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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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SPDX-License-Identifier: GPL-2.0/* * Memory Migration functionality - linux/mm/migrate.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/leafops.h>#include <linux/pagemap.h>#include <linux/buffer_head.h>#include <linux/mm_inline.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/backing-dev.h>#include <linux/compaction.h>#include <linux/syscalls.h>#include <linux/compat.h>#include <linux/hugetlb.h>#include <linux/gfp.h>#include <linux/page_idle.h>#include <linux/page_owner.h>#include <linux/sched/mm.h>#include <linux/ptrace.h>#include <linux/memory.h>#include <linux/sched/sysctl.h>#include <linux/memory-tiers.h>#include <linux/pagewalk.h>
#include <asm/tlbflush.h>
#include <trace/events/migrate.h>
#include "internal.h"#include "swap.h"
static const struct movable_operations *offline_movable_ops;static const struct movable_operations *zsmalloc_movable_ops;
int set_movable_ops(const struct movable_operations *ops, enum pagetype type){ /* * We only allow for selected types and don't handle concurrent * registration attempts yet. */ switch (type) { case PGTY_offline: if (offline_movable_ops && ops) return -EBUSY; offline_movable_ops = ops; break; case PGTY_zsmalloc: if (zsmalloc_movable_ops && ops) return -EBUSY; zsmalloc_movable_ops = ops; break; default: return -EINVAL; } return 0;}EXPORT_SYMBOL_GPL(set_movable_ops);
static const struct movable_operations *page_movable_ops(struct page *page){ VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page);
/* * If we enable page migration for a page of a certain type by marking * it as movable, the page type must be sticky until the page gets freed * back to the buddy. */ if (PageOffline(page)) /* Only balloon page migration sets PageOffline pages movable. */ return offline_movable_ops; if (PageZsmalloc(page)) return zsmalloc_movable_ops;
return NULL;}
/** * isolate_movable_ops_page - isolate a movable_ops page for migration * @page: The page. * @mode: The isolation mode. * * Try to isolate a movable_ops page for migration. Will fail if the page is * not a movable_ops page, if the page is already isolated for migration * or if the page was just was released by its owner. * * Once isolated, the page cannot get freed until it is either putback * or migrated. * * Returns true if isolation succeeded, otherwise false. */bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode){ /* * TODO: these pages will not be folios in the future. All * folio dependencies will have to be removed. */ struct folio *folio = folio_get_nontail_page(page); const struct movable_operations *mops;
/* * Avoid burning cycles with pages that are yet under __free_pages(), * or just got freed under us. * * In case we 'win' a race for a movable page being freed under us and * raise its refcount preventing __free_pages() from doing its job * the put_page() at the end of this block will take care of * release this page, thus avoiding a nasty leakage. */ if (!folio) goto out;
/* * Check for movable_ops pages before taking the page lock because * we use non-atomic bitops on newly allocated page flags so * unconditionally grabbing the lock ruins page's owner side. * * Note that once a page has movable_ops, it will stay that way * until the page was freed. */ if (unlikely(!page_has_movable_ops(page))) goto out_putfolio;
/* * As movable pages are not isolated from LRU lists, concurrent * compaction threads can race against page migration functions * as well as race against the releasing a page. * * In order to avoid having an already isolated movable page * being (wrongly) re-isolated while it is under migration, * or to avoid attempting to isolate pages being released, * lets be sure we have the page lock * before proceeding with the movable page isolation steps. */ if (unlikely(!folio_trylock(folio))) goto out_putfolio;
VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page); if (PageMovableOpsIsolated(page)) goto out_no_isolated;
mops = page_movable_ops(page); if (WARN_ON_ONCE(!mops)) goto out_no_isolated;
if (!mops->isolate_page(page, mode)) goto out_no_isolated;
/* Driver shouldn't use the isolated flag */ VM_WARN_ON_ONCE_PAGE(PageMovableOpsIsolated(page), page); SetPageMovableOpsIsolated(page); folio_unlock(folio);
return true;
out_no_isolated: folio_unlock(folio);out_putfolio: folio_put(folio);out: return false;}
/** * putback_movable_ops_page - putback an isolated movable_ops page * @page: The isolated page. * * Putback an isolated movable_ops page. * * After the page was putback, it might get freed instantly. */static void putback_movable_ops_page(struct page *page){ /* * TODO: these pages will not be folios in the future. All * folio dependencies will have to be removed. */ struct folio *folio = page_folio(page);
VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(page), page); VM_WARN_ON_ONCE_PAGE(!PageMovableOpsIsolated(page), page); folio_lock(folio); page_movable_ops(page)->putback_page(page); ClearPageMovableOpsIsolated(page); folio_unlock(folio); folio_put(folio);}
/** * migrate_movable_ops_page - migrate an isolated movable_ops page * @dst: The destination page. * @src: The source page. * @mode: The migration mode. * * Migrate an isolated movable_ops page. * * If the src page was already released by its owner, the src page is * un-isolated (putback) and migration succeeds; the migration core will be the * owner of both pages. * * If the src page was not released by its owner and the migration was * successful, the owner of the src page and the dst page are swapped and * the src page is un-isolated. * * If migration fails, the ownership stays unmodified and the src page * remains isolated: migration may be retried later or the page can be putback. * * TODO: migration core will treat both pages as folios and lock them before * this call to unlock them after this call. Further, the folio refcounts on * src and dst are also released by migration core. These pages will not be * folios in the future, so that must be reworked. * * Returns 0 on success, otherwise a negative error code. */static int migrate_movable_ops_page(struct page *dst, struct page *src, enum migrate_mode mode){ int rc;
VM_WARN_ON_ONCE_PAGE(!page_has_movable_ops(src), src); VM_WARN_ON_ONCE_PAGE(!PageMovableOpsIsolated(src), src); rc = page_movable_ops(src)->migrate_page(dst, src, mode); if (!rc) ClearPageMovableOpsIsolated(src); return rc;}
/* * Put previously isolated pages back onto the appropriate lists * from where they were once taken off for compaction/migration. * * This function shall be used whenever the isolated pageset has been * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range() * and folio_isolate_hugetlb(). */void putback_movable_pages(struct list_head *l){ struct folio *folio; struct folio *folio2;
list_for_each_entry_safe(folio, folio2, l, lru) { if (unlikely(folio_test_hugetlb(folio))) { folio_putback_hugetlb(folio); continue; } list_del(&folio->lru); if (unlikely(page_has_movable_ops(&folio->page))) { putback_movable_ops_page(&folio->page); } else { node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio), -folio_nr_pages(folio)); folio_putback_lru(folio); } }}
/* Must be called with an elevated refcount on the non-hugetlb folio */bool isolate_folio_to_list(struct folio *folio, struct list_head *list){ if (folio_test_hugetlb(folio)) return folio_isolate_hugetlb(folio, list);
if (page_has_movable_ops(&folio->page)) { if (!isolate_movable_ops_page(&folio->page, ISOLATE_UNEVICTABLE)) return false; } else { if (!folio_isolate_lru(folio)) return false; node_stat_add_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio)); } list_add(&folio->lru, list); return true;}
static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, struct folio *folio, pte_t old_pte, unsigned long idx){ struct page *page = folio_page(folio, idx); pte_t newpte;
if (PageCompound(page) || PageHWPoison(page)) return false;
VM_BUG_ON_PAGE(!PageAnon(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(pte_present(old_pte), page); VM_WARN_ON_ONCE_FOLIO(folio_is_device_private(folio), folio);
if (folio_test_mlocked(folio) || (pvmw->vma->vm_flags & VM_LOCKED) || mm_forbids_zeropage(pvmw->vma->vm_mm)) return false;
/* * The pmd entry mapping the old thp was flushed and the pte mapping * this subpage has been non present. If the subpage is only zero-filled * then map it to the shared zeropage. */ if (!pages_identical(page, ZERO_PAGE(0))) return false;
