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aaa994b300
Do not leave pages on the lists passed to migrate_pages(). Seems that we will not need any postprocessing of pages. This will simplify the handling of pages by the callers of migrate_pages(). Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Jes Sorensen <jes@trained-monkey.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
764 lines
17 KiB
C
764 lines
17 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 <clameter@sgi.com>
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*/
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#include <linux/migrate.h>
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#include <linux/module.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/pagevec.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 "internal.h"
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/* The maximum number of pages to take off the LRU for migration */
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#define MIGRATE_CHUNK_SIZE 256
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#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
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/*
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* Isolate one page from the LRU lists. If successful put it onto
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* the indicated list with elevated page count.
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*
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* Result:
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* -EBUSY: page not on LRU list
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* 0: page removed from LRU list and added to the specified list.
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*/
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int isolate_lru_page(struct page *page, struct list_head *pagelist)
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{
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int ret = -EBUSY;
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if (PageLRU(page)) {
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struct zone *zone = page_zone(page);
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spin_lock_irq(&zone->lru_lock);
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if (PageLRU(page)) {
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ret = 0;
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get_page(page);
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ClearPageLRU(page);
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if (PageActive(page))
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del_page_from_active_list(zone, page);
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else
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del_page_from_inactive_list(zone, page);
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list_add_tail(&page->lru, pagelist);
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}
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spin_unlock_irq(&zone->lru_lock);
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}
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return ret;
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}
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/*
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* migrate_prep() needs to be called after we have compiled the list of pages
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* to be migrated using isolate_lru_page() but before we begin a series of calls
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* to migrate_pages().
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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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static inline void move_to_lru(struct page *page)
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{
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if (PageActive(page)) {
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/*
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* lru_cache_add_active checks that
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* the PG_active bit is off.
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*/
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ClearPageActive(page);
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lru_cache_add_active(page);
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} else {
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lru_cache_add(page);
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}
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put_page(page);
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}
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/*
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* Add isolated pages on the list back to the LRU.
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*
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* returns the number of pages put back.
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*/
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int 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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int count = 0;
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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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move_to_lru(page);
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count++;
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}
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return count;
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}
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static inline int is_swap_pte(pte_t pte)
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{
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return !pte_none(pte) && !pte_present(pte) && !pte_file(pte);
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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 void remove_migration_pte(struct vm_area_struct *vma,
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struct page *old, struct page *new)
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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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pgd_t *pgd;
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pud_t *pud;
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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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unsigned long addr = page_address_in_vma(new, vma);
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if (addr == -EFAULT)
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return;
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pgd = pgd_offset(mm, addr);
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if (!pgd_present(*pgd))
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return;
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pud = pud_offset(pgd, addr);
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if (!pud_present(*pud))
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return;
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pmd = pmd_offset(pud, addr);
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if (!pmd_present(*pmd))
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return;
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ptep = pte_offset_map(pmd, addr);
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if (!is_swap_pte(*ptep)) {
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pte_unmap(ptep);
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return;
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}
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ptl = pte_lockptr(mm, pmd);
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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 out;
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entry = pte_to_swp_entry(pte);
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if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
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goto out;
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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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set_pte_at(mm, addr, ptep, pte);
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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, pte);
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lazy_mmu_prot_update(pte);
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out:
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pte_unmap_unlock(ptep, ptl);
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}
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/*
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* Note that remove_file_migration_ptes will only work on regular mappings,
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* Nonlinear mappings do not use migration entries.
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*/
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static void remove_file_migration_ptes(struct page *old, struct page *new)
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{
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struct vm_area_struct *vma;
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struct address_space *mapping = page_mapping(new);
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struct prio_tree_iter iter;
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pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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if (!mapping)
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return;
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spin_lock(&mapping->i_mmap_lock);
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vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
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remove_migration_pte(vma, old, new);
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spin_unlock(&mapping->i_mmap_lock);
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}
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/*
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* Must hold mmap_sem lock on at least one of the vmas containing
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* the page so that the anon_vma cannot vanish.
