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-rw-r--r--mm/migrate.c46
1 files changed, 26 insertions, 20 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 2f2e2236daf7..6d7774ef0e6c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -727,13 +727,8 @@ static int move_to_new_page(struct page *newpage, struct page *page,
struct address_space *mapping;
int rc;
- /*
- * Block others from accessing the page when we get around to
- * establishing additional references. We are the only one
- * holding a reference to the new page at this point.
- */
- if (!trylock_page(newpage))
- BUG();
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
/* Prepare mapping for the new page.*/
newpage->index = page->index;
@@ -774,9 +769,6 @@ static int move_to_new_page(struct page *newpage, struct page *page,
remove_migration_ptes(page, newpage);
page->mapping = NULL;
}
-
- unlock_page(newpage);
-
return rc;
}
@@ -861,6 +853,17 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
}
}
+ /*
+ * Block others from accessing the new page when we get around to
+ * establishing additional references. We are usually the only one
+ * holding a reference to newpage at this point. We used to have a BUG
+ * here if trylock_page(newpage) fails, but would like to allow for
+ * cases where there might be a race with the previous use of newpage.
+ * This is much like races on refcount of oldpage: just don't BUG().
+ */
+ if (unlikely(!trylock_page(newpage)))
+ goto out_unlock;
+
if (unlikely(isolated_balloon_page(page))) {
/*
* A ballooned page does not need any special attention from
@@ -870,7 +873,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
* the page migration right away (proteced by page lock).
*/
rc = balloon_page_migrate(newpage, page, mode);
- goto out_unlock;
+ goto out_unlock_both;
}
/*
@@ -889,30 +892,27 @@ 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;
+ goto out_unlock_both;
}
- goto skip_unmap;
- }
-
- /* Establish migration ptes or remove ptes */
- if (page_mapped(page)) {
+ } else if (page_mapped(page)) {
+ /* Establish migration ptes */
try_to_unmap(page,
TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
page_was_mapped = 1;
}
-skip_unmap:
if (!page_mapped(page))
rc = move_to_new_page(newpage, page, page_was_mapped, mode);
if (rc && page_was_mapped)
remove_migration_ptes(page, page);
+out_unlock_both:
+ unlock_page(newpage);
+out_unlock:
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
-
-out_unlock:
unlock_page(page);
out:
return rc;
@@ -1056,6 +1056,9 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
if (PageAnon(hpage))
anon_vma = page_get_anon_vma(hpage);
+ if (unlikely(!trylock_page(new_hpage)))
+ goto put_anon;
+
if (page_mapped(hpage)) {
try_to_unmap(hpage,
TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
@@ -1068,6 +1071,9 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
if (rc != MIGRATEPAGE_SUCCESS && page_was_mapped)
remove_migration_ptes(hpage, hpage);
+ unlock_page(new_hpage);
+
+put_anon:
if (anon_vma)
put_anon_vma(anon_vma);