newpte = pte_mkspecial(pfn_pte(zero_pfn(pvmw->address), pvmw->vma->vm_page_prot));
if (pte_swp_soft_dirty(old_pte)) newpte = pte_mksoft_dirty(newpte); if (pte_swp_uffd_wp(old_pte)) newpte = pte_mkuffd_wp(newpte);
set_pte_at(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, newpte);
dec_mm_counter(pvmw->vma->vm_mm, mm_counter(folio)); return true;}
struct rmap_walk_arg { struct folio *folio; bool map_unused_to_zeropage;};
/* * Restore a potential migration pte to a working pte entry */static bool remove_migration_pte(struct folio *folio, struct vm_area_struct *vma, unsigned long addr, void *arg){ struct rmap_walk_arg *rmap_walk_arg = arg; DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION);
while (page_vma_mapped_walk(&pvmw)) { rmap_t rmap_flags = RMAP_NONE; pte_t old_pte; pte_t pte; softleaf_t entry; struct page *new; unsigned long idx = 0;
/* pgoff is invalid for ksm pages, but they are never large */ if (folio_test_large(folio) && !folio_test_hugetlb(folio)) idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff; new = folio_page(folio, idx);
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION /* PMD-mapped THP migration entry */ if (!pvmw.pte) { VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || !folio_test_pmd_mappable(folio), folio); remove_migration_pmd(&pvmw, new); continue; }#endif old_pte = ptep_get(pvmw.pte); if (rmap_walk_arg->map_unused_to_zeropage && try_to_map_unused_to_zeropage(&pvmw, folio, old_pte, idx)) continue;
folio_get(folio); pte = mk_pte(new, READ_ONCE(vma->vm_page_prot));
entry = softleaf_from_pte(old_pte); if (!softleaf_is_migration_young(entry)) pte = pte_mkold(pte); if (folio_test_dirty(folio) && softleaf_is_migration_dirty(entry)) pte = pte_mkdirty(pte); if (pte_swp_soft_dirty(old_pte)) pte = pte_mksoft_dirty(pte); else pte = pte_clear_soft_dirty(pte);
if (softleaf_is_migration_write(entry)) pte = pte_mkwrite(pte, vma); else if (pte_swp_uffd_wp(old_pte)) pte = pte_mkuffd_wp(pte);
if (folio_test_anon(folio) && !softleaf_is_migration_read(entry)) rmap_flags |= RMAP_EXCLUSIVE;
if (unlikely(is_device_private_page(new))) { if (pte_write(pte)) entry = make_writable_device_private_entry( page_to_pfn(new)); else entry = make_readable_device_private_entry( page_to_pfn(new)); pte = softleaf_to_pte(entry); if (pte_swp_soft_dirty(old_pte)) pte = pte_swp_mksoft_dirty(pte); if (pte_swp_uffd_wp(old_pte)) pte = pte_swp_mkuffd_wp(pte); }
#ifdef CONFIG_HUGETLB_PAGE if (folio_test_hugetlb(folio)) { struct hstate *h = hstate_vma(vma); unsigned int shift = huge_page_shift(h); unsigned long psize = huge_page_size(h);
pte = arch_make_huge_pte(pte, shift, vma->vm_flags); if (folio_test_anon(folio)) hugetlb_add_anon_rmap(folio, vma, pvmw.address, rmap_flags); else hugetlb_add_file_rmap(folio); set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte, psize); } else#endif { if (folio_test_anon(folio)) folio_add_anon_rmap_pte(folio, new, vma, pvmw.address, rmap_flags); else folio_add_file_rmap_pte(folio, new, vma); set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); } if (READ_ONCE(vma->vm_flags) & VM_LOCKED) mlock_drain_local();
trace_remove_migration_pte(pvmw.address, pte_val(pte), compound_order(new));
/* No need to invalidate - it was non-present before */ update_mmu_cache(vma, pvmw.address, pvmw.pte); }
return true;}
/* * Get rid of all migration entries and replace them by * references to the indicated page. */void remove_migration_ptes(struct folio *src, struct folio *dst, enum ttu_flags flags){ struct rmap_walk_arg rmap_walk_arg = { .folio = src, .map_unused_to_zeropage = flags & TTU_USE_SHARED_ZEROPAGE, };
struct rmap_walk_control rwc = { .rmap_one = remove_migration_pte, .arg = &rmap_walk_arg, };
VM_BUG_ON_FOLIO((flags & TTU_USE_SHARED_ZEROPAGE) && (src != dst), src);
if (flags & TTU_RMAP_LOCKED) rmap_walk_locked(dst, &rwc); else rmap_walk(dst, &rwc);}
/* * 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){ spinlock_t *ptl; pte_t *ptep; pte_t pte; softleaf_t entry;
ptep = pte_offset_map_lock(mm, pmd, address, &ptl); if (!ptep) return;
pte = ptep_get(ptep); pte_unmap(ptep);
if (pte_none(pte) || pte_present(pte)) goto out;
entry = softleaf_from_pte(pte); if (!softleaf_is_migration(entry)) goto out;
softleaf_entry_wait_on_locked(entry, ptl); return;out: spin_unlock(ptl);}
#ifdef CONFIG_HUGETLB_PAGE/* * The vma read lock must be held upon entry. Holding that lock prevents either * the pte or the ptl from being freed. * * This function will release the vma lock before returning. */void migration_entry_wait_huge(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep){ spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, ptep); softleaf_t entry; pte_t pte;
hugetlb_vma_assert_locked(vma); spin_lock(ptl); pte = huge_ptep_get(vma->vm_mm, addr, ptep);
if (huge_pte_none(pte)) goto fail;
entry = softleaf_from_pte(pte); if (softleaf_is_migration(entry)) { /* * If migration entry existed, safe to release vma lock * here because the pgtable page won't be freed without the * pgtable lock released. See comment right above pgtable * lock release in softleaf_entry_wait_on_locked(). */ hugetlb_vma_unlock_read(vma); softleaf_entry_wait_on_locked(entry, ptl); return; }
fail: spin_unlock(ptl); hugetlb_vma_unlock_read(vma);}#endif
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATIONvoid pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd){ spinlock_t *ptl;
ptl = pmd_lock(mm, pmd); if (!pmd_is_migration_entry(*pmd)) goto unlock; softleaf_entry_wait_on_locked(softleaf_from_pmd(*pmd), ptl); return;unlock: spin_unlock(ptl);}#endif
/* * Replace the folio in the mapping. * * The number of remaining references must be: * 1 for anonymous folios without a mapping * 2 for folios with a mapping * 3 for folios with a mapping and the private flag set. */static int __folio_migrate_mapping(struct address_space *mapping, struct folio *newfolio, struct folio *folio, int expected_count){ XA_STATE(xas, &mapping->i_pages, folio->index); struct swap_cluster_info *ci = NULL; struct zone *oldzone, *newzone; int dirty; long nr = folio_nr_pages(folio);
if (!mapping) { /* Take off deferred split queue while frozen and memcg set */ if (folio_test_large(folio) && folio_test_large_rmappable(folio)) { if (!folio_ref_freeze(folio, expected_count)) return -EAGAIN; folio_unqueue_deferred_split(folio); folio_ref_unfreeze(folio, expected_count); }
/* No turning back from here */ newfolio->index = folio->index; newfolio->mapping = folio->mapping; if (folio_test_anon(folio) && folio_test_large(folio)) mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); if (folio_test_swapbacked(folio)) __folio_set_swapbacked(newfolio);
return 0; }
oldzone = folio_zone(folio); newzone = folio_zone(newfolio);
if (folio_test_swapcache(folio)) ci = swap_cluster_get_and_lock_irq(folio); else xas_lock_irq(&xas);
if (!folio_ref_freeze(folio, expected_count)) { if (ci) swap_cluster_unlock_irq(ci); else xas_unlock_irq(&xas); return -EAGAIN; }
/* Take off deferred split queue while frozen and memcg set */ folio_unqueue_deferred_split(folio);
/* * Now we know that no one else is looking at the folio: * no turning back from here. */ newfolio->index = folio->index; newfolio->mapping = folio->mapping; if (folio_test_anon(folio) && folio_test_large(folio)) mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); folio_ref_add(newfolio, nr); /* add cache reference */ if (folio_test_swapbacked(folio)) __folio_set_swapbacked(newfolio); if (folio_test_swapcache(folio)) { folio_set_swapcache(newfolio); newfolio->private = folio_get_private(folio); }
/* Move dirty while folio refs frozen and newfolio not yet exposed */ dirty = folio_test_dirty(folio); if (dirty) { folio_clear_dirty(folio); folio_set_dirty(newfolio); }
if (folio_test_swapcache(folio)) __swap_cache_replace_folio(ci, folio, newfolio); else xas_store(&xas, newfolio);
/* * Drop cache reference from old folio by unfreezing * to one less reference. * We know this isn't the last reference. */ folio_ref_unfreeze(folio, expected_count - nr);
/* Leave irq disabled to prevent preemption while updating stats */ if (ci) swap_cluster_unlock(ci); else xas_unlock(&xas);
/* * If moved to a different zone then also account * the folio for that zone. Other VM counters will be * taken care of when we establish references to the * new folio and drop references to the old folio. * * Note that anonymous folios are accounted for * via NR_FILE_PAGES and NR_ANON_MAPPED if they * are mapped to swap space. */ if (newzone != oldzone) { struct lruvec *old_lruvec, *new_lruvec; struct mem_cgroup *memcg;
