mm/khugepaged: minor reorderings in collapse_shmem()

commit 042a30824871fa3149b0127009074b75cc25863c upstream.

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2d3ce49..47b8303 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1332,13 +1332,12 @@ 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));
 
-
        /*
         * At this point the new_page is 'frozen' (page_count() is zero), locked
         * and not up-to-date. It's safe to insert it into radix tree, because
@@ -1367,13 +1366,13 @@ static void collapse_shmem(struct mm_struct *mm,
                 */
                if (n && !shmem_charge(mapping->host, n)) {
                        result = SCAN_FAIL;
-                       break;
+                       goto tree_locked;
                }
-               nr_none += n;
                for (; index < min(iter.index, end); index++) {
                        radix_tree_insert(&mapping->page_tree, index,
                                        new_page + (index % HPAGE_PMD_NR));
                }
+               nr_none += n;
 
                /* We are done. */
                if (index >= end)
@@ -1389,12 +1388,12 @@ static void collapse_shmem(struct mm_struct *mm,
                                result = SCAN_FAIL;
                                goto tree_unlocked;
                        }
-                       spin_lock_irq(&mapping->tree_lock);
                } else if (trylock_page(page)) {
                        get_page(page);
+                       spin_unlock_irq(&mapping->tree_lock);
                } else {
                        result = SCAN_PAGE_LOCK;
-                       break;
+                       goto tree_locked;
                }
 
                /*
@@ -1409,11 +1408,10 @@ static void collapse_shmem(struct mm_struct *mm,
                        result = SCAN_TRUNCATED;
                        goto out_unlock;
                }
-               spin_unlock_irq(&mapping->tree_lock);
 
                if (isolate_lru_page(page)) {
                        result = SCAN_DEL_PAGE_LRU;
-                       goto out_isolate_failed;
+                       goto out_unlock;
                }
 
                if (page_mapped(page))
@@ -1435,7 +1433,9 @@ static void collapse_shmem(struct mm_struct *mm,
                 */
                if (!page_ref_freeze(page, 3)) {
                        result = SCAN_PAGE_COUNT;
-                       goto out_lru;
+                       spin_unlock_irq(&mapping->tree_lock);
+                       putback_lru_page(page);
+                       goto out_unlock;
                }
 
                /*
@@ -1451,17 +1451,10 @@ static void collapse_shmem(struct mm_struct *mm,
                slot = radix_tree_iter_next(&iter);
                index++;
                continue;
-out_lru:
-               spin_unlock_irq(&mapping->tree_lock);
-               putback_lru_page(page);
-out_isolate_failed:
-               unlock_page(page);
-               put_page(page);
-               goto tree_unlocked;
 out_unlock:
                unlock_page(page);
                put_page(page);
-               break;
+               goto tree_unlocked;
        }
 
        /*
@@ -1469,7 +1462,7 @@ out_unlock:
         * This code only triggers if there's nothing in radix tree
         * beyond 'end'.
         */
-       if (result == SCAN_SUCCEED && index < end) {
+       if (index < end) {
                int n = end - index;
 
                /* Stop if extent has been truncated, and is now empty */
@@ -1481,7 +1474,6 @@ out_unlock:
                        result = SCAN_FAIL;
                        goto tree_locked;
                }
-
                for (; index < end; index++) {
                        radix_tree_insert(&mapping->page_tree, index,
                                        new_page + (index % HPAGE_PMD_NR));
@@ -1489,14 +1481,19 @@ out_unlock:
                nr_none += n;
        }
 
+       __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);
+       }
+
 tree_locked:
        spin_unlock_irq(&mapping->tree_lock);
 tree_unlocked:
 
        if (result == SCAN_SUCCEED) {
-               unsigned long flags;
-               struct zone *zone = page_zone(new_page);
-
                /*
                 * Replacing old pages with new one has succeed, now we need to
                 * copy the content and free old pages.
@@ -1510,11 +1507,11 @@ tree_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++;
                }
@@ -1523,28 +1520,17 @@ tree_unlocked:
                        index++;
                }
 
-               local_irq_save(flags);
-               __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_restore(flags);
-
-               /*
-                * Remove pte page tables, so we can re-faulti
-                * 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;
        } else {
                /* Something went wrong: rollback changes to the radix-tree */
@@ -1576,8 +1562,8 @@ tree_unlocked:
                        page_ref_unfreeze(page, 2);
                        radix_tree_replace_slot(slot, page);
                        spin_unlock_irq(&mapping->tree_lock);
-                       putback_lru_page(page);
                        unlock_page(page);
+                       putback_lru_page(page);
                        spin_lock_irq(&mapping->tree_lock);
                        slot = radix_tree_iter_next(&iter);
                }
@@ -1587,9 +1573,10 @@ tree_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 */