[patch 12/47] writeback: fix break condition

Greg KH
2009-02-14T01:05:52Z

[-- Attachment #1: writeback-fix-break-condition.patch --]
[-- Type: text/plain, Size: 2061 bytes --]

2.6.27-stable review patch. If anyone has any objections, please let us know.

------------------

From: Federico Cuello <fedux@lugmen.org.ar>

commit 89e1219004b3657cc014521663eeef0744f1c99d upstream.

Commit dcf6a79dda5cc2a2bec183e50d829030c0972aaa ("write-back: fix
nr_to_write counter") fixed nr_to_write counter, but didn't set the break
condition properly.

If nr_to_write == 0 after being decremented it will loop one more time
before setting done = 1 and breaking the loop.

[akpm@linux-foundation.org: coding-style fixes]
Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: Nick Piggin <npiggin@suse.de>
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>

---
mm/page-writeback.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -985,20 +985,23 @@ continue_unlock:
}
}

- if (wbc->nr_to_write > 0)
+ if (wbc->nr_to_write > 0) {
wbc->nr_to_write--;
- else if (wbc->sync_mode == WB_SYNC_NONE) {
- /*
- * We stop writing back only if we are not
- * doing integrity sync. In case of integrity
- * sync we have to keep going because someone
- * may be concurrently dirtying pages, and we
- * might have synced a lot of newly appeared
- * dirty pages, but have not synced all of the
- * old dirty pages.
- */
- done = 1;
- break;
+ if (wbc->nr_to_write == 0 &&
+ wbc->sync_mode == WB_SYNC_NONE) {
+ /*
+ * We stop writing back only if we are
+ * not doing integrity sync. In case of
+ * integrity sync we have to keep going
+ * because someone may be concurrently
+ * dirtying pages, and we might have
+ * synced a lot of newly appeared dirty
+ * pages, but have not synced all of the
+ * old dirty pages.
+ */
+ done = 1;
+ break;
+ }
}

if (wbc->nonblocking && bdi_write_congested(bdi)) {