rcu_read_lock(); memcg = folio_memcg(folio); old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr); mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr); if (folio_test_swapbacked(folio) && !folio_test_swapcache(folio)) { mod_lruvec_state(old_lruvec, NR_SHMEM, -nr); mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
if (folio_test_pmd_mappable(folio)) { mod_lruvec_state(old_lruvec, NR_SHMEM_THPS, -nr); mod_lruvec_state(new_lruvec, NR_SHMEM_THPS, nr); } }#ifdef CONFIG_SWAP if (folio_test_swapcache(folio)) { mod_lruvec_state(old_lruvec, NR_SWAPCACHE, -nr); mod_lruvec_state(new_lruvec, NR_SWAPCACHE, nr); }#endif if (dirty && mapping_can_writeback(mapping)) { mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr); __mod_zone_page_state(oldzone, NR_ZONE_WRITE_PENDING, -nr); mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr); __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr); } rcu_read_unlock(); } local_irq_enable();
return 0;}
int folio_migrate_mapping(struct address_space *mapping, struct folio *newfolio, struct folio *folio, int extra_count){ int expected_count = folio_expected_ref_count(folio) + extra_count + 1;
if (folio_ref_count(folio) != expected_count) return -EAGAIN;
return __folio_migrate_mapping(mapping, newfolio, folio, expected_count);}EXPORT_SYMBOL(folio_migrate_mapping);
/* * The expected number of remaining references is the same as that * of folio_migrate_mapping(). */int migrate_huge_page_move_mapping(struct address_space *mapping, struct folio *dst, struct folio *src){ XA_STATE(xas, &mapping->i_pages, src->index); int rc, expected_count = folio_expected_ref_count(src) + 1;
if (folio_ref_count(src) != expected_count) return -EAGAIN;
rc = folio_mc_copy(dst, src); if (unlikely(rc)) return rc;
xas_lock_irq(&xas); if (!folio_ref_freeze(src, expected_count)) { xas_unlock_irq(&xas); return -EAGAIN; }
dst->index = src->index; dst->mapping = src->mapping;
folio_ref_add(dst, folio_nr_pages(dst));
xas_store(&xas, dst);
folio_ref_unfreeze(src, expected_count - folio_nr_pages(src));
xas_unlock_irq(&xas);
return 0;}
/* * Copy the flags and some other ancillary information */void folio_migrate_flags(struct folio *newfolio, struct folio *folio){ int cpupid;
if (folio_test_referenced(folio)) folio_set_referenced(newfolio); if (folio_test_uptodate(folio)) folio_mark_uptodate(newfolio); if (folio_test_clear_active(folio)) { VM_BUG_ON_FOLIO(folio_test_unevictable(folio), folio); folio_set_active(newfolio); } else if (folio_test_clear_unevictable(folio)) folio_set_unevictable(newfolio); if (folio_test_workingset(folio)) folio_set_workingset(newfolio); if (folio_test_checked(folio)) folio_set_checked(newfolio); /* * PG_anon_exclusive (-> PG_mappedtodisk) is always migrated via * migration entries. We can still have PG_anon_exclusive set on an * effectively unmapped and unreferenced first sub-pages of an * anonymous THP: we can simply copy it here via PG_mappedtodisk. */ if (folio_test_mappedtodisk(folio)) folio_set_mappedtodisk(newfolio);
/* Move dirty on pages not done by folio_migrate_mapping() */ if (folio_test_dirty(folio)) folio_set_dirty(newfolio);
if (folio_test_young(folio)) folio_set_young(newfolio); if (folio_test_idle(folio)) folio_set_idle(newfolio);
folio_migrate_refs(newfolio, folio); /* * Copy NUMA information to the new page, to prevent over-eager * future migrations of this same page. */ cpupid = folio_xchg_last_cpupid(folio, -1); /* * For memory tiering mode, when migrate between slow and fast * memory node, reset cpupid, because that is used to record * page access time in slow memory node. */ if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) { bool f_toptier = node_is_toptier(folio_nid(folio)); bool t_toptier = node_is_toptier(folio_nid(newfolio));
if (f_toptier != t_toptier) cpupid = -1; } folio_xchg_last_cpupid(newfolio, cpupid);
folio_migrate_ksm(newfolio, folio); /* * Please do not reorder this without considering how mm/ksm.c's * ksm_get_folio() depends upon ksm_migrate_page() and the * swapcache flag. */ if (folio_test_swapcache(folio)) folio_clear_swapcache(folio); folio_clear_private(folio);
/* page->private contains hugetlb specific flags */ if (!folio_test_hugetlb(folio)) folio->private = NULL;
/* * If any waiters have accumulated on the new page then * wake them up. */ if (folio_test_writeback(newfolio)) folio_end_writeback(newfolio);
/* * PG_readahead shares the same bit with PG_reclaim. The above * end_page_writeback() may clear PG_readahead mistakenly, so set the * bit after that. */ if (folio_test_readahead(folio)) folio_set_readahead(newfolio);
folio_copy_owner(newfolio, folio); pgalloc_tag_swap(newfolio, folio);
mem_cgroup_migrate(folio, newfolio);}EXPORT_SYMBOL(folio_migrate_flags);
/************************************************************ * Migration functions ***********************************************************/
static int __migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, void *src_private, enum migrate_mode mode){ int rc, expected_count = folio_expected_ref_count(src) + 1;
/* Check whether src does not have extra refs before we do more work */ if (folio_ref_count(src) != expected_count) return -EAGAIN;
rc = folio_mc_copy(dst, src); if (unlikely(rc)) return rc;
rc = __folio_migrate_mapping(mapping, dst, src, expected_count); if (rc) return rc;
if (src_private) folio_attach_private(dst, folio_detach_private(src));
folio_migrate_flags(dst, src); return 0;}
/** * migrate_folio() - Simple folio migration. * @mapping: The address_space containing the folio. * @dst: The folio to migrate the data to. * @src: The folio containing the current data. * @mode: How to migrate the page. * * Common logic to directly migrate a single LRU folio suitable for * folios that do not have private data. * * Folios are locked upon entry and exit. */int migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode){ BUG_ON(folio_test_writeback(src)); /* Writeback must be complete */ return __migrate_folio(mapping, dst, src, NULL, mode);}EXPORT_SYMBOL(migrate_folio);
#ifdef CONFIG_BUFFER_HEAD/* 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; struct buffer_head *failed_bh;
do { if (!trylock_buffer(bh)) { if (mode == MIGRATE_ASYNC) goto unlock; if (mode == MIGRATE_SYNC_LIGHT && !buffer_uptodate(bh)) goto unlock; lock_buffer(bh); }
bh = bh->b_this_page; } while (bh != head);
return true;
unlock: /* We failed to lock the buffer and cannot stall. */ failed_bh = bh; bh = head; while (bh != failed_bh) { unlock_buffer(bh); bh = bh->b_this_page; }
return false;}
static int __buffer_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode, bool check_refs){ struct buffer_head *bh, *head; int rc; int expected_count;
head = folio_buffers(src); if (!head) return migrate_folio(mapping, dst, src, mode);
/* Check whether page does not have extra refs before we do more work */ expected_count = folio_expected_ref_count(src) + 1; if (folio_ref_count(src) != expected_count) return -EAGAIN;
if (!buffer_migrate_lock_buffers(head, mode)) return -EAGAIN;
if (check_refs) { bool busy, migrating; bool invalidated = false;
migrating = test_and_set_bit_lock(BH_Migrate, &head->b_state); VM_WARN_ON_ONCE(migrating);recheck_buffers: busy = false; spin_lock(&mapping->i_private_lock); bh = head; do { if (atomic_read(&bh->b_count)) { busy = true; break; } bh = bh->b_this_page; } while (bh != head); spin_unlock(&mapping->i_private_lock); if (busy) { if (invalidated) { rc = -EAGAIN; goto unlock_buffers; } invalidate_bh_lrus(); invalidated = true; goto recheck_buffers; } }
rc = filemap_migrate_folio(mapping, dst, src, mode); if (rc) goto unlock_buffers;
bh = head; do { folio_set_bh(bh, dst, bh_offset(bh)); bh = bh->b_this_page; } while (bh != head);
unlock_buffers: if (check_refs) clear_bit_unlock(BH_Migrate, &head->b_state); bh = head; do { unlock_buffer(bh); bh = bh->b_this_page; } while (bh != head);
return rc;}
/** * buffer_migrate_folio() - Migration function for folios with buffers. * @mapping: The address space containing @src. * @dst: The folio to migrate to. * @src: The folio to migrate from. * @mode: How to migrate the folio. * * This function can only be used if the underlying filesystem guarantees * that no other references to @src exist. For example attached buffer * heads are accessed only under the folio lock. If your filesystem cannot * provide this guarantee, buffer_migrate_folio_norefs() may be more * appropriate. * * Return: 0 on success or a negative errno on failure. */int buffer_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode){ return __buffer_migrate_folio(mapping, dst, src, mode, false);}EXPORT_SYMBOL(buffer_migrate_folio);
