Refactor unmap_and_move() handling for the new page into a separate
function from locking and preparing the old page.
No functional change here: this is just making it easier to reuse this
part of the page migration from contexts that already locked the old page.
Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx>
---
mm/migrate.c | 115 +++++++++++++++++++++++++++++++----------------------------
1 file changed, 61 insertions(+), 54 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index ac6f4939bb59..705b320d4b35 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1000,57 +1000,14 @@ static int move_to_new_page(struct page *newpage, struct page *page,
return rc;
}
-static int __unmap_and_move(struct page *page, struct page *newpage,
- int force, enum migrate_mode mode)
+static int __unmap_and_move_locked(struct page *page, struct page *newpage,
+ enum migrate_mode mode)
{
int rc = -EAGAIN;
int page_was_mapped = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__PageMovable(page);
- if (!trylock_page(page)) {
- if (!force || mode == MIGRATE_ASYNC)
- goto out;
-
- /*
- * It's not safe for direct compaction to call lock_page.
- * For example, during page readahead pages are added locked
- * to the LRU. Later, when the IO completes the pages are
- * marked uptodate and unlocked. However, the queueing
- * could be merging multiple pages for one bio (e.g.
- * mpage_readpages). If an allocation happens for the
- * second or third page, the process can end up locking
- * the same page twice and deadlocking. Rather than
- * trying to be clever about what pages can be locked,
- * avoid the use of lock_page for direct compaction
- * altogether.
- */
- if (current->flags & PF_MEMALLOC)
- goto out;
-
- lock_page(page);
- }
-
- if (PageWriteback(page)) {
- /*
- * Only in the case of a full synchronous migration is it
- * necessary to wait for PageWriteback. In the async case,
- * the retry loop is too short and in the sync-light case,
- * the overhead of stalling is too much
- */
- switch (mode) {
- case MIGRATE_SYNC:
- case MIGRATE_SYNC_NO_COPY:
- break;
- default:
- rc = -EBUSY;
- goto out_unlock;
- }
- if (!force)
- goto out_unlock;
- wait_on_page_writeback(page);
- }
-
/*
* By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
* we cannot notice that anon_vma is freed while we migrates a page.
@@ -1077,11 +1034,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
* This is much like races on refcount of oldpage: just don't BUG().
*/
if (unlikely(!trylock_page(newpage)))
- goto out_unlock;
+ goto out;
if (unlikely(!is_lru)) {
rc = move_to_new_page(newpage, page, mode);
- goto out_unlock_both;
+ goto out_unlock;
}
/*
@@ -1100,7 +1057,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
VM_BUG_ON_PAGE(PageAnon(page), page);
if (page_has_private(page)) {
try_to_free_buffers(page);
- goto out_unlock_both;
+ goto out_unlock;
}
} else if (page_mapped(page)) {
/* Establish migration ptes */
@@ -1110,22 +1067,19 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
page_was_mapped = 1;
}
-
if (!page_mapped(page))
rc = move_to_new_page(newpage, page, mode);
if (page_was_mapped)
remove_migration_ptes(page,
rc == MIGRATEPAGE_SUCCESS ? newpage : page, false);
-
-out_unlock_both:
- unlock_page(newpage);
out_unlock:
+ unlock_page(newpage);
/* Drop an anon_vma reference if we took one */
+out:
if (anon_vma)
put_anon_vma(anon_vma);
- unlock_page(page);
-out:
+
/*
* If migration is successful, decrease refcount of the newpage
* which will not free the page because new page owner increased
@@ -1141,7 +1095,60 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
else
putback_lru_page(newpage);
}
+ return rc;
+}
+
+static int __unmap_and_move(struct page *page, struct page *newpage,
+ int force, enum migrate_mode mode)
+{
+ int rc = -EAGAIN;
+
+ if (!trylock_page(page)) {
+ if (!force || mode == MIGRATE_ASYNC)
+ goto out;
+
+ /*
+ * It's not safe for direct compaction to call lock_page.
+ * For example, during page readahead pages are added locked
+ * to the LRU. Later, when the IO completes the pages are
+ * marked uptodate and unlocked. However, the queueing
+ * could be merging multiple pages for one bio (e.g.
+ * mpage_readpages). If an allocation happens for the
+ * second or third page, the process can end up locking
+ * the same page twice and deadlocking. Rather than
+ * trying to be clever about what pages can be locked,
+ * avoid the use of lock_page for direct compaction
+ * altogether.
+ */
+ if (current->flags & PF_MEMALLOC)
+ goto out;
+
+ lock_page(page);
+ }
+ if (PageWriteback(page)) {
+ /*
+ * Only in the case of a full synchronous migration is it
+ * necessary to wait for PageWriteback. In the async case,
+ * the retry loop is too short and in the sync-light case,
+ * the overhead of stalling is too much
+ */
+ switch (mode) {
+ case MIGRATE_SYNC:
+ case MIGRATE_SYNC_NO_COPY:
+ break;
+ default:
+ rc = -EBUSY;
+ goto out_unlock;
+ }
+ if (!force)
+ goto out_unlock;
+ wait_on_page_writeback(page);
+ }
+ rc = __unmap_and_move_locked(page, newpage, mode);
+out_unlock:
+ unlock_page(page);
+out:
return rc;
}
--
2.14.4
