/* * Memory Migration functionality - linux/mm/migration.c * * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter * * Page migration was first developed in the context of the memory hotplug * project. The main authors of the migration code are: * * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> * Hirokazu Takahashi <taka@valinux.co.jp> * Dave Hansen <haveblue@us.ibm.com> * Christoph Lameter */ #include <linux/migrate.h> #include <linux/export.h> #include <linux/swap.h> #include <linux/swapops.h> #include <linux/pagemap.h> #include <linux/buffer_head.h> #include <linux/mm_inline.h> #include <linux/nsproxy.h> #include <linux/pagevec.h> #include <linux/ksm.h> #include <linux/rmap.h> #include <linux/topology.h> #include <linux/cpu.h> #include <linux/cpuset.h> #include <linux/writeback.h> #include <linux/mempolicy.h> #include <linux/vmalloc.h> #include <linux/security.h> #include <linux/memcontrol.h> #include <linux/syscalls.h> #include <linux/hugetlb.h> #include <linux/hugetlb_cgroup.h> #include <linux/gfp.h> #include <linux/balloon_compaction.h> #include <asm/tlbflush.h> #define CREATE_TRACE_POINTS #include <trace/events/migrate.h> #include "internal.h" /* * migrate_prep() needs to be called before we start compiling a list of pages * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is * undesirable, use migrate_prep_local() */ int migrate_prep(void) { /* * Clear the LRU lists so pages can be isolated. * Note that pages may be moved off the LRU after we have * drained them. Those pages will fail to migrate like other * pages that may be busy. */ lru_add_drain_all(); return 0; } /* Do the necessary work of migrate_prep but not if it involves other CPUs */ int migrate_prep_local(void) { lru_add_drain(); return 0; } /* * Add isolated pages on the list back to the LRU under page lock * to avoid leaking evictable pages back onto unevictable list. */ void putback_lru_pages(struct list_head *l) { struct page *page; struct page *page2; list_for_each_entry_safe(page, page2, l, lru) { list_del(&page->lru); dec_zone_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); putback_lru_page(page); } } /* * Put previously isolated pages back onto the appropriate lists * from where they were once taken off for compaction/migration. * * This function shall be used instead of putback_lru_pages(), * whenever the isolated pageset has been built by isolate_migratepages_range() */ void putback_movable_pages(struct list_head *l) { struct page *page; struct page *page2; list_for_each_entry_safe(page, page2, l, lru) { list_del(&page->lru); dec_zone_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); if (unlikely(balloon_page_movable(page))) balloon_page_putback(page); else putback_lru_page(page); } } /* * Restore a potential migration pte to a working pte entry */ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, unsigned long addr, void *old) { struct mm_struct *mm = vma->vm_mm; swp_entry_t entry; pmd_t *pmd; pte_t *ptep, pte; spinlock_t *ptl; if (unlikely(PageHuge(new))) { ptep = huge_pte_offset(mm, addr); if (!ptep) goto out; ptl = &mm->page_table_lock; } else { pmd = mm_find_pmd(mm, addr); if (!pmd) goto out; if (pmd_trans_huge(*pmd)) goto out; ptep = pte_offset_map(pmd, addr); /* * Peek to check is_swap_pte() before taking ptlock? No, we * can race mremap's move_ptes(), which skips anon_vma lock. */ ptl = pte_lockptr(mm, pmd); } spin_lock(ptl); pte = *ptep; if (!is_swap_pte(pte)) goto unlock; entry = pte_to_swp_entry(pte); if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) goto unlock; get_page(new); pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); if (is_write_migration_entry(entry)) pte = pte_mkwrite(pte); #ifdef CONFIG_HUGETLB_PAGE if (PageHuge(new)) pte = pte_mkhuge(pte); #endif flush_cache_page(vma, addr, pte_pfn(pte)); set_pte_at(mm, addr, ptep, pte); if (PageHuge(new)) { if (PageAnon(new)) hugepage_add_anon_rmap(new, vma, addr); else page_dup_rmap(new); } else if (PageAnon(new)) page_add_anon_rmap(new, vma, addr); else page_add_file_rmap(new); /* No need to invalidate - it was non-present before */ update_mmu_cache(vma, addr, ptep); unlock: pte_unmap_unlock(ptep, ptl); out: return SWAP_AGAIN; } /* * Get rid of all migration entries and replace them by * references to the indicated page. */ static void remove_migration_ptes(struct page *old, struct page *new) { rmap_walk(new, remove_migration_pte, old); } /* * Something used the pte of a page under migration. We need to * get to the page and wait until migration is finished. * When we return from this function the fault will be retried. */ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, unsigned long address) { pte_t *ptep, pte; spinlock_t *ptl; swp_entry_t entry; struct page *page; ptep = pte_offset_map_lock(mm, pmd, address, &ptl); pte = *ptep; if (!is_swap_pte(pte)) goto out; entry = pte_to_swp_entry(pte); if (!is_migration_entry(entry)) goto out; page = migration_entry_to_page(entry); /* * Once radix-tree replacement of page migration started, page_count * *must* be zero. And, we don't want to call wait_on_page_locked() * against a page without get_page(). * So, we use get_page_unless_zero(), here. Even failed, page fault * will occur again. */ if (!get_page_unless_zero(page)) goto out; pte_unmap_unlock(ptep, ptl); wait_on_page_locked(page); put_page(page); return; out: