
/*
|
|
* Rate-limit the amount of data that is being migrated to a node.
|
|
* Optimal placement is no good if the memory bus is saturated and
|
|
* all the time is being spent migrating!
|
|
*/
|
|
spin_lock(&pgdat->numabalancing_migrate_lock);
|
|
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
|
|
pgdat->numabalancing_migrate_nr_pages = 0;
|
|
pgdat->numabalancing_migrate_next_window = jiffies +
|
|
msecs_to_jiffies(migrate_interval_millisecs);
|
|
}
|
|
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
|
|
rate_limited = true;
|
|
else
|
|
pgdat->numabalancing_migrate_nr_pages += nr_pages;
|
|
spin_unlock(&pgdat->numabalancing_migrate_lock);
|
|
|
|
return rate_limited;
|
|
}
|
|
|
|
int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
|
|
{
|
|
int page_lru;
|
|
|
|
VM_BUG_ON(compound_order(page) && !PageTransHuge(page));
|
|
|
|
/* Avoid migrating to a node that is nearly full */
|
|
if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
|
|
return 0;
|
|
|
|
if (isolate_lru_page(page))
|
|
return 0;
|
|
|
|
/*
|
|
* migrate_misplaced_transhuge_page() skips page migration's usual
|
|
* check on page_count(), so we must do it here, now that the page
|
|
* has been isolated: a GUP pin, or any other pin, prevents migration.
|
|
* The expected page count is 3: 1 for page's mapcount and 1 for the
|
|
* caller's pin and 1 for the reference taken by isolate_lru_page().
|
|
*/
|
|
if (PageTransHuge(page) && page_count(page) != 3) {
|
|
putback_lru_page(page);
|
|
return 0;
|
|
}
|
|
|
|
page_lru = page_is_file_cache(page);
|
|
mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
|
|
hpage_nr_pages(page));
|
|
|
|
/*
|
|
* Isolating the page has taken another reference, so the
|
|
* caller's reference can be safely dropped without the page
|
|
* disappearing underneath us during migration.
|
|
*/
|
|
put_page(page);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Attempt to migrate a misplaced page to the specified destination
|
|
* node. Caller is expected to have an elevated reference count on
|
|
* the page that will be dropped by this function before returning.
|
|
*/
|
|
int migrate_misplaced_page(struct page *page, int node)
|
|
{
|
|
pg_data_t *pgdat = NODE_DATA(node);
|
|
int isolated;
|
|
int nr_remaining;
|
|
LIST_HEAD(migratepages);
|
|
|
|
/*
|
|
* Don't migrate pages that are mapped in multiple processes.
|
|
* TODO: Handle false sharing detection instead of this hammer
|
|
*/
|
|
if (page_mapcount(page) != 1)
|
|
goto out;
|
|
|
|
/*
|
|
* Rate-limit the amount of data that is being migrated to a node.
|
|
* Optimal placement is no good if the memory bus is saturated and
|
|
* all the time is being spent migrating!
|
|
*/
|
|
if (numamigrate_update_ratelimit(pgdat, 1))
|
|
goto out;
|
|
|
|
isolated = numamigrate_isolate_page(pgdat, page);
|
|
if (!isolated)
|
|
goto out;
|
|
|
|
list_add(&page->lru, &migratepages);
|
|
nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
|
|
node, MIGRATE_ASYNC, MR_NUMA_MISPLACED);
|
|
if (nr_remaining) {
|
|
putback_lru_pages(&migratepages);
|
|
isolated = 0;
|
|
} else
|
|
count_vm_numa_event(NUMA_PAGE_MIGRATE);
|
|
BUG_ON(!list_empty(&migratepages));
|
|
return isolated;
|
|
|
|
out:
|
|
put_page(page);
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
|
|
/*
|
|
* Migrates a THP to a given target node. page must be locked and is unlocked
|
|
* before returning.
|
|
*/
|
|
int migrate_misplaced_transhuge_page(struct mm_struct *mm,
|
|
struct vm_area_struct *vma,
|
|
pmd_t *pmd, pmd_t entry,
|
|
unsigned long address,
|
|
struct page *page, int node)
|
|
{
|
|
unsigned long haddr = address & HPAGE_PMD_MASK;
|
|
pg_data_t *pgdat = NODE_DATA(node);
|
|
int isolated = 0;
|
|
struct page *new_page = NULL;
|
|
struct mem_cgroup *memcg = NULL;
|
|
int page_lru = page_is_file_cache(page);
|
|
|
|
/*
|
|
* Don't migrate pages that are mapped in multiple processes.