/** * buffer_migrate_folio_norefs() - Migration function for folios with buffers. * @mapping: The address space containing @src. * @dst: The folio to migrate to. * @src: The folio to migrate from. * @mode: How to migrate the folio. * * Like buffer_migrate_folio() except that this variant is more careful * and checks that there are also no buffer head references. This function * is the right one for mappings where buffer heads are directly looked * up and referenced (such as block device mappings). * * Return: 0 on success or a negative errno on failure. */int buffer_migrate_folio_norefs(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode){ return __buffer_migrate_folio(mapping, dst, src, mode, true);}EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs);#endif /* CONFIG_BUFFER_HEAD */
int filemap_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode){ return __migrate_folio(mapping, dst, src, folio_get_private(src), mode);}EXPORT_SYMBOL_GPL(filemap_migrate_folio);
/* * Default handling if a filesystem does not provide a migration function. */static int fallback_migrate_folio(struct address_space *mapping, struct folio *dst, struct folio *src, enum migrate_mode mode){ WARN_ONCE(mapping->a_ops->writepages, "%ps does not implement migrate_folio\n", mapping->a_ops); if (folio_test_dirty(src)) return -EBUSY;
/* * Filesystem may have private data at folio->private that we * can't migrate automatically. */ if (!filemap_release_folio(src, GFP_KERNEL)) return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
return migrate_folio(mapping, dst, src, mode);}
/* * Move a src folio to a newly allocated dst folio. * * The src and dst folios are locked and the src folios was unmapped from * the page tables. * * On success, the src folio was replaced by the dst folio. * * Return value: * < 0 - error code * 0 - success */static int move_to_new_folio(struct folio *dst, struct folio *src, enum migrate_mode mode){ struct address_space *mapping = folio_mapping(src); int rc = -EAGAIN;
VM_BUG_ON_FOLIO(!folio_test_locked(src), src); VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
if (!mapping) rc = migrate_folio(mapping, dst, src, mode); else if (mapping_inaccessible(mapping)) rc = -EOPNOTSUPP; else if (mapping->a_ops->migrate_folio) /* * Most folios have a mapping and most filesystems * provide a migrate_folio callback. Anonymous folios * are part of swap space which also has its own * migrate_folio callback. This is the most common path * for page migration. */ rc = mapping->a_ops->migrate_folio(mapping, dst, src, mode); else rc = fallback_migrate_folio(mapping, dst, src, mode);
if (!rc) { /* * For pagecache folios, src->mapping must be cleared before src * is freed. Anonymous folios must stay anonymous until freed. */ if (!folio_test_anon(src)) src->mapping = NULL;
if (likely(!folio_is_zone_device(dst))) flush_dcache_folio(dst); } return rc;}
/* * To record some information during migration, we use unused private * field of struct folio of the newly allocated destination folio. * This is safe because nobody is using it except us. */enum { FOLIO_WAS_MAPPED = BIT(0), FOLIO_WAS_MLOCKED = BIT(1), FOLIO_OLD_STATES = FOLIO_WAS_MAPPED | FOLIO_WAS_MLOCKED,};
static void __migrate_folio_record(struct folio *dst, int old_folio_state, struct anon_vma *anon_vma){ dst->private = (void *)anon_vma + old_folio_state;}
static void __migrate_folio_extract(struct folio *dst, int *old_folio_state, struct anon_vma **anon_vmap){ unsigned long private = (unsigned long)dst->private;
*anon_vmap = (struct anon_vma *)(private & ~FOLIO_OLD_STATES); *old_folio_state = private & FOLIO_OLD_STATES; dst->private = NULL;}
/* Restore the source folio to the original state upon failure */static void migrate_folio_undo_src(struct folio *src, int page_was_mapped, struct anon_vma *anon_vma, bool locked, struct list_head *ret){ if (page_was_mapped) remove_migration_ptes(src, src, 0); /* Drop an anon_vma reference if we took one */ if (anon_vma) put_anon_vma(anon_vma); if (locked) folio_unlock(src); if (ret) list_move_tail(&src->lru, ret);}
/* Restore the destination folio to the original state upon failure */static void migrate_folio_undo_dst(struct folio *dst, bool locked, free_folio_t put_new_folio, unsigned long private){ if (locked) folio_unlock(dst); if (put_new_folio) put_new_folio(dst, private); else folio_put(dst);}
/* Cleanup src folio upon migration success */static void migrate_folio_done(struct folio *src, enum migrate_reason reason){ if (likely(!page_has_movable_ops(&src->page)) && reason != MR_DEMOTION) mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON + folio_is_file_lru(src), -folio_nr_pages(src));
if (reason != MR_MEMORY_FAILURE) /* We release the page in page_handle_poison. */ folio_put(src);}
/* Obtain the lock on page, remove all ptes. */static int migrate_folio_unmap(new_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, struct folio *src, struct folio **dstp, enum migrate_mode mode, struct list_head *ret){ struct folio *dst; int rc = -EAGAIN; int old_folio_state = 0; struct anon_vma *anon_vma = NULL; bool locked = false; bool dst_locked = false;
dst = get_new_folio(src, private); if (!dst) return -ENOMEM; *dstp = dst;
dst->private = NULL;
if (!folio_trylock(src)) { if (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_readahead). 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;
/* * In "light" mode, we can wait for transient locks (eg * inserting a page into the page table), but it's not * worth waiting for I/O. */ if (mode == MIGRATE_SYNC_LIGHT && !folio_test_uptodate(src)) goto out;
folio_lock(src); } locked = true; if (folio_test_mlocked(src)) old_folio_state |= FOLIO_WAS_MLOCKED;
if (folio_test_writeback(src)) { /* * Only in the case of a full synchronous migration is it * necessary to wait for writeback. In the async case, * the retry loop is too short and in the sync-light case, * the overhead of stalling is too much */ switch (mode) { case MIGRATE_SYNC: break; default: rc = -EBUSY; goto out; } folio_wait_writeback(src); }
/* * By try_to_migrate(), src->mapcount goes down to 0 here. In this case, * we cannot notice that anon_vma is freed while we migrate 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. * * Only folio_get_anon_vma() understands the subtleties of * getting a hold on an anon_vma from outside one of its mms. * But if we cannot get anon_vma, then we won't need it anyway, * because that implies that the anon page is no longer mapped * (and cannot be remapped so long as we hold the page lock). */ if (folio_test_anon(src) && !folio_test_ksm(src)) anon_vma = folio_get_anon_vma(src);
/* * Block others from accessing the new page when we get around to * establishing additional references. We are usually the only one * holding a reference to dst at this point. We used to have a BUG * here if folio_trylock(dst) fails, but would like to allow for * cases where there might be a race with the previous use of dst. * This is much like races on refcount of oldpage: just don't BUG(). */ if (unlikely(!folio_trylock(dst))) goto out; dst_locked = true;
if (unlikely(page_has_movable_ops(&src->page))) { __migrate_folio_record(dst, old_folio_state, anon_vma); return 0; }
/* * 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 src->mapping==NULL page will * trigger a BUG. So handle it here. * 2. An orphaned page (see truncate_cleanup_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 (!src->mapping) { if (folio_test_private(src)) { try_to_free_buffers(src); goto out; } } else if (folio_mapped(src)) { /* Establish migration ptes */ VM_BUG_ON_FOLIO(folio_test_anon(src) && !folio_test_ksm(src) && !anon_vma, src); try_to_migrate(src, mode == MIGRATE_ASYNC ? TTU_BATCH_FLUSH : 0); old_folio_state |= FOLIO_WAS_MAPPED; }
if (!folio_mapped(src)) { __migrate_folio_record(dst, old_folio_state, anon_vma); return 0; }
out: /* * A folio that has not been unmapped will be restored to * right list unless we want to retry. */ if (rc == -EAGAIN) ret = NULL;
migrate_folio_undo_src(src, old_folio_state & FOLIO_WAS_MAPPED, anon_vma, locked, ret); migrate_folio_undo_dst(dst, dst_locked, put_new_folio, private);
