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The wb_thresh bumping logic is scattered across wb_position_ratio, __wb_calc_thresh, and wb_update_dirty_ratelimit. For consistency, consolidate all wb_thresh bumping logic into __wb_calc_thresh. Reviewed-by: Jan Kara Signed-off-by: Jim Zhao --- mm/page-writeback.c | 53 ++++++++++++++------------------------------- 1 file changed, 16 insertions(+), 37 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index d213ead95675..8b13bcb42de3 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -936,26 +936,25 @@ static unsigned long __wb_calc_thresh(struct dirty_th= rottle_control *dtc, wb_min_max_ratio(wb, &wb_min_ratio, &wb_max_ratio); =20 wb_thresh +=3D (thresh * wb_min_ratio) / (100 * BDI_RATIO_SCALE); - wb_max_thresh =3D thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE); - if (wb_thresh > wb_max_thresh) - wb_thresh =3D wb_max_thresh; =20 /* - * With strictlimit flag, the wb_thresh is treated as - * a hard limit in balance_dirty_pages() and wb_position_ratio(). - * It's possible that wb_thresh is close to zero, not because - * the device is slow, but because it has been inactive. - * To prevent occasional writes from being blocked, we raise wb_thresh. + * It's very possible that wb_thresh is close to 0 not because the + * device is slow, but that it has remained inactive for long time. + * Honour such devices a reasonable good (hopefully IO efficient) + * threshold, so that the occasional writes won't be blocked and active + * writes can rampup the threshold quickly. */ - if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { - unsigned long limit =3D hard_dirty_limit(dom, dtc->thresh); - u64 wb_scale_thresh =3D 0; - - if (limit > dtc->dirty) - wb_scale_thresh =3D (limit - dtc->dirty) / 100; - wb_thresh =3D max(wb_thresh, min(wb_scale_thresh, wb_max_thresh / 4)); + if (thresh > dtc->dirty) { + if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) + wb_thresh =3D max(wb_thresh, (thresh - dtc->dirty) / 100); + else + wb_thresh =3D max(wb_thresh, (thresh - dtc->dirty) / 8); } =20 + wb_max_thresh =3D thresh * wb_max_ratio / (100 * BDI_RATIO_SCALE); + if (wb_thresh > wb_max_thresh) + wb_thresh =3D wb_max_thresh; + return wb_thresh; } =20 @@ -963,6 +962,7 @@ unsigned long wb_calc_thresh(struct bdi_writeback *wb, = unsigned long thresh) { struct dirty_throttle_control gdtc =3D { GDTC_INIT(wb) }; =20 + domain_dirty_avail(&gdtc, true); return __wb_calc_thresh(&gdtc, thresh); } =20 @@ -1139,12 +1139,6 @@ static void wb_position_ratio(struct dirty_throttle_= control *dtc) if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { long long wb_pos_ratio; =20 - if (dtc->wb_dirty < 8) { - dtc->pos_ratio =3D min_t(long long, pos_ratio * 2, - 2 << RATELIMIT_CALC_SHIFT); - return; - } - if (dtc->wb_dirty >=3D wb_thresh) return; =20 @@ -1215,14 +1209,6 @@ static void wb_position_ratio(struct dirty_throttle_= control *dtc) */ if (unlikely(wb_thresh > dtc->thresh)) wb_thresh =3D dtc->thresh; - /* - * It's very possible that wb_thresh is close to 0 not because the - * device is slow, but that it has remained inactive for long time. - * Honour such devices a reasonable good (hopefully IO efficient) - * threshold, so that the occasional writes won't be blocked and active - * writes can rampup the threshold quickly. - */ - wb_thresh =3D max(wb_thresh, (limit - dtc->dirty) / 8); /* * scale global setpoint to wb's: * wb_setpoint =3D setpoint * wb_thresh / thresh @@ -1478,17 +1464,10 @@ static void wb_update_dirty_ratelimit(struct dirty_= throttle_control *dtc, * balanced_dirty_ratelimit =3D task_ratelimit * write_bw / dirty_rate). * Hence, to calculate "step" properly, we have to use wb_dirty as * "dirty" and wb_setpoint as "setpoint". - * - * We rampup dirty_ratelimit forcibly if wb_dirty is low because - * it's possible that wb_thresh is close to zero due to inactivity - * of backing device. */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { dirty =3D dtc->wb_dirty; - if (dtc->wb_dirty < 8) - setpoint =3D dtc->wb_dirty + 1; - else - setpoint =3D (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; + setpoint =3D (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; } =20 if (dirty < setpoint) { --=20 2.20.1