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*/
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static void remove_anon_migration_ptes(struct page *old, struct page *new)
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{
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struct anon_vma *anon_vma;
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struct vm_area_struct *vma;
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unsigned long mapping;
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mapping = (unsigned long)new->mapping;
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if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
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return;
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/*
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* We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
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*/
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anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
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spin_lock(&anon_vma->lock);
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list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
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remove_migration_pte(vma, old, new);
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spin_unlock(&anon_vma->lock);
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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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if (PageAnon(new))
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remove_anon_migration_ptes(old, new);
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else
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remove_file_migration_ptes(old, new);
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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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* This function is called from do_swap_page().
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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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get_page(page);
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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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/*
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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 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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{
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struct page **radix_pointer;
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if (!mapping) {
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/* Anonymous page */
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if (page_count(page) != 1)
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return -EAGAIN;
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return 0;
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}
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write_lock_irq(&mapping->tree_lock);
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radix_pointer = (struct page **)radix_tree_lookup_slot(
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&mapping->page_tree,
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page_index(page));
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if (page_count(page) != 2 + !!PagePrivate(page) ||
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*radix_pointer != page) {
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write_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);
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#ifdef CONFIG_SWAP
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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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#endif
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*radix_pointer = newpage;
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__put_page(page);
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write_unlock_irq(&mapping->tree_lock);
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return 0;
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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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static void migrate_page_copy(struct page *newpage, struct page *page)
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{
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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 (PageActive(page))
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SetPageActive(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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if (PageDirty(page)) {
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clear_page_dirty_for_io(page);
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set_page_dirty(newpage);
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}
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#ifdef CONFIG_SWAP
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ClearPageSwapCache(page);
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#endif
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ClearPageActive(page);
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ClearPagePrivate(page);
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set_page_private(page, 0);
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page->mapping = NULL;
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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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}
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/************************************************************
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* Migration functions
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***********************************************************/
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/* Always fail migration. Used for mappings that are not movable */
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int fail_migrate_page(struct address_space *mapping,
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struct page *newpage, struct page *page)
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{
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return -EIO;
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}
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EXPORT_SYMBOL(fail_migrate_page);
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/*
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* Common logic to directly migrate a single page suitable for
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* pages that do not use PagePrivate.
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*
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* Pages are locked upon entry and exit.
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*/
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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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{
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int rc;
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BUG_ON(PageWriteback(page)); /* Writeback must be complete */
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rc = migrate_page_move_mapping(mapping, newpage, page);
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if (rc)
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return rc;
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migrate_page_copy(newpage, page);
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return 0;
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}
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EXPORT_SYMBOL(migrate_page);
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/*
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* Migration function for pages with buffers. This function can only be used
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* if the underlying filesystem guarantees that no other references to "page"
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* exist.
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*/
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int buffer_migrate_page(struct address_space *mapping,
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struct page *newpage, struct page *page)
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{
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struct buffer_head *bh, *head;
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int rc;
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if (!page_has_buffers(page))
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return migrate_page(mapping, newpage, page);
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head = page_buffers(page);
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rc = migrate_page_move_mapping(mapping, newpage, page);
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if (rc)
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return rc;
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bh = head;
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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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ClearPagePrivate(page);
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set_page_private(newpage, page_private(page));
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set_page_private(page, 0);
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put_page(page);
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get_page(newpage);
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bh = head;
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do {
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set_bh_page(bh, newpage, bh_offset(bh));
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bh = bh->b_this_page;
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} while (bh != head);
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SetPagePrivate(newpage);
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migrate_page_copy(newpage, page);
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bh = head;
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do {
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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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} while (bh != head);
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return 0;
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}
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EXPORT_SYMBOL(buffer_migrate_page);
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/*
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* Writeback a page to clean the dirty state
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*/
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static int writeout(struct address_space *mapping, struct page *page)
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{
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_NONE,
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.nr_to_write = 1,
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.range_start = 0,
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.range_end = LLONG_MAX,
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.nonblocking = 1,
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.for_reclaim = 1
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};
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int rc;
|
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|
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if (!mapping->a_ops->writepage)
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/* No write method for the address space */
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return -EINVAL;
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|
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if (!clear_page_dirty_for_io(page))
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/* Someone else already triggered a write */
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return -EAGAIN;
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|
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/*
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* A dirty page may imply that the underlying filesystem has
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* the page on some queue. So the page must be clean for
|
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* migration. Writeout may mean we loose the lock and the
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* page state is no longer what we checked for earlier.