return rc;}
/* Migrate the folio to the newly allocated folio in dst. */static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, struct folio *src, struct folio *dst, enum migrate_mode mode, enum migrate_reason reason, struct list_head *ret){ int rc; int old_folio_state = 0; struct anon_vma *anon_vma = NULL; bool src_deferred_split = false; bool src_partially_mapped = false; struct list_head *prev;
__migrate_folio_extract(dst, &old_folio_state, &anon_vma); prev = dst->lru.prev; list_del(&dst->lru);
if (unlikely(page_has_movable_ops(&src->page))) { rc = migrate_movable_ops_page(&dst->page, &src->page, mode); if (rc) goto out; goto out_unlock_both; }
if (folio_order(src) > 1 && !data_race(list_empty(&src->_deferred_list))) { src_deferred_split = true; src_partially_mapped = folio_test_partially_mapped(src); }
rc = move_to_new_folio(dst, src, mode); if (rc) goto out;
/* * Requeue the destination folio on the deferred split queue if * the source was on the queue. The source is unqueued in * __folio_migrate_mapping(), so we recorded the state from * before move_to_new_folio(). */ if (src_deferred_split) deferred_split_folio(dst, src_partially_mapped);
/* * When successful, push dst to LRU immediately: so that if it * turns out to be an mlocked page, remove_migration_ptes() will * automatically build up the correct dst->mlock_count for it. * * We would like to do something similar for the old page, when * unsuccessful, and other cases when a page has been temporarily * isolated from the unevictable LRU: but this case is the easiest. */ folio_add_lru(dst); if (old_folio_state & FOLIO_WAS_MLOCKED) lru_add_drain();
if (old_folio_state & FOLIO_WAS_MAPPED) remove_migration_ptes(src, dst, 0);
out_unlock_both: folio_unlock(dst); folio_set_owner_migrate_reason(dst, reason); /* * If migration is successful, decrease refcount of dst, * which will not free the page because new page owner increased * refcounter. */ folio_put(dst);
/* * A folio that has been migrated has all references removed * and will be freed. */ list_del(&src->lru); /* Drop an anon_vma reference if we took one */ if (anon_vma) put_anon_vma(anon_vma); folio_unlock(src); migrate_folio_done(src, reason);
return rc;out: /* * A folio that has not been migrated will be restored to * right list unless we want to retry. */ if (rc == -EAGAIN) { list_add(&dst->lru, prev); __migrate_folio_record(dst, old_folio_state, anon_vma); return rc; }
migrate_folio_undo_src(src, old_folio_state & FOLIO_WAS_MAPPED, anon_vma, true, ret); migrate_folio_undo_dst(dst, true, put_new_folio, private);
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_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, struct folio *src, int force, enum migrate_mode mode, int reason, struct list_head *ret){ struct folio *dst; int rc = -EAGAIN; int page_was_mapped = 0; struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; enum ttu_flags ttu = 0;
if (folio_ref_count(src) == 1) { /* page was freed from under us. So we are done. */ folio_putback_hugetlb(src); return 0; }
dst = get_new_folio(src, private); if (!dst) return -ENOMEM;
if (!folio_trylock(src)) { if (!force) goto out; switch (mode) { case MIGRATE_SYNC: break; default: goto out; } folio_lock(src); }
/* * Check for pages which are in the process of being freed. Without * folio_mapping() set, hugetlbfs specific move page routine will not * be called and we could leak usage counts for subpools. */ if (hugetlb_folio_subpool(src) && !folio_mapping(src)) { rc = -EBUSY; goto out_unlock; }
if (folio_test_anon(src)) anon_vma = folio_get_anon_vma(src);
if (unlikely(!folio_trylock(dst))) goto put_anon;
if (folio_mapped(src)) { if (!folio_test_anon(src)) { /* * In shared mappings, try_to_unmap could potentially * call huge_pmd_unshare. Because of this, take * semaphore in write mode here and set TTU_RMAP_LOCKED * to let lower levels know we have taken the lock. */ mapping = hugetlb_folio_mapping_lock_write(src); if (unlikely(!mapping)) goto unlock_put_anon;
ttu = TTU_RMAP_LOCKED; }
try_to_migrate(src, ttu); page_was_mapped = 1; }
if (!folio_mapped(src)) rc = move_to_new_folio(dst, src, mode);
if (page_was_mapped) remove_migration_ptes(src, !rc ? dst : src, ttu);
if (ttu & TTU_RMAP_LOCKED) i_mmap_unlock_write(mapping);
unlock_put_anon: folio_unlock(dst);
put_anon: if (anon_vma) put_anon_vma(anon_vma);
if (!rc) { move_hugetlb_state(src, dst, reason); put_new_folio = NULL; }
out_unlock: folio_unlock(src);out: if (!rc) folio_putback_hugetlb(src); else if (rc != -EAGAIN) list_move_tail(&src->lru, ret);
/* * If migration was not successful and there's a freeing callback, * return the folio to that special allocator. Otherwise, simply drop * our additional reference. */ if (put_new_folio) put_new_folio(dst, private); else folio_put(dst);
return rc;}
static inline int try_split_folio(struct folio *folio, struct list_head *split_folios, enum migrate_mode mode){ int rc;
if (mode == MIGRATE_ASYNC) { if (!folio_trylock(folio)) return -EAGAIN; } else { folio_lock(folio); } rc = split_folio_to_list(folio, split_folios); folio_unlock(folio); if (!rc) list_move_tail(&folio->lru, split_folios);
return rc;}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE#define NR_MAX_BATCHED_MIGRATION HPAGE_PMD_NR#else#define NR_MAX_BATCHED_MIGRATION 512#endif#define NR_MAX_MIGRATE_PAGES_RETRY 10#define NR_MAX_MIGRATE_ASYNC_RETRY 3#define NR_MAX_MIGRATE_SYNC_RETRY \ (NR_MAX_MIGRATE_PAGES_RETRY - NR_MAX_MIGRATE_ASYNC_RETRY)
struct migrate_pages_stats { int nr_succeeded; /* Normal and large folios migrated successfully, in units of base pages */ int nr_failed_pages; /* Normal and large folios failed to be migrated, in units of base pages. Untried folios aren't counted */ int nr_thp_succeeded; /* THP migrated successfully */ int nr_thp_failed; /* THP failed to be migrated */ int nr_thp_split; /* THP split before migrating */ int nr_split; /* Large folio (include THP) split before migrating */};
/* * Returns the number of hugetlb folios that were not migrated, or an error code * after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no hugetlb folios are movable * any more because the list has become empty or no retryable hugetlb folios * exist any more. It is caller's responsibility to call putback_movable_pages() * only if ret != 0. */static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, enum migrate_mode mode, int reason, struct migrate_pages_stats *stats, struct list_head *ret_folios){ int retry = 1; int nr_failed = 0; int nr_retry_pages = 0; int pass = 0; struct folio *folio, *folio2; int rc, nr_pages;
for (pass = 0; pass < NR_MAX_MIGRATE_PAGES_RETRY && retry; pass++) { retry = 0; nr_retry_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) { if (!folio_test_hugetlb(folio)) continue;
nr_pages = folio_nr_pages(folio);
cond_resched();
/* * Migratability of hugepages depends on architectures and * their size. This check is necessary because some callers * of hugepage migration like soft offline and memory * hotremove don't walk through page tables or check whether * the hugepage is pmd-based or not before kicking migration. */ if (!hugepage_migration_supported(folio_hstate(folio))) { nr_failed++; stats->nr_failed_pages += nr_pages; list_move_tail(&folio->lru, ret_folios); continue; }
rc = unmap_and_move_huge_page(get_new_folio, put_new_folio, private, folio, pass > 2, mode, reason, ret_folios); /* * The rules are: * 0: hugetlb folio will be put back * -EAGAIN: stay on the from list * -ENOMEM: stay on the from list * Other errno: put on ret_folios list */ switch(rc) { case -ENOMEM: /* * When memory is low, don't bother to try to migrate * other folios, just exit. */ stats->nr_failed_pages += nr_pages + nr_retry_pages; return -ENOMEM; case -EAGAIN: retry++; nr_retry_pages += nr_pages; break; case 0: stats->nr_succeeded += nr_pages; break; default: /* * Permanent failure (-EBUSY, etc.): * unlike -EAGAIN case, the failed folio is * removed from migration folio list and not * retried in the next outer loop. */ nr_failed++; stats->nr_failed_pages += nr_pages; break; } } } /* * nr_failed is number of hugetlb folios failed to be migrated. After * NR_MAX_MIGRATE_PAGES_RETRY attempts, give up and count retried hugetlb * folios as failed. */ nr_failed += retry; stats->nr_failed_pages += nr_retry_pages;
return nr_failed;}