|
|
* TODO: Handle false sharing detection instead of this hammer
|
|
*/
|
|
if (page_mapcount(page) != 1)
|
|
goto out_dropref;
|
|
|
|
/*
|
|
* Rate-limit the amount of data that is being migrated to a node.
|
|
* Optimal placement is no good if the memory bus is saturated and
|
|
* all the time is being spent migrating!
|
|
*/
|
|
if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
|
|
goto out_dropref;
|
|
|
|
new_page = alloc_pages_node(node,
|
|
(GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
|
|
if (!new_page)
|
|
goto out_fail;
|
|
|
|
page_nid_xchg_last(new_page, page_nid_last(page));
|
|
|
|
isolated = numamigrate_isolate_page(pgdat, page);
|
|
if (!isolated) {
|
|
put_page(new_page);
|
|
goto out_fail;
|
|
}
|
|
|
|
/* Prepare a page as a migration target */
|
|
__set_page_locked(new_page);
|
|
SetPageSwapBacked(new_page);
|
|
|
|
/* anon mapping, we can simply copy page->mapping to the new page: */
|
|
new_page->mapping = page->mapping;
|
|
new_page->index = page->index;
|
|
migrate_page_copy(new_page, page);
|
|
WARN_ON(PageLRU(new_page));
|
|
|
|
/* Recheck the target PMD */
|
|
spin_lock(&mm->page_table_lock);
|
|
if (unlikely(!pmd_same(*pmd, entry))) {
|
|
spin_unlock(&mm->page_table_lock);
|
|
|
|
/* Reverse changes made by migrate_page_copy() */
|
|
if (TestClearPageActive(new_page))
|
|
SetPageActive(page);
|
|
if (TestClearPageUnevictable(new_page))
|
|
SetPageUnevictable(page);
|
|
mlock_migrate_page(page, new_page);
|
|
|
|
unlock_page(new_page);
|
|
put_page(new_page); /* Free it */
|
|
|
|
unlock_page(page);
|
|
putback_lru_page(page);
|
|
|
|
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
|
|
isolated = 0;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Traditional migration needs to prepare the memcg charge
|
|
* transaction early to prevent the old page from being
|
|
* uncharged when installing migration entries. Here we can
|
|
* save the potential rollback and start the charge transfer
|
|
* only when migration is already known to end successfully.
|
|
*/
|
|
mem_cgroup_prepare_migration(page, new_page, &memcg);
|
|
|
|
entry = mk_pmd(new_page, vma->vm_page_prot);
|
|
entry = pmd_mknonnuma(entry);
|
|
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
|
|
entry = pmd_mkhuge(entry);
|
|
|
|
page_add_new_anon_rmap(new_page, vma, haddr);
|
|
|
|
set_pmd_at(mm, haddr, pmd, entry);
|
|
update_mmu_cache_pmd(vma, address, &entry);
|
|
page_remove_rmap(page);
|
|
/*
|
|
* Finish the charge transaction under the page table lock to
|
|
* prevent split_huge_page() from dividing up the charge
|
|
* before it's fully transferred to the new page.
|
|
*/
|
|
mem_cgroup_end_migration(memcg, page, new_page, true);
|
|
spin_unlock(&mm->page_table_lock);
|
|
|
|
unlock_page(new_page);
|
|
unlock_page(page);
|
|
put_page(page); /* Drop the rmap reference */
|
|
put_page(page); /* Drop the LRU isolation reference */
|
|
|
|
count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
|
|
count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
|
|
|
|
out:
|
|
mod_zone_page_state(page_zone(page),
|
|
NR_ISOLATED_ANON + page_lru,
|
|
-HPAGE_PMD_NR);
|
|
return isolated;
|
|
|
|
out_fail:
|
|
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
|
|
out_dropref:
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_NUMA_BALANCING */
|
|
|
|
#endif /* CONFIG_NUMA */
|