The loop is no longer necessary. Remove it without behavior change.
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
mm/page-writeback.c | 81 +++++++++++++++++++-----------------------
1 file changed, 38 insertions(+), 43 deletions(-)
--- linux.orig/mm/page-writeback.c 2009-10-06 23:38:43.000000000 +0800
+++ linux/mm/page-writeback.c 2009-10-06 23:38:43.000000000 +0800
@@ -470,60 +470,55 @@ static void balance_dirty_pages(struct a
int dirty_exceeded;
struct backing_dev_info *bdi = mapping->backing_dev_info;
- for (;;) {
- nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
- nr_writeback = global_page_state(NR_WRITEBACK) +
- global_page_state(NR_WRITEBACK_TEMP);
+ nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
+ nr_writeback = global_page_state(NR_WRITEBACK) +
+ global_page_state(NR_WRITEBACK_TEMP);
- global_dirty_thresh(&background_thresh, &dirty_thresh);
-
- /*
- * Throttle it only when the background writeback cannot
- * catch-up. This avoids (excessively) small writeouts
- * when the bdi limits are ramping up.
- */
- if (nr_reclaimable + nr_writeback <
- (background_thresh + dirty_thresh) / 2)
- break;
+ global_dirty_thresh(&background_thresh, &dirty_thresh);
- bdi_thresh = bdi_dirty_thresh(bdi, dirty_thresh);
+ /*
+ * Throttle it only when the background writeback cannot
+ * catch-up. This skips the ramp up phase of bdi limits.
+ */
+ if (nr_reclaimable + nr_writeback <
+ (background_thresh + dirty_thresh) / 2)
+ goto out;
- /*
- * In order to avoid the stacked BDI deadlock we need
- * to ensure we accurately count the 'dirty' pages when
- * the threshold is low.
- *
- * Otherwise it would be possible to get thresh+n pages
- * reported dirty, even though there are thresh-m pages
- * actually dirty; with m+n sitting in the percpu
- * deltas.
- */
- if (bdi_thresh < 2*bdi_stat_error(bdi)) {
- bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
- bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
- } else {
- bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
- bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
- }
+ bdi_thresh = bdi_dirty_thresh(bdi, dirty_thresh);
+ /*
+ * In order to avoid the stacked BDI deadlock we need
+ * to ensure we accurately count the 'dirty' pages when
+ * the threshold is low.
+ *
+ * Otherwise it would be possible to get thresh+n pages
+ * reported dirty, even though there are thresh-m pages
+ * actually dirty; with m+n sitting in the percpu
+ * deltas.
+ */
+ if (bdi_thresh >= 2 * bdi_stat_error(bdi)) {
+ bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
+ bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+ } else {
+ bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
+ bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
+ }
- dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
+ dirty_exceeded = (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
|| (nr_reclaimable + nr_writeback >= dirty_thresh);
- if (!dirty_exceeded)
- break;
+ if (!dirty_exceeded)
+ goto out;
- if (!bdi->dirty_exceeded)
- bdi->dirty_exceeded = 1;
+ if (!bdi->dirty_exceeded)
+ bdi->dirty_exceeded = 1;
- bdi_writeback_wait(bdi, write_chunk);
- break;
- }
+ bdi_writeback_wait(bdi, write_chunk);
- if (!dirty_exceeded && bdi->dirty_exceeded)
+ if (bdi->dirty_exceeded)
bdi->dirty_exceeded = 0;
+out:
/*
* In laptop mode, we wait until hitting the higher threshold before
* starting background writeout, and then write out all the way down
--
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