static void migrate_folios_move(struct list_head *src_folios, struct list_head *dst_folios, free_folio_t put_new_folio, unsigned long private, enum migrate_mode mode, int reason, struct list_head *ret_folios, struct migrate_pages_stats *stats, int *retry, int *thp_retry, int *nr_failed, int *nr_retry_pages){ struct folio *folio, *folio2, *dst, *dst2; bool is_thp; int nr_pages; int rc;
dst = list_first_entry(dst_folios, struct folio, lru); dst2 = list_next_entry(dst, lru); list_for_each_entry_safe(folio, folio2, src_folios, lru) { is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio); nr_pages = folio_nr_pages(folio);
cond_resched();
rc = migrate_folio_move(put_new_folio, private, folio, dst, mode, reason, ret_folios); /* * The rules are: * 0: folio will be freed * -EAGAIN: stay on the unmap_folios list * Other errno: put on ret_folios list */ switch (rc) { case -EAGAIN: *retry += 1; *thp_retry += is_thp; *nr_retry_pages += nr_pages; break; case 0: stats->nr_succeeded += nr_pages; stats->nr_thp_succeeded += is_thp; break; default: *nr_failed += 1; stats->nr_thp_failed += is_thp; stats->nr_failed_pages += nr_pages; break; } dst = dst2; dst2 = list_next_entry(dst, lru); }}
static void migrate_folios_undo(struct list_head *src_folios, struct list_head *dst_folios, free_folio_t put_new_folio, unsigned long private, struct list_head *ret_folios){ struct folio *folio, *folio2, *dst, *dst2;
dst = list_first_entry(dst_folios, struct folio, lru); dst2 = list_next_entry(dst, lru); list_for_each_entry_safe(folio, folio2, src_folios, lru) { int old_folio_state = 0; struct anon_vma *anon_vma = NULL;
__migrate_folio_extract(dst, &old_folio_state, &anon_vma); migrate_folio_undo_src(folio, old_folio_state & FOLIO_WAS_MAPPED, anon_vma, true, ret_folios); list_del(&dst->lru); migrate_folio_undo_dst(dst, true, put_new_folio, private); dst = dst2; dst2 = list_next_entry(dst, lru); }}
/* * migrate_pages_batch() first unmaps folios in the from list as many as * possible, then move the unmapped folios. * * We only batch migration if mode == MIGRATE_ASYNC to avoid to wait a * lock or bit when we have locked more than one folio. Which may cause * deadlock (e.g., for loop device). So, if mode != MIGRATE_ASYNC, the * length of the from list must be <= 1. */static int migrate_pages_batch(struct list_head *from, new_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, enum migrate_mode mode, int reason, struct list_head *ret_folios, struct list_head *split_folios, struct migrate_pages_stats *stats, int nr_pass){ int retry = 1; int thp_retry = 1; int nr_failed = 0; int nr_retry_pages = 0; int pass = 0; bool is_thp = false; bool is_large = false; struct folio *folio, *folio2, *dst = NULL; int rc, rc_saved = 0, nr_pages; LIST_HEAD(unmap_folios); LIST_HEAD(dst_folios); bool nosplit = (reason == MR_NUMA_MISPLACED);
VM_WARN_ON_ONCE(mode != MIGRATE_ASYNC && !list_empty(from) && !list_is_singular(from));
for (pass = 0; pass < nr_pass && retry; pass++) { retry = 0; thp_retry = 0; nr_retry_pages = 0;
list_for_each_entry_safe(folio, folio2, from, lru) { is_large = folio_test_large(folio); is_thp = folio_test_pmd_mappable(folio); nr_pages = folio_nr_pages(folio);
cond_resched();
/* * The rare folio on the deferred split list should * be split now. It should not count as a failure: * but increment nr_failed because, without doing so, * migrate_pages() may report success with (split but * unmigrated) pages still on its fromlist; whereas it * always reports success when its fromlist is empty. * stats->nr_thp_failed should be increased too, * otherwise stats inconsistency will happen when * migrate_pages_batch is called via migrate_pages() * with MIGRATE_SYNC and MIGRATE_ASYNC. * * Only check it without removing it from the list. * Since the folio can be on deferred_split_scan() * local list and removing it can cause the local list * corruption. Folio split process below can handle it * with the help of folio_ref_freeze(). * * nr_pages > 2 is needed to avoid checking order-1 * page cache folios. They exist, in contrast to * non-existent order-1 anonymous folios, and do not * use _deferred_list. */ if (nr_pages > 2 && !list_empty(&folio->_deferred_list) && folio_test_partially_mapped(folio)) { if (!try_split_folio(folio, split_folios, mode)) { nr_failed++; stats->nr_thp_failed += is_thp; stats->nr_thp_split += is_thp; stats->nr_split++; continue; } }
/* * Large folio migration might be unsupported or * the allocation might be failed so we should retry * on the same folio with the large folio split * to normal folios. * * Split folios are put in split_folios, and * we will migrate them after the rest of the * list is processed. */ if (!thp_migration_supported() && is_thp) { nr_failed++; stats->nr_thp_failed++; if (!try_split_folio(folio, split_folios, mode)) { stats->nr_thp_split++; stats->nr_split++; continue; } stats->nr_failed_pages += nr_pages; list_move_tail(&folio->lru, ret_folios); continue; }
/* * If we are holding the last folio reference, the folio * was freed from under us, so just drop our reference. */ if (likely(!page_has_movable_ops(&folio->page)) && folio_ref_count(folio) == 1) { folio_clear_active(folio); folio_clear_unevictable(folio); list_del(&folio->lru); migrate_folio_done(folio, reason); stats->nr_succeeded += nr_pages; stats->nr_thp_succeeded += is_thp; continue; }
rc = migrate_folio_unmap(get_new_folio, put_new_folio, private, folio, &dst, mode, ret_folios); /* * The rules are: * 0: folio will be put on unmap_folios list, * dst folio put on dst_folios list * -EAGAIN: stay on the from list * -ENOMEM: stay on the from list * Other errno: put on ret_folios list */ switch(rc) { case -ENOMEM: /* * When memory is low, don't bother to try to migrate * other folios, move unmapped folios, then exit. */ nr_failed++; stats->nr_thp_failed += is_thp; /* Large folio NUMA faulting doesn't split to retry. */ if (is_large && !nosplit) { int ret = try_split_folio(folio, split_folios, mode);
if (!ret) { stats->nr_thp_split += is_thp; stats->nr_split++; break; } else if (reason == MR_LONGTERM_PIN && ret == -EAGAIN) { /* * Try again to split large folio to * mitigate the failure of longterm pinning. */ retry++; thp_retry += is_thp; nr_retry_pages += nr_pages; /* Undo duplicated failure counting. */ nr_failed--; stats->nr_thp_failed -= is_thp; break; } }
stats->nr_failed_pages += nr_pages + nr_retry_pages; /* nr_failed isn't updated for not used */ stats->nr_thp_failed += thp_retry; rc_saved = rc; if (list_empty(&unmap_folios)) goto out; else goto move; case -EAGAIN: retry++; thp_retry += is_thp; nr_retry_pages += nr_pages; break; case 0: list_move_tail(&folio->lru, &unmap_folios); list_add_tail(&dst->lru, &dst_folios); break; default: /* * Permanent failure (-EBUSY, etc.): * unlike -EAGAIN case, the failed folio is * removed from migration folio list and not * retried in the next outer loop. */ nr_failed++; stats->nr_thp_failed += is_thp; stats->nr_failed_pages += nr_pages; break; } } } nr_failed += retry; stats->nr_thp_failed += thp_retry; stats->nr_failed_pages += nr_retry_pages;move: /* Flush TLBs for all unmapped folios */ try_to_unmap_flush();
retry = 1; for (pass = 0; pass < nr_pass && retry; pass++) { retry = 0; thp_retry = 0; nr_retry_pages = 0;
/* Move the unmapped folios */ migrate_folios_move(&unmap_folios, &dst_folios, put_new_folio, private, mode, reason, ret_folios, stats, &retry, &thp_retry, &nr_failed, &nr_retry_pages); } nr_failed += retry; stats->nr_thp_failed += thp_retry; stats->nr_failed_pages += nr_retry_pages;
rc = rc_saved ? : nr_failed;out: /* Cleanup remaining folios */ migrate_folios_undo(&unmap_folios, &dst_folios, put_new_folio, private, ret_folios);
return rc;}
static int migrate_pages_sync(struct list_head *from, new_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, enum migrate_mode mode, int reason, struct list_head *ret_folios, struct list_head *split_folios, struct migrate_pages_stats *stats){ int rc, nr_failed = 0; LIST_HEAD(folios); struct migrate_pages_stats astats;
