The loop is no longer necessary. Remove it without behavior change. Signed-off-by: Wu Fengguang --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/