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-rw-r--r--mm/khugepaged.c154
1 files changed, 103 insertions, 51 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4734315f7940..5a7d2d5093f9 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -97,8 +97,8 @@ struct collapse_control {
/* Num pages scanned per node */
u32 node_load[MAX_NUMNODES];
- /* Last target selected in hpage_collapse_find_target_node() */
- int last_target_node;
+ /* nodemask for allocation fallback */
+ nodemask_t alloc_nmask;
};
/**
@@ -734,7 +734,6 @@ static void khugepaged_alloc_sleep(void)
struct collapse_control khugepaged_collapse_control = {
.is_khugepaged = true,
- .last_target_node = NUMA_NO_NODE,
};
static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc)
@@ -783,16 +782,11 @@ static int hpage_collapse_find_target_node(struct collapse_control *cc)
target_node = nid;
}
- /* do some balance if several nodes have the same hit record */
- if (target_node <= cc->last_target_node)
- for (nid = cc->last_target_node + 1; nid < MAX_NUMNODES;
- nid++)
- if (max_value == cc->node_load[nid]) {
- target_node = nid;
- break;
- }
+ for_each_online_node(nid) {
+ if (max_value == cc->node_load[nid])
+ node_set(nid, cc->alloc_nmask);
+ }
- cc->last_target_node = target_node;
return target_node;
}
#else
@@ -802,9 +796,10 @@ static int hpage_collapse_find_target_node(struct collapse_control *cc)
}
#endif
-static bool hpage_collapse_alloc_page(struct page **hpage, gfp_t gfp, int node)
+static bool hpage_collapse_alloc_page(struct page **hpage, gfp_t gfp, int node,
+ nodemask_t *nmask)
{
- *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
+ *hpage = __alloc_pages(gfp, HPAGE_PMD_ORDER, node, nmask);
if (unlikely(!*hpage)) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
return false;
@@ -955,12 +950,11 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
struct collapse_control *cc)
{
- /* Only allocate from the target node */
gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
- GFP_TRANSHUGE) | __GFP_THISNODE;
+ GFP_TRANSHUGE);
int node = hpage_collapse_find_target_node(cc);
- if (!hpage_collapse_alloc_page(hpage, gfp, node))
+ if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask))
return SCAN_ALLOC_HUGE_PAGE_FAIL;
if (unlikely(mem_cgroup_charge(page_folio(*hpage), mm, gfp)))
return SCAN_CGROUP_CHARGE_FAIL;
@@ -1057,6 +1051,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(&range);
+ tlb_remove_table_sync_one();
spin_lock(pte_ptl);
result = __collapse_huge_page_isolate(vma, address, pte, cc,
@@ -1144,6 +1139,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
goto out;
memset(cc->node_load, 0, sizeof(cc->node_load));
+ nodes_clear(cc->alloc_nmask);
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, _address += PAGE_SIZE) {
@@ -1242,15 +1238,8 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
/*
* Check if the page has any GUP (or other external) pins.
*
- * Here the check is racy it may see total_mapcount > refcount
- * in some cases.
- * For example, one process with one forked child process.
- * The parent has the PMD split due to MADV_DONTNEED, then
- * the child is trying unmap the whole PMD, but khugepaged
- * may be scanning the parent between the child has
- * PageDoubleMap flag cleared and dec the mapcount. So
- * khugepaged may see total_mapcount > refcount.
- *
+ * Here the check may be racy:
+ * it may see total_mapcount > refcount in some cases?
* But such case is ephemeral we could always retry collapse
* later. However it may report false positive if the page
* has excessive GUP pins (i.e. 512). Anyway the same check
@@ -1384,16 +1373,43 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
return SCAN_SUCCEED;
}
+/*
+ * A note about locking:
+ * Trying to take the page table spinlocks would be useless here because those
+ * are only used to synchronize:
+ *
+ * - modifying terminal entries (ones that point to a data page, not to another
+ * page table)
+ * - installing *new* non-terminal entries
+ *
+ * Instead, we need roughly the same kind of protection as free_pgtables() or
+ * mm_take_all_locks() (but only for a single VMA):
+ * The mmap lock together with this VMA's rmap locks covers all paths towards
+ * the page table entries we're messing with here, except for hardware page
+ * table walks and lockless_pages_from_mm().
