Terminate the write_cache_pages loop upon encountering the first page past
end, without locking the page. Pages cannot have their index change when we
have a reference on them (truncate, eg truncate_inode_pages_range performs
the same check without the page lock).
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -913,12 +913,18 @@ retry:
struct page *page = pvec.pages[i];
/*
- * At this point we hold neither mapping->tree_lock nor
- * lock on the page itself: the page may be truncated or
- * invalidated (changing page->mapping to NULL), or even
- * swizzled back from swapper_space to tmpfs file
- * mapping
+ * At this point, the page may be truncated or
+ * invalidated (changing page->mapping to NULL), or
+ * even swizzled back from swapper_space to tmpfs file
+ * mapping. However, page->index will not change
+ * because we have a reference on the page.
*/
+ if (page->index > end) {
+ /* Can't be range_cyclic: end == -1 there */
+ done = 1;
+ break;
+ }
+
again:
lock_page(page);
@@ -936,12 +942,6 @@ continue_unlock:
continue;
}
- if (page->index > end) {
- /* Can't be range_cyclic: end == -1 there */
- done = 1;
- goto continue_unlock;
- }
-
if (!PageDirty(page)) {
/* someone wrote it for us */
goto continue_unlock;
--
--
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