diff options
Diffstat (limited to 'mm/page-writeback.c')
| -rw-r--r-- | mm/page-writeback.c | 270 |
1 files changed, 134 insertions, 136 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index cd39ee91b7bb..78ef5511a198 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -595,7 +595,7 @@ static long long pos_ratio_polynom(unsigned long setpoint, * * (o) global/bdi setpoints * - * We want the dirty pages be balanced around the global/bdi setpoints. + * We want the dirty pages be balanced around the global/wb setpoints. * When the number of dirty pages is higher/lower than the setpoint, the * dirty position control ratio (and hence task dirty ratelimit) will be * decreased/increased to bring the dirty pages back to the setpoint. @@ -605,8 +605,8 @@ static long long pos_ratio_polynom(unsigned long setpoint, * if (dirty < setpoint) scale up pos_ratio * if (dirty > setpoint) scale down pos_ratio * - * if (bdi_dirty < bdi_setpoint) scale up pos_ratio - * if (bdi_dirty > bdi_setpoint) scale down pos_ratio + * if (wb_dirty < wb_setpoint) scale up pos_ratio + * if (wb_dirty > wb_setpoint) scale down pos_ratio * * task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT * @@ -631,7 +631,7 @@ static long long pos_ratio_polynom(unsigned long setpoint, * 0 +------------.------------------.----------------------*-------------> * freerun^ setpoint^ limit^ dirty pages * - * (o) bdi control line + * (o) wb control line * * ^ pos_ratio * | @@ -657,27 +657,27 @@ static long long pos_ratio_polynom(unsigned long setpoint, * | . . * | . . * 0 +----------------------.-------------------------------.-------------> - * bdi_setpoint^ x_intercept^ + * wb_setpoint^ x_intercept^ * - * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can + * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can * be smoothly throttled down to normal if it starts high in situations like * - start writing to a slow SD card and a fast disk at the same time. The SD - * card's bdi_dirty may rush to many times higher than bdi_setpoint. - * - the bdi dirty thresh drops quickly due to change of JBOD workload + * card's wb_dirty may rush to many times higher than wb_setpoint. + * - the wb dirty thresh drops quickly due to change of JBOD workload */ static unsigned long wb_position_ratio(struct bdi_writeback *wb, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, - unsigned long bdi_thresh, - unsigned long bdi_dirty) + unsigned long wb_thresh, + unsigned long wb_dirty) { unsigned long write_bw = wb->avg_write_bandwidth; unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh); unsigned long limit = hard_dirty_limit(thresh); unsigned long x_intercept; unsigned long setpoint; /* dirty pages' target balance point */ - unsigned long bdi_setpoint; + unsigned long wb_setpoint; unsigned long span; long long pos_ratio; /* for scaling up/down the rate limit */ long x; @@ -696,146 +696,145 @@ static unsigned long wb_position_ratio(struct bdi_writeback *wb, /* * The strictlimit feature is a tool preventing mistrusted filesystems * from growing a large number of dirty pages before throttling. For - * such filesystems balance_dirty_pages always checks bdi counters - * against bdi limits. Even if global "nr_dirty" is under "freerun". + * such filesystems balance_dirty_pages always checks wb counters + * against wb limits. Even if global "nr_dirty" is under "freerun". * This is especially important for fuse which sets bdi->max_ratio to * 1% by default. Without strictlimit feature, fuse writeback may * consume arbitrary amount of RAM because it is accounted in * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". * * Here, in wb_position_ratio(), we calculate pos_ratio based on - * two values: bdi_dirty and bdi_thresh. Let's consider an example: + * two values: wb_dirty and wb_thresh. Let's consider an example: * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global * limits are set by default to 10% and 20% (background and throttle). - * Then bdi_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. - * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. bdi_setpoint is - * about ~6K pages (as the average of background and throttle bdi + * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages. + * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. wb_setpoint is + * about ~6K pages (as the average of background and throttle wb * limits). The 3rd order polynomial will provide positive feedback if - * bdi_dirty is under bdi_setpoint and vice versa. + * wb_dirty is under wb_setpoint and vice versa. * * Note, that we cannot use global counters in these calculations - * because we want to throttle process writing to a strictlimit BDI + * because we want to throttle process writing to a strictlimit wb * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB * in the example above). */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { - long long bdi_pos_ratio; - unsigned long bdi_bg_thresh; + long long wb_pos_ratio; + unsigned long wb_bg_thresh; - if (bdi_dirty < 8) + if (wb_dirty < 