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.
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.8+
---
mm/khugepaged.c | 72 ++++++++++++++++++++++---------------------------
1 file changed, 32 insertions(+), 40 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1c402d33547e..9d4e9ff1af95 100644
--- 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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ static void collapse_shmem(struct mm_struct *mm,
/* 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 */
--
2.20.0.rc0.387.gc7a69e6b6c-goog