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* At this point we know that the migration attempt cannot
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* be successful.
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*/
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remove_migration_ptes(page, page);
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rc = mapping->a_ops->writepage(page, &wbc);
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if (rc < 0)
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/* I/O Error writing */
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return -EIO;
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|
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if (rc != AOP_WRITEPAGE_ACTIVATE)
|
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/* unlocked. Relock */
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lock_page(page);
|
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|
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return -EAGAIN;
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}
|
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|
|
/*
|
|
* Default handling if a filesystem does not provide a migration function.
|
|
*/
|
|
static int fallback_migrate_page(struct address_space *mapping,
|
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struct page *newpage, struct page *page)
|
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{
|
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if (PageDirty(page))
|
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return writeout(mapping, page);
|
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|
|
/*
|
|
* Buffers may be managed in a filesystem specific way.
|
|
* We must have no buffers or drop them.
|
|
*/
|
|
if (page_has_buffers(page) &&
|
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!try_to_release_page(page, GFP_KERNEL))
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return -EAGAIN;
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|
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return migrate_page(mapping, newpage, page);
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}
|
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|
|
/*
|
|
* 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.
|
|
*/
|
|
static int move_to_new_page(struct page *newpage, struct page *page)
|
|
{
|
|
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 (TestSetPageLocked(newpage))
|
|
BUG();
|
|
|
|
/* Prepare mapping for the new page.*/
|
|
newpage->index = page->index;
|
|
newpage->mapping = page->mapping;
|
|
|
|
mapping = page_mapping(page);
|
|
if (!mapping)
|
|
rc = migrate_page(mapping, newpage, page);
|
|
else if (mapping->a_ops->migratepage)
|
|
/*
|
|
* Most pages have a mapping and most filesystems
|
|
* should provide a migration function. Anonymous
|
|
* pages are part of swap space which also has its
|
|
* own migration function. This is the most common
|
|
* path for page migration.
|
|
*/
|
|
rc = mapping->a_ops->migratepage(mapping,
|
|
newpage, page);
|
|
else
|
|
rc = fallback_migrate_page(mapping, newpage, page);
|
|
|
|
if (!rc)
|
|
remove_migration_ptes(page, newpage);
|
|
else
|
|
newpage->mapping = NULL;
|
|
|
|
unlock_page(newpage);
|
|
|
|
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(struct page *newpage, struct page *page, int force)
|
|
{
|
|
int rc = 0;
|
|
|
|
if (page_count(page) == 1)
|
|
/* page was freed from under us. So we are done. */
|
|
goto ret;
|
|
|
|
rc = -EAGAIN;
|
|
if (TestSetPageLocked(page)) {
|
|
if (!force)
|
|
goto ret;
|
|
lock_page(page);
|
|
}
|
|
|
|
if (PageWriteback(page)) {
|
|
if (!force)
|
|
goto unlock;
|
|
wait_on_page_writeback(page);
|
|
}
|
|
|
|
/*
|
|
* Establish migration ptes or remove ptes
|
|
*/
|
|
if (try_to_unmap(page, 1) != SWAP_FAIL) {
|
|
if (!page_mapped(page))
|
|
rc = move_to_new_page(newpage, page);
|
|
} else
|
|
/* A vma has VM_LOCKED set -> permanent failure */
|
|
rc = -EPERM;
|
|
|
|
if (rc)
|
|
remove_migration_ptes(page, page);
|
|
unlock:
|
|
unlock_page(page);
|
|
ret:
|
|
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);
|
|
move_to_lru(page);
|
|
|
|
list_del(&newpage->lru);
|
|
move_to_lru(newpage);
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* migrate_pages
|
|
*
|
|
* Two lists are passed to this function. The first list
|
|
* contains the pages isolated from the LRU to be migrated.