pte_unmap_unlock(ptep, ptl); } #ifdef CONFIG_BLOCK /* Returns true if all buffers are successfully locked */ static bool buffer_migrate_lock_buffers(struct buffer_head *head, enum migrate_mode mode) { struct buffer_head *bh = head; /* Simple case, sync compaction */ if (mode != MIGRATE_ASYNC) { do { get_bh(bh); lock_buffer(bh); bh = bh->b_this_page; } while (bh != head); return true; } /* async case, we cannot block on lock_buffer so use trylock_buffer */ do { get_bh(bh); if (!trylock_buffer(bh)) { /* * We failed to lock the buffer and cannot stall in * async migration. Release the taken locks */ struct buffer_head *failed_bh = bh; put_bh(failed_bh); bh = head; while (bh != failed_bh) { unlock_buffer(bh); put_bh(bh); bh = bh->b_this_page; } return false; } bh = bh->b_this_page; } while (bh != head); return true; } #else static inline bool buffer_migrate_lock_buffers(struct buffer_head *head, enum migrate_mode mode) { return true; } #endif /* CONFIG_BLOCK */ /* * Replace the page in the mapping. * * The number of remaining references must be: * 1 for anonymous pages without a mapping * 2 for pages with a mapping * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. */ static int migrate_page_move_mapping(struct address_space *mapping, struct page *newpage, struct page *page, struct buffer_head *head, enum migrate_mode mode) { int expected_count = 0; void **pslot; if (!mapping) { /* Anonymous page without mapping */ if (page_count(page) != 1) return -EAGAIN; return MIGRATEPAGE_SUCCESS; } spin_lock_irq(&mapping->tree_lock); pslot = radix_tree_lookup_slot(&mapping->page_tree, page_index(page)); expected_count = 2 + page_has_private(page); if (page_count(page) != expected_count || radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } if (!page_freeze_refs(page, expected_count)) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } /* * In the async migration case of moving a page with buffers, lock the * buffers using trylock before the mapping is moved. If the mapping * was moved, we later failed to lock the buffers and could not move * the mapping back due to an elevated page count, we would have to * block waiting on other references to be dropped. */ if (mode == MIGRATE_ASYNC && head && !buffer_migrate_lock_buffers(head, mode)) { page_unfreeze_refs(page, expected_count); spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } /* * Now we know that no one else is looking at the page. */ get_page(newpage); /* add cache reference */ if (PageSwapCache(page)) { SetPageSwapCache(newpage); set_page_private(newpage, page_private(page)); } radix_tree_replace_slot(pslot, newpage); /* * Drop cache reference from old page by unfreezing * to one less reference. * We know this isn't the last reference. */ page_unfreeze_refs(page, expected_count - 1); /* * If moved to a different zone then also account * the page for that zone. Other VM counters will be * taken care of when we establish references to the * new page and drop references to the old page. * * Note that anonymous pages are accounted for * via NR_FILE_PAGES and NR_ANON_PAGES if they * are mapped to swap space. */ __dec_zone_page_state(page, NR_FILE_PAGES); __inc_zone_page_state(newpage, NR_FILE_PAGES); if (!PageSwapCache(page) && PageSwapBacked(page)) { __dec_zone_page_state(page, NR_SHMEM); __inc_zone_page_state(newpage, NR_SHMEM); } spin_unlock_irq(&mapping->tree_lock); return MIGRATEPAGE_SUCCESS; } /* * The expected number of remaining references is the same as that * of migrate_page_move_mapping(). */ int migrate_huge_page_move_mapping(struct address_space *mapping, struct page *newpage, struct page *page) { int expected_count; void **pslot; if (!mapping) { if (page_count(page) != 1) return -EAGAIN; return MIGRATEPAGE_SUCCESS; } spin_lock_irq(&mapping->tree_lock); pslot = radix_tree_lookup_slot(&mapping->page_tree, page_index(page)); expected_count = 2 + page_has_private(page); if (page_count(page) != expected_count || radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } if (!page_freeze_refs(page, expected_count)) { spin_unlock_irq(&mapping->tree_lock); return -EAGAIN; } get_page(newpage); radix_tree_replace_slot(pslot, newpage); page_unfreeze_refs(page, expected_count - 1); spin_unlock_irq(&mapping->tree_lock); return MIGRATEPAGE_SUCCESS; } /* * Copy the page to its new location */ void migrate_page_copy(struct page *newpage, struct page *page) { if (PageHuge(page) || PageTransHuge(page)) copy_huge_page(newpage, page); else copy_highpage(newpage, page); if (PageError(page)) SetPageError(newpage); if (PageReferenced(page)) SetPageReferenced(newpage); if (PageUptodate(page)) SetPageUptodate(newpage); if (TestClearPageActive(page)) { VM_BUG_ON(PageUnevictable(page)); SetPageActive(newpage); } else if (TestClearPageUnevictable(page)) SetPageUnevictable(newpage); if (PageChecked(page)) SetPageChecked(newpage); if (PageMappedToDisk(page)) SetPageMappedToDisk(newpage); if (PageDirty(page)) { clear_page_dirty_for_io(page); /* * Want to mark the page and the radix tree as dirty, and * redo the accounting that clear_page_dirty_for_io undid, * but we can't use set_page_dirty because that function * is actually a signal that all of the page has become dirty. * Whereas only part of our page may be dirty. */ if (PageSwapBacked(page)) SetPageDirty(newpage); else __set_page_dirty_nobuffers(newpage); } mlock_migrate_page(newpage, page); ksm_migrate_page(newpage, page); ClearPageSwapCache(page); ClearPagePrivate(page); set_page_private(page, 0); /* * If any waiters have accumulated on the new page then * wake them up. */ if (PageWriteback(newpage)) end_page_writeback(newpage); } /************************************************************ * Migration functions ***********************************************************/ /* Always fail migration. Used for mappings that are not movable */ int fail_migrate_page(struct address_space *mapping, struct page *newpage, struct page *page) { return -EIO; } EXPORT_SYMBOL(fail_migrate_page); /* * Common logic to directly migrate a single page suitable for * pages that do not use PagePrivate/PagePrivate2. * * Pages are locked upon entry and exit. */ int migrate_page(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { int rc; BUG_ON(PageWriteback(page)); /* Writeback must be complete */ rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode); if (rc != MIGRATEPAGE_SUCCESS) return rc; migrate_page_copy(newpage, page); 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, bool offlining, 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); } /* * Only memory hotplug's offline_pages() caller has locked out KSM, * and can safely migrate a KSM page. The other cases have skipped * PageKsm along with PageReserved - but it is only now when we have * the page lock that we can be certain it will not go KSM beneath us * (KSM will not upgrade a page from PageAnon to PageKsm when it sees * its pagecount raised, but only here do we take the page lock which * serializes that). */ if (PageKsm(page) && !offlining) { rc = -EBUSY; goto unlock; } /* charge against new page */ mem_cgroup_prepare_migration(page, newpage, &mem); if (PageWriteback(page)) { /* * Only in the case of a full syncronous 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)) { /* * 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: 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, bool offlining, 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, offlining, 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, bool offlining, 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 * * The function takes one list of pages to migrate and a function * that determines from the page to be migrated and the private data * the target of the move and allocates the page. * * The function returns after 10 attempts or if no pages * are movable anymore because to has become empty * or no retryable pages exist anymore. * Caller should call putback_lru_pages to return pages to the LRU * or free list only if ret != 0. * * Return: Number of pages not migrated or error code. */ int migrate_pages(struct list_head *from, new_page_t get_new_page, unsigned long private, bool offlining, 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, offlining, 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, bool offlining, 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, offlining, 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) || PageKsm(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, 0, 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) || PageKsm(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, int 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_xchg_last_nid(newpage, page_last_nid(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 ret = 0; /* Avoid migrating to a node that is nearly full */ if (migrate_balanced_pgdat(pgdat, 1)) { int page_lru; if (isolate_lru_page(page)) { put_page(page); return 0; } /* Page is isolated */ ret = 1; page_lru = page_is_file_cache(page); if (!PageTransHuge(page)) inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru); else mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, HPAGE_PMD_NR); } /* * Page is either isolated or there is not enough space on the target * node. If isolated, then it has taken a reference count and the * callers reference can be safely dropped without the page * disappearing underneath us during migration. Otherwise the page is * not to be migrated but the callers reference should still be * dropped so it does not leak. */ put_page(page); return ret; } /* * 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 = 0; 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) { put_page(page); 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)) { put_page(page); 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, false, 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)); out: return isolated; } #endif /* CONFIG_NUMA_BALANCING */ #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) 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) { count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); goto out_dropref; } page_xchg_last_nid(new_page, page_last_nid(page)); isolated = numamigrate_isolate_page(pgdat, page); if (!isolated) { count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); put_page(new_page); goto out_keep_locked; } /* 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); 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_dropref: put_page(page); out_keep_locked: return 0; } #endif /* CONFIG_NUMA_BALANCING */ #endif /* CONFIG_NUMA */