mm/khugepaged: minor reorderings in collapse_shmem()

Several cleanups in collapse_shmem(): most of which probably do not
really matter, beyond doing things in a more familiar and reassuring
order.  Simplify the failure gotos in the main loop, and on success
update stats while interrupts still disabled from the last iteration.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261526400.2275@eggly.anvils
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1c402d33547e43ca8503f308064ea2e0167de2ce..9d4e9ff1af95ebf444b14d63449bcb4214236ab2 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1329,10 +1329,10 @@ static void collapse_shmem(struct mm_struct *mm,
                goto out;
        }
 
+       __SetPageLocked(new_page);
+       __SetPageSwapBacked(new_page);
        new_page->index = start;
        new_page->mapping = mapping;
-       __SetPageSwapBacked(new_page);
-       __SetPageLocked(new_page);
        BUG_ON(!page_ref_freeze(new_page, 1));
 
        /*
@@ -1366,13 +1366,13 @@ static void collapse_shmem(struct mm_struct *mm,
                        if (index == start) {
                                if (!xas_next_entry(&xas, end - 1)) {
                                        result = SCAN_TRUNCATED;
-                                       break;
+                                       goto xa_locked;
                                }
                                xas_set(&xas, index);
                        }
                        if (!shmem_charge(mapping->host, 1)) {
                                result = SCAN_FAIL;
-                               break;
+                               goto xa_locked;
                        }
                        xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
                        nr_none++;
@@ -1387,13 +1387,12 @@ static void collapse_shmem(struct mm_struct *mm,
                                result = SCAN_FAIL;
                                goto xa_unlocked;
                        }
-                       xas_lock_irq(&xas);
-                       xas_set(&xas, index);
                } else if (trylock_page(page)) {
                        get_page(page);
+                       xas_unlock_irq(&xas);
                } else {
                        result = SCAN_PAGE_LOCK;
-                       break;
+                       goto xa_locked;
                }
 
                /*
@@ -1408,11 +1407,10 @@ static void collapse_shmem(struct mm_struct *mm,
                        result = SCAN_TRUNCATED;
                        goto out_unlock;
                }
-               xas_unlock_irq(&xas);
 
                if (isolate_lru_page(page)) {
                        result = SCAN_DEL_PAGE_LRU;
-                       goto out_isolate_failed;
+                       goto out_unlock;
                }
 
                if (page_mapped(page))
@@ -1432,7 +1430,9 @@ static void collapse_shmem(struct mm_struct *mm,
                 */
                if (!page_ref_freeze(page, 3)) {
                        result = SCAN_PAGE_COUNT;
-                       goto out_lru;
+                       xas_unlock_irq(&xas);
+                       putback_lru_page(page);
+                       goto out_unlock;
                }
 
                /*
@@ -1444,24 +1444,26 @@ static void collapse_shmem(struct mm_struct *mm,
                /* Finally, replace with the new page. */
                xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
                continue;
-out_lru:
-               xas_unlock_irq(&xas);
-               putback_lru_page(page);
-out_isolate_failed:
-               unlock_page(page);
-               put_page(page);
-               goto xa_unlocked;
 out_unlock:
                unlock_page(page);
                put_page(page);
-               break;
+               goto xa_unlocked;
        }
-       xas_unlock_irq(&xas);
 
+       __inc_node_page_state(new_page, NR_SHMEM_THPS);
+       if (nr_none) {
+               struct zone *zone = page_zone(new_page);
+
+               __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
+               __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
+       }
+
+xa_locked:
+       xas_unlock_irq(&xas);
 xa_unlocked:
+
        if (result == SCAN_SUCCEED) {
                struct page *page, *tmp;
-               struct zone *zone = page_zone(new_page);
 
                /*
                 * Replacing old pages with new one has succeeded, now we
@@ -1476,11 +1478,11 @@ xa_unlocked:
                        copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
                                        page);
                        list_del(&page->lru);
-                       unlock_page(page);
-                       page_ref_unfreeze(page, 1);
                        page->mapping = NULL;
+                       page_ref_unfreeze(page, 1);
                        ClearPageActive(page);
                        ClearPageUnevictable(page);
+                       unlock_page(page);
                        put_page(page);
                        index++;
                }
@@ -1489,28 +1491,17 @@ xa_unlocked:
                        index++;
                }
 
-               local_irq_disable();
-               __inc_node_page_state(new_page, NR_SHMEM_THPS);
-               if (nr_none) {
-                       __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
-                       __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
-               }
-               local_irq_enable();
-
-               /*
-                * Remove pte page tables, so we can re-fault
-                * the page as huge.
-                */
-               retract_page_tables(mapping, start);
-
                /* Everything is ready, let's unfreeze the new_page */
-               set_page_dirty(new_page);
                SetPageUptodate(new_page);
                page_ref_unfreeze(new_page, HPAGE_PMD_NR);
+               set_page_dirty(new_page);
                mem_cgroup_commit_charge(new_page, memcg, false, true);
                lru_cache_add_anon(new_page);
-               unlock_page(new_page);
 
+               /*
+                * Remove pte page tables, so we can re-fault the page as huge.
+                */
+               retract_page_tables(mapping, start);
                *hpage = NULL;
 
                khugepaged_pages_collapsed++;
@@ -1543,8 +1534,8 @@ xa_unlocked:
                        xas_store(&xas, page);
                        xas_pause(&xas);
                        xas_unlock_irq(&xas);
-                       putback_lru_page(page);
                        unlock_page(page);
+                       putback_lru_page(page);
                        xas_lock_irq(&xas);
                }
                VM_BUG_ON(nr_none);
@@ -1553,9 +1544,10 @@ xa_unlocked:
                /* Unfreeze new_page, caller would take care about freeing it */
                page_ref_unfreeze(new_page, 1);
                mem_cgroup_cancel_charge(new_page, memcg, true);
-               unlock_page(new_page);
                new_page->mapping = NULL;
        }
+
+       unlock_page(new_page);
 out:
        VM_BUG_ON(!list_empty(&pagelist));
        /* TODO: tracepoints */