|
|
* The second list contains new pages that the isolated pages
|
|
* can be moved to.
|
|
*
|
|
* The function returns after 10 attempts or if no pages
|
|
* are movable anymore because to has become empty
|
|
* or no retryable pages exist anymore. All pages will be
|
|
* retruned to the LRU or freed.
|
|
*
|
|
* Return: Number of pages not migrated.
|
|
*/
|
|
int migrate_pages(struct list_head *from, struct list_head *to)
|
|
{
|
|
int retry = 1;
|
|
int nr_failed = 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) {
|
|
|
|
if (list_empty(to))
|
|
break;
|
|
|
|
cond_resched();
|
|
|
|
rc = unmap_and_move(lru_to_page(to), page, pass > 2);
|
|
|
|
switch(rc) {
|
|
case -EAGAIN:
|
|
retry++;
|
|
break;
|
|
case 0:
|
|
break;
|
|
default:
|
|
/* Permanent failure */
|
|
nr_failed++;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!swapwrite)
|
|
current->flags &= ~PF_SWAPWRITE;
|
|
|
|
putback_lru_pages(from);
|
|
return nr_failed + retry;
|
|
}
|
|
|
|
/*
|
|
* Migrate the list 'pagelist' of pages to a certain destination.
|
|
*
|
|
* Specify destination with either non-NULL vma or dest_node >= 0
|
|
* Return the number of pages not migrated or error code
|
|
*/
|
|
int migrate_pages_to(struct list_head *pagelist,
|
|
struct vm_area_struct *vma, int dest)
|
|
{
|
|
LIST_HEAD(newlist);
|
|
int err = 0;
|
|
unsigned long offset = 0;
|
|
int nr_pages;
|
|
int nr_failed = 0;
|
|
struct page *page;
|
|
struct list_head *p;
|
|
|
|
redo:
|
|
nr_pages = 0;
|
|
list_for_each(p, pagelist) {
|
|
if (vma) {
|
|
/*
|
|
* The address passed to alloc_page_vma is used to
|
|
* generate the proper interleave behavior. We fake
|
|
* the address here by an increasing offset in order
|
|
* to get the proper distribution of pages.
|
|
*
|
|
* No decision has been made as to which page
|
|
* a certain old page is moved to so we cannot
|
|
* specify the correct address.
|
|
*/
|
|
page = alloc_page_vma(GFP_HIGHUSER, vma,
|
|
offset + vma->vm_start);
|
|
offset += PAGE_SIZE;
|
|
}
|
|
else
|
|
page = alloc_pages_node(dest, GFP_HIGHUSER, 0);
|
|
|
|
if (!page) {
|
|
err = -ENOMEM;
|
|
goto out;
|
|
}
|
|
list_add_tail(&page->lru, &newlist);
|
|
nr_pages++;
|
|
if (nr_pages > MIGRATE_CHUNK_SIZE)
|
|
break;
|
|
}
|
|
err = migrate_pages(pagelist, &newlist);
|
|
|
|
if (err >= 0) {
|
|
nr_failed += err;
|
|
if (list_empty(&newlist) && !list_empty(pagelist))
|
|
goto redo;
|
|
}
|
|
out:
|
|
|
|
/* Calculate number of leftover pages */
|
|
list_for_each(p, pagelist)
|
|
nr_failed++;
|
|
return nr_failed;
|
|
}
|