[PATCH 4.9 10/50] mm/khugepaged: minor reorderings in collapse_shmem()

Greg Kroah-Hartman
2018-12-04T11:07:42Z

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>
---
mm/khugepaged.c | 73 ++++++++++++++++++++-----------------------------
1 file changed, 30 insertions(+), 43 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2d3ce49f6b45..47b83030fc53 100644
--- 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 @@ static void collapse_shmem(struct mm_struct *mm,
* 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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ 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++;
}
@@ -1523,28 +1520,17 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ static void collapse_shmem(struct mm_struct *mm,
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 @@ 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 */
--
2.17.1