Improve code commentary on the initial writeback wait in synchronous
reclaim mode.
Signed-off-by: Andy Whitcroft <[email protected]>
---
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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