+ */
static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)
{
- spinlock_t *ptl;
pmd_t pmd;
+ struct mmu_notifier_range range;
mmap_assert_write_locked(mm);
- ptl = pmd_lock(vma->vm_mm, pmdp);
+ if (vma->vm_file)
+ lockdep_assert_held_write(&vma->vm_file->f_mapping->i_mmap_rwsem);
+ /*
+ * All anon_vmas attached to the VMA have the same root and are
+ * therefore locked by the same lock.
+ */
+ if (vma->anon_vma)
+ lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, addr,
+ addr + HPAGE_PMD_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
pmd = pmdp_collapse_flush(vma, addr, pmdp);
- spin_unlock(ptl);
+ tlb_remove_table_sync_one();
+ mmu_notifier_invalidate_range_end(&range);
mm_dec_nr_ptes(mm);
page_table_check_pte_clear_range(mm, addr, pmd);
pte_free(mm, pmd_pgtable(pmd));
@@ -1444,6 +1460,14 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
return SCAN_VMA_CHECK;
+ /*
+ * Symmetry with retract_page_tables(): Exclude MAP_PRIVATE mappings
+ * that got written to. Without this, we'd have to also lock the
+ * anon_vma if one exists.
+ */
+ if (vma->anon_vma)
+ return SCAN_VMA_CHECK;
+
/* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
if (userfaultfd_wp(vma))
return SCAN_PTE_UFFD_WP;
@@ -1477,6 +1501,20 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
goto drop_hpage;
}
+ /*
+ * We need to lock the mapping so that from here on, only GUP-fast and
+ * hardware page walks can access the parts of the page tables that
+ * we're operating on.
+ * See collapse_and_free_pmd().
+ */
+ i_mmap_lock_write(vma->vm_file->f_mapping);
+
+ /*
+ * This spinlock should be unnecessary: Nobody else should be accessing
+ * the page tables under spinlock protection here, only
+ * lockless_pages_from_mm() and the hardware page walker can access page
+ * tables while all the high-level locks are held in write mode.
+ */
start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
result = SCAN_FAIL;
@@ -1531,6 +1569,8 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
/* step 4: remove pte entries */
collapse_and_free_pmd(mm, vma, haddr, pmd);
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+
maybe_install_pmd:
/* step 5: install pmd entry */
result = install_pmd
@@ -1544,6 +1584,7 @@ drop_hpage:
abort:
pte_unmap_unlock(start_pte, ptl);
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
goto drop_hpage;
}
@@ -1600,7 +1641,8 @@ static int retract_page_tables(struct address_space *mapping, pgoff_t pgoff,
* An alternative would be drop the check, but check that page
* table is clear before calling pmdp_collapse_flush() under
* ptl. It has higher chance to recover THP for the VMA, but
- * has higher cost too.
+ * has higher cost too. It would also probably require locking
+ * the anon_vma.
