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authorNick Piggin <npiggin@suse.de>2009-01-06 14:39:11 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2009-01-24 16:36:27 -0800
commite55e8f16723d5017aff16547e259e2c35766e4ad (patch)
treeaf78dedd810f767a1d5c8e8e56800bcfa94f82c4
parent65cdf4090b2a70726bed638e7c41bb3f952d0076 (diff)
downloadlinux-linaro-stable-e55e8f16723d5017aff16547e259e2c35766e4ad.tar.gz
mm: write_cache_pages terminate quickly
commit d5482cdf8a0aacb1e6468a97d5544f5829c8d8c4 upstream. 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@suse.de> Cc: Chris Mason <chris.mason@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--mm/page-writeback.c32
1 files changed, 16 insertions, 16 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index d69548daf3b2..0f225bf6b8ed 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -914,15 +914,24 @@ retry:
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
- done_index = page->index + 1;
-
/*
- * 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 (1st pass) because
+ * end == -1 in that case.
+ */
+ done = 1;
+ break;
+ }
+
+ done_index = page->index + 1;
+
lock_page(page);
/*
@@ -939,15 +948,6 @@ continue_unlock:
continue;
}
- if (page->index > end) {
- /*
- * can't be range_cyclic (1st pass) because
- * end == -1 in that case.
- */
- done = 1;
- goto continue_unlock;
- }
-
if (!PageDirty(page)) {
/* someone wrote it for us */
goto continue_unlock;