memset(&astats, 0, sizeof(astats)); /* Try to migrate in batch with MIGRATE_ASYNC mode firstly */ rc = migrate_pages_batch(from, get_new_folio, put_new_folio, private, MIGRATE_ASYNC, reason, &folios, split_folios, &astats, NR_MAX_MIGRATE_ASYNC_RETRY); stats->nr_succeeded += astats.nr_succeeded; stats->nr_thp_succeeded += astats.nr_thp_succeeded; stats->nr_thp_split += astats.nr_thp_split; stats->nr_split += astats.nr_split; if (rc < 0) { stats->nr_failed_pages += astats.nr_failed_pages; stats->nr_thp_failed += astats.nr_thp_failed; list_splice_tail(&folios, ret_folios); return rc; } stats->nr_thp_failed += astats.nr_thp_split; /* * Do not count rc, as pages will be retried below. * Count nr_split only, since it includes nr_thp_split. */ nr_failed += astats.nr_split; /* * Fall back to migrate all failed folios one by one synchronously. All * failed folios except split THPs will be retried, so their failure * isn't counted */ list_splice_tail_init(&folios, from); while (!list_empty(from)) { list_move(from->next, &folios); rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio, private, mode, reason, ret_folios, split_folios, stats, NR_MAX_MIGRATE_SYNC_RETRY); list_splice_tail_init(&folios, ret_folios); if (rc < 0) return rc; nr_failed += rc; }
return nr_failed;}
/* * migrate_pages - migrate the folios specified in a list, to the free folios * supplied as the target for the page migration * * @from: The list of folios to be migrated. * @get_new_folio: The function used to allocate free folios to be used * as the target of the folio migration. * @put_new_folio: The function used to free target folios if migration * fails, or NULL if no special handling is necessary. * @private: Private data to be passed on to get_new_folio() * @mode: The migration mode that specifies the constraints for * folio migration, if any. * @reason: The reason for folio migration. * @ret_succeeded: Set to the number of folios migrated successfully if * the caller passes a non-NULL pointer. * * The function returns after NR_MAX_MIGRATE_PAGES_RETRY attempts or if no folios * are movable any more because the list has become empty or no retryable folios * exist any more. It is caller's responsibility to call putback_movable_pages() * only if ret != 0. * * Returns the number of {normal folio, large folio, hugetlb} that were not * migrated, or an error code. The number of large folio splits will be * considered as the number of non-migrated large folio, no matter how many * split folios of the large folio are migrated successfully. */int migrate_pages(struct list_head *from, new_folio_t get_new_folio, free_folio_t put_new_folio, unsigned long private, enum migrate_mode mode, int reason, unsigned int *ret_succeeded){ int rc, rc_gather; int nr_pages; struct folio *folio, *folio2; LIST_HEAD(folios); LIST_HEAD(ret_folios); LIST_HEAD(split_folios); struct migrate_pages_stats stats;
trace_mm_migrate_pages_start(mode, reason);
memset(&stats, 0, sizeof(stats));
rc_gather = migrate_hugetlbs(from, get_new_folio, put_new_folio, private, mode, reason, &stats, &ret_folios); if (rc_gather < 0) goto out;
again: nr_pages = 0; list_for_each_entry_safe(folio, folio2, from, lru) { /* Retried hugetlb folios will be kept in list */ if (folio_test_hugetlb(folio)) { list_move_tail(&folio->lru, &ret_folios); continue; }
nr_pages += folio_nr_pages(folio); if (nr_pages >= NR_MAX_BATCHED_MIGRATION) break; } if (nr_pages >= NR_MAX_BATCHED_MIGRATION) list_cut_before(&folios, from, &folio2->lru); else list_splice_init(from, &folios); if (mode == MIGRATE_ASYNC) rc = migrate_pages_batch(&folios, get_new_folio, put_new_folio, private, mode, reason, &ret_folios, &split_folios, &stats, NR_MAX_MIGRATE_PAGES_RETRY); else rc = migrate_pages_sync(&folios, get_new_folio, put_new_folio, private, mode, reason, &ret_folios, &split_folios, &stats); list_splice_tail_init(&folios, &ret_folios); if (rc < 0) { rc_gather = rc; list_splice_tail(&split_folios, &ret_folios); goto out; } if (!list_empty(&split_folios)) { /* * Failure isn't counted since all split folios of a large folio * is counted as 1 failure already. And, we only try to migrate * with minimal effort, force MIGRATE_ASYNC mode and retry once. */ migrate_pages_batch(&split_folios, get_new_folio, put_new_folio, private, MIGRATE_ASYNC, reason, &ret_folios, NULL, &stats, 1); list_splice_tail_init(&split_folios, &ret_folios); } rc_gather += rc; if (!list_empty(from)) goto again;out: /* * Put the permanent failure folio back to migration list, they * will be put back to the right list by the caller. */ list_splice(&ret_folios, from);
/* * Return 0 in case all split folios of fail-to-migrate large folios * are migrated successfully. */ if (list_empty(from)) rc_gather = 0;
count_vm_events(PGMIGRATE_SUCCESS, stats.nr_succeeded); count_vm_events(PGMIGRATE_FAIL, stats.nr_failed_pages); count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded); count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed); count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split); trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages, stats.nr_thp_succeeded, stats.nr_thp_failed, stats.nr_thp_split, stats.nr_split, mode, reason);
if (ret_succeeded) *ret_succeeded = stats.nr_succeeded;
return rc_gather;}
struct folio *alloc_migration_target(struct folio *src, unsigned long private){ struct migration_target_control *mtc; gfp_t gfp_mask; unsigned int order = 0; int nid; enum zone_type zidx;
mtc = (struct migration_target_control *)private; gfp_mask = mtc->gfp_mask; nid = mtc->nid; if (nid == NUMA_NO_NODE) nid = folio_nid(src);
if (folio_test_hugetlb(src)) { struct hstate *h = folio_hstate(src);
gfp_mask = htlb_modify_alloc_mask(h, gfp_mask); return alloc_hugetlb_folio_nodemask(h, nid, mtc->nmask, gfp_mask, htlb_allow_alloc_fallback(mtc->reason)); }
if (folio_test_large(src)) { /* * clear __GFP_RECLAIM to make the migration callback * consistent with regular THP allocations. */ gfp_mask &= ~__GFP_RECLAIM; gfp_mask |= GFP_TRANSHUGE; order = folio_order(src); } zidx = folio_zonenum(src); if (is_highmem_idx(zidx) || zidx == ZONE_MOVABLE) gfp_mask |= __GFP_HIGHMEM;
return __folio_alloc(gfp_mask, order, nid, mtc->nmask);}
#ifdef CONFIG_NUMA_MIGRATIONstatic int store_status(int __user *status, int start, int value, int nr){ while (nr-- > 0) { if (put_user(value, status + start)) return -EFAULT; start++; }
return 0;}
static int do_move_pages_to_node(struct list_head *pagelist, int node){ int err; struct migration_target_control mtc = { .nid = node, .gfp_mask = GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, .reason = MR_SYSCALL, };
err = migrate_pages(pagelist, alloc_migration_target, NULL, (unsigned long)&mtc, MIGRATE_SYNC, MR_SYSCALL, NULL); if (err) putback_movable_pages(pagelist); return err;}
static int __add_folio_for_migration(struct folio *folio, int node, struct list_head *pagelist, bool migrate_all){ if (is_zero_folio(folio) || is_huge_zero_folio(folio)) return -EFAULT;
if (folio_is_zone_device(folio)) return -ENOENT;
if (folio_nid(folio) == node) return 0;
if (folio_maybe_mapped_shared(folio) && !migrate_all) return -EACCES;
if (folio_test_hugetlb(folio)) { if (folio_isolate_hugetlb(folio, pagelist)) return 1; } else if (folio_isolate_lru(folio)) { list_add_tail(&folio->lru, pagelist); node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio), folio_nr_pages(folio)); return 1; } return -EBUSY;}
/* * Resolves the given address to a struct folio, isolates it from the LRU and * puts it to the given pagelist. * Returns: * errno - if the folio cannot be found/isolated * 0 - when it doesn't have to be migrated because it is already on the * target node * 1 - when it has been queued */static int add_folio_for_migration(struct mm_struct *mm, const void __user *p, int node, struct list_head *pagelist, bool migrate_all){ struct vm_area_struct *vma; struct folio_walk fw; struct folio *folio; unsigned long addr; int err = -EFAULT;
mmap_read_lock(mm); addr = (unsigned long)untagged_addr_remote(mm, p);
vma = vma_lookup(mm, addr); if (vma && vma_migratable(vma)) { folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE); if (folio) { err = __add_folio_for_migration(folio, node, pagelist, migrate_all); folio_walk_end(&fw, vma); } else { err = -ENOENT; } } mmap_read_unlock(mm); return err;}
static int move_pages_and_store_status(int node, struct list_head *pagelist, int __user *status, int start, int i, unsigned long nr_pages){ int err;
if (list_empty(pagelist)) return 0;
err = do_move_pages_to_node(pagelist, node); if (err) { /* * Positive err means the number of failed * pages to migrate. Since we are going to * abort and return the number of non-migrated * pages, so need to include the rest of the * nr_pages that have not been attempted as * well. */ if (err > 0) err += nr_pages - i; return err; } return store_status(status, start, node, i - start);}
/* * 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){ compat_uptr_t __user *compat_pages = (void __user *)pages; int current_node = NUMA_NO_NODE; LIST_HEAD(pagelist); int start, i; int err = 0, err1;