8) return min_t(long long, pos_ratio * 2, 2 << RATELIMIT_CALC_SHIFT); - if (bdi_dirty >= bdi_thresh) + if (wb_dirty >= wb_thresh) return 0; - bdi_bg_thresh = div_u64((u64)bdi_thresh * bg_thresh, thresh); - bdi_setpoint = dirty_freerun_ceiling(bdi_thresh, - bdi_bg_thresh); + wb_bg_thresh = div_u64((u64)wb_thresh * bg_thresh, thresh); + wb_setpoint = dirty_freerun_ceiling(wb_thresh, wb_bg_thresh); - if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh) + if (wb_setpoint == 0 || wb_setpoint == wb_thresh) return 0; - bdi_pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty, - bdi_thresh); + wb_pos_ratio = pos_ratio_polynom(wb_setpoint, wb_dirty, + wb_thresh); /* - * Typically, for strictlimit case, bdi_setpoint << setpoint - * and pos_ratio >> bdi_pos_ratio. In the other words global + * Typically, for strictlimit case, wb_setpoint << setpoint + * and pos_ratio >> wb_pos_ratio. In the other words global * state ("dirty") is not limiting factor and we have to - * make decision based on bdi counters. But there is an + * make decision based on wb counters. But there is an * important case when global pos_ratio should get precedence: * global limits are exceeded (e.g. due to activities on other - * BDIs) while given strictlimit BDI is below limit. + * wb's) while given strictlimit wb is below limit. * - * "pos_ratio * bdi_pos_ratio" would work for the case above, + * "pos_ratio * wb_pos_ratio" would work for the case above, * but it would look too non-natural for the case of all - * activity in the system coming from a single strictlimit BDI + * activity in the system coming from a single strictlimit wb * with bdi->max_ratio == 100%. * * Note that min() below somewhat changes the dynamics of the * control system. Normally, pos_ratio value can be well over 3 - * (when globally we are at freerun and bdi is well below bdi + * (when globally we are at freerun and wb is well below wb * setpoint). Now the maximum pos_ratio in the same situation * is 2. We might want to tweak this if we observe the control * system is too slow to adapt. */ - return min(pos_ratio, bdi_pos_ratio); + return min(pos_ratio, wb_pos_ratio); } /* * We have computed basic pos_ratio above based on global situation. If - * the bdi is over/under its share of dirty pages, we want to scale + * the wb is over/under its share of dirty pages, we want to scale * pos_ratio further down/up. That is done by the following mechanism. */ /* - * bdi setpoint + * wb setpoint * - * f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint) + * f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint) * - * x_intercept - bdi_dirty + * x_intercept - wb_dirty * := -------------------------- - * x_intercept - bdi_setpoint + * x_intercept - wb_setpoint * - * The main bdi control line is a linear function that subjects to + * The main wb control line is a linear function that subjects to * - * (1) f(bdi_setpoint) = 1.0 - * (2) k = - 1 / (8 * write_bw) (in single bdi case) - * or equally: x_intercept = bdi_setpoint + 8 * write_bw + * (1) f(wb_setpoint) = 1.0 + * (2) k = - 1 / (8 * write_bw) (in single wb case) + * or equally: x_intercept = wb_setpoint + 8 * write_bw * - * For single bdi case, the dirty pages are observed to fluctuate + * For single wb case, the dirty pages are observed to fluctuate * regularly within range - * [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2] + * [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2] * for various filesystems, where (2) can yield in a reasonable 12.5% * fluctuation range for pos_ratio. * - * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its + * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its * own size, so move the slope over accordingly and choose a slope that - * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh. + * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh. */ - if (unlikely(bdi_thresh > thresh)) - bdi_thresh = thresh; + if (unlikely(wb_thresh > thresh)) + wb_thresh = thresh; /* - * It's very possible that bdi_thresh is close to 0 not because the + * 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. */ - bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); + wb_thresh = max(wb_thresh, (limit - dirty) / 8); /* - * scale global setpoint to bdi's: - * bdi_setpoint = setpoint * bdi_thresh / thresh + * scale global setpoint to wb's: + * wb_setpoint = setpoint * wb_thresh / thresh */ - x = div_u64((u64)bdi_thresh << 16, thresh + 1); - bdi_setpoint = setpoint * (u64)x >> 16; + x = div_u64((u64)wb_thresh << 16, thresh + 1); + wb_setpoint = setpoint * (u64)x >> 16; /* - * Use span=(8*write_bw) in single bdi case as indicated by - * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case. + * Use span=(8*write_bw) in single wb case as indicated by + * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case. * - * bdi_thresh thresh - bdi_thresh - * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh - * thresh thresh + * wb_thresh thresh - wb_thresh + * span = --------- * (8 * write_bw) + ------------------