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Message-ID: <5de3a4f206c81c41e8b1ce5eeb245851@pinky>
Date: Tue, 07 Aug 2007 16:31:40 +0100
From: Andy Whitcroft <apw@...dowen.org>
To: Andrew Morton <akpm@...l.org>
Cc: Mel Gorman <mel@....ul.ie>, Andy Whitcroft <apw@...dowen.org>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH] synchronous lumpy: improve commentary on writeback wait
Improve code commentary on the initial writeback wait in synchronous
reclaim mode.
Signed-off-by: Andy Whitcroft <apw@...dowen.org>
---
mm/vmscan.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b1e9291..a6e65d0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -479,6 +479,14 @@ static unsigned long shrink_page_list(struct list_head *page_list,
(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
if (PageWriteback(page)) {
+ /*
+ * Synchronous reclaim is performed in two passes,
+ * first an asynchronous pass over the list to
+ * start parallel writeback, and a second synchronous
+ * pass to wait for the IO to complete. Wait here
+ * for any page for which writeback has already
+ * started.
+ */
if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
wait_on_page_writeback(page);
else
-
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