lru_cache_disable();
for (i = start = 0; i < nr_pages; i++) { const void __user *p; int node;
err = -EFAULT; if (in_compat_syscall()) { compat_uptr_t cp;
if (get_user(cp, compat_pages + i)) goto out_flush;
p = compat_ptr(cp); } else { if (get_user(p, pages + i)) goto out_flush; } if (get_user(node, nodes + i)) goto out_flush;
err = -ENODEV; if (node < 0 || node >= MAX_NUMNODES) goto out_flush; if (!node_state(node, N_MEMORY)) goto out_flush;
err = -EACCES; if (!node_isset(node, task_nodes)) goto out_flush;
if (current_node == NUMA_NO_NODE) { current_node = node; start = i; } else if (node != current_node) { err = move_pages_and_store_status(current_node, &pagelist, status, start, i, nr_pages); if (err) goto out; start = i; current_node = node; }
/* * Errors in the page lookup or isolation are not fatal and we simply * report them via status */ err = add_folio_for_migration(mm, p, current_node, &pagelist, flags & MPOL_MF_MOVE_ALL);
if (err > 0) { /* The page is successfully queued for migration */ continue; }
/* * If the page is already on the target node (!err), store the * node, otherwise, store the err. */ err = store_status(status, i, err ? : current_node, 1); if (err) goto out_flush;
err = move_pages_and_store_status(current_node, &pagelist, status, start, i, nr_pages); if (err) { /* We have accounted for page i */ if (err > 0) err--; goto out; } current_node = NUMA_NO_NODE; }out_flush: /* Make sure we do not overwrite the existing error */ err1 = move_pages_and_store_status(current_node, &pagelist, status, start, i, nr_pages); if (err >= 0) err = err1;out: lru_cache_enable(); 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;
mmap_read_lock(mm);
for (i = 0; i < nr_pages; i++) { unsigned long addr = (unsigned long)(*pages); struct vm_area_struct *vma; struct folio_walk fw; struct folio *folio; int err = -EFAULT;
vma = vma_lookup(mm, addr); if (!vma) goto set_status;
folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE); if (folio) { if (is_zero_folio(folio) || is_huge_zero_folio(folio)) err = -EFAULT; else if (folio_is_zone_device(folio)) err = -ENOENT; else err = folio_nid(folio); folio_walk_end(&fw, vma); } else { err = -ENOENT; }set_status: *status = err;
pages++; status++; }
mmap_read_unlock(mm);}
static int get_compat_pages_array(const void __user *chunk_pages[], const void __user * __user *pages, unsigned long chunk_offset, unsigned long chunk_nr){ compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; compat_uptr_t p; int i;
for (i = 0; i < chunk_nr; i++) { if (get_user(p, pages32 + chunk_offset + i)) return -EFAULT; chunk_pages[i] = compat_ptr(p); }
return 0;}
/* * 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 16UL const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; int chunk_status[DO_PAGES_STAT_CHUNK_NR]; unsigned long chunk_offset = 0;
while (nr_pages) { unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR);
if (in_compat_syscall()) { if (get_compat_pages_array(chunk_pages, pages, chunk_offset, chunk_nr)) break; } else { if (copy_from_user(chunk_pages, pages + chunk_offset, chunk_nr * sizeof(*chunk_pages))) break; }
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
if (copy_to_user(status + chunk_offset, chunk_status, chunk_nr * sizeof(*status))) break;
chunk_offset += chunk_nr; nr_pages -= chunk_nr; } return nr_pages ? -EFAULT : 0;}
static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes){ struct task_struct *task; struct mm_struct *mm;
/* * There is no need to check if current process has the right to modify * the specified process when they are same. */ if (!pid) { mmget(current->mm); *mem_nodes = cpuset_mems_allowed(current); return current->mm; }
task = find_get_task_by_vpid(pid); if (!task) return ERR_PTR(-ESRCH);
if (down_read_killable(&task->signal->exec_update_lock)) { mm = ERR_PTR(-EINTR); goto out; } /* * Check if this process has the right to modify the specified * process. Use the regular "ptrace_may_access()" checks. */ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { mm = ERR_PTR(-EPERM); goto unlock; }
mm = ERR_PTR(security_task_movememory(task)); if (IS_ERR(mm)) goto unlock; *mem_nodes = cpuset_mems_allowed(task); mm = get_task_mm(task);unlock: up_read(&task->signal->exec_update_lock);out: put_task_struct(task); if (!mm) mm = ERR_PTR(-EINVAL); return mm;}
/* * Move a list of pages in the address space of the currently executing * process. */static int kernel_move_pages(pid_t pid, unsigned long nr_pages, const void __user * __user *pages, const int __user *nodes, int __user *status, int flags){ 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;
mm = find_mm_struct(pid, &task_nodes); if (IS_ERR(mm)) return PTR_ERR(mm);
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;}
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){ return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);}#endif /* CONFIG_NUMA_MIGRATION */
#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 is 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 (!managed_zone(zone)) continue;
/* Avoid waking kswapd by allocating pages_to_migrate pages. */ if (!zone_watermark_ok(zone, 0, high_wmark_pages(zone) + nr_migrate_pages, ZONE_MOVABLE, ALLOC_CMA)) continue; return true; } return false;}
static struct folio *alloc_misplaced_dst_folio(struct folio *src, unsigned long data){ int nid = (int) data; int order = folio_order(src); gfp_t gfp = __GFP_THISNODE;
if (order > 0) gfp |= GFP_TRANSHUGE_LIGHT; else { gfp |= GFP_HIGHUSER_MOVABLE | __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN; gfp &= ~__GFP_RECLAIM; } return __folio_alloc_node(gfp, order, nid);}
/* * Prepare for calling migrate_misplaced_folio() by isolating the folio if * permitted. Must be called with the PTL still held. */int migrate_misplaced_folio_prepare(struct folio *folio, struct vm_area_struct *vma, int node){ int nr_pages = folio_nr_pages(folio); pg_data_t *pgdat = NODE_DATA(node);
if (folio_is_file_lru(folio)) { /* * Do not migrate file folios that are mapped in multiple * processes with execute permissions as they are probably * shared libraries. * * See folio_maybe_mapped_shared() on possible imprecision * when we cannot easily detect if a folio is shared. */ if ((vma->vm_flags & VM_EXEC) && folio_maybe_mapped_shared(folio)) return -EACCES;
/* * Do not migrate dirty folios as not all filesystems can move * dirty folios in MIGRATE_ASYNC mode which is a waste of * cycles. */ if (folio_test_dirty(folio)) return -EAGAIN; }
/* Avoid migrating to a node that is nearly full */ if (!migrate_balanced_pgdat(pgdat, nr_pages)) { int z;
if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)) return -EAGAIN; for (z = pgdat->nr_zones - 1; z >= 0; z--) { if (managed_zone(pgdat->node_zones + z)) break; }
/* * If there are no managed zones, it should not proceed * further. */ if (z < 0) return -EAGAIN;
wakeup_kswapd(pgdat->node_zones + z, 0, folio_order(folio), ZONE_MOVABLE); return -EAGAIN; }
if (!folio_isolate_lru(folio)) return -EAGAIN;
node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio), nr_pages); return 0;}
/* * Attempt to migrate a misplaced folio to the specified destination * node. Caller is expected to have isolated the folio by calling * migrate_misplaced_folio_prepare(), which will result in an * elevated reference count on the folio. This function will un-isolate the * folio, dereferencing the folio before returning. */int migrate_misplaced_folio(struct folio *folio, int node){ pg_data_t *pgdat = NODE_DATA(node); int nr_remaining; unsigned int nr_succeeded; LIST_HEAD(migratepages); struct mem_cgroup *memcg = get_mem_cgroup_from_folio(folio); struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
list_add(&folio->lru, &migratepages); nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_folio, NULL, node, MIGRATE_ASYNC, MR_NUMA_MISPLACED, &nr_succeeded); if (nr_remaining && !list_empty(&migratepages)) putback_movable_pages(&migratepages); if (nr_succeeded) { count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded); count_memcg_events(memcg, NUMA_PAGE_MIGRATE, nr_succeeded); if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && !node_is_toptier(folio_nid(folio)) && node_is_toptier(node)) mod_lruvec_state(lruvec, PGPROMOTE_SUCCESS, nr_succeeded); } mem_cgroup_put(memcg); BUG_ON(!list_empty(&migratepages)); return nr_remaining ? -EAGAIN : 0;}#endif /* CONFIG_NUMA_BALANCING */