*/
if (vma->anon_vma) {
result = SCAN_PAGE_ANON;
@@ -1702,12 +1744,12 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
{
struct address_space *mapping = file->f_mapping;
struct page *hpage;
- pgoff_t index, end = start + HPAGE_PMD_NR;
+ pgoff_t index = 0, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
int nr_none = 0, result = SCAN_SUCCEED;
bool is_shmem = shmem_file(file);
- int nr;
+ int nr = 0;
VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
@@ -1747,6 +1789,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_set(&xas, start);
for (index = start; index < end; index++) {
struct page *page = xas_next(&xas);
+ struct folio *folio;
VM_BUG_ON(index != xas.xa_index);
if (is_shmem) {
@@ -1773,8 +1816,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
}
if (xa_is_value(page) || !PageUptodate(page)) {
- struct folio *folio;
-
xas_unlock_irq(&xas);
/* swap in or instantiate fallocated page */
if (shmem_get_folio(mapping->host, index,
@@ -1862,13 +1903,15 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
goto out_unlock;
}
- if (page_mapping(page) != mapping) {
+ folio = page_folio(page);
+
+ if (folio_mapping(folio) != mapping) {
result = SCAN_TRUNCATED;
goto out_unlock;
}
- if (!is_shmem && (PageDirty(page) ||
- PageWriteback(page))) {
+ if (!is_shmem && (folio_test_dirty(folio) ||
+ folio_test_writeback(folio))) {
/*
* khugepaged only works on read-only fd, so this
* page is dirty because it hasn't been flushed
@@ -1878,20 +1921,20 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
goto out_unlock;
}
- if (isolate_lru_page(page)) {
+ if (folio_isolate_lru(folio)) {
result = SCAN_DEL_PAGE_LRU;
goto out_unlock;
}
- if (page_has_private(page) &&
- !try_to_release_page(page, GFP_KERNEL)) {
+ if (folio_has_private(folio) &&
+ !filemap_release_folio(folio, GFP_KERNEL)) {
result = SCAN_PAGE_HAS_PRIVATE;
- putback_lru_page(page);
+ folio_putback_lru(folio);
goto out_unlock;
}
- if (page_mapped(page))
- try_to_unmap(page_folio(page),
+ if (folio_mapped(folio))
+ try_to_unmap(folio,
TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH);
xas_lock_irq(&xas);
@@ -1970,6 +2013,7 @@ xa_unlocked:
if (result == SCAN_SUCCEED) {
struct page *page, *tmp;
+ struct folio *folio;
/*
* Replacing old pages with new one has succeeded, now we
@@ -1997,11 +2041,13 @@ xa_unlocked:
index++;
}
- SetPageUptodate(hpage);
- page_ref_add(hpage, HPAGE_PMD_NR - 1);
+ folio = page_folio(hpage);
+ folio_mark_uptodate(folio);
+ folio_ref_add(folio, HPAGE_PMD_NR - 1);
+
if (is_shmem)
- set_page_dirty(hpage);
- lru_cache_add(hpage);
+ folio_mark_dirty(folio);
+ folio_add_lru(folio);
/*
* Remove pte page tables, so we can re-fault the page as huge.
@@ -2059,7 +2105,8 @@ out:
mem_cgroup_uncharge(page_folio(hpage));
put_page(hpage);
}
- /* TODO: tracepoints */
+
+ trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
return result;
}
@@ -2077,6 +2124,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
present = 0;
swap = 0;
memset(cc->node_load, 0, sizeof(cc->node_load));
+ nodes_clear(cc->alloc_nmask);
rcu_read_lock();
xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) {
if (xas_retry(&xas, page))
@@ -2157,8 +2205,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
}
}
- trace_mm_khugepaged_scan_file(mm, page, file->f_path.dentry->d_iname,
- present, swap, result);
+ trace_mm_khugepaged_scan_file(mm, page, file, present, swap, result);
return result;
}
#else
@@ -2528,6 +2575,11 @@ void khugepaged_min_free_kbytes_update(void)
mutex_unlock(&khugepaged_mutex);
}
+bool current_is_khugepaged(void)
+{
+ return kthread_func(current) == khugepaged;
+}
+
static int madvise_collapse_errno(enum scan_result r)
{
/*
@@ -2576,7 +2628,6 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
if (!cc)
return -ENOMEM;
cc->is_khugepaged = false;
- cc->last_target_node = NUMA_NO_NODE;
mmgrab(mm);
lru_add_drain_all();
@@ -2602,6 +2653,7 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
}
mmap_assert_locked(mm);
memset(cc->node_load, 0, sizeof(cc->node_load));
+ nodes_clear(cc->alloc_nmask);
if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
struct file *file = get_file(vma->vm_file);
pgoff_t pgoff = linear_page_index(vma, addr);
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-11 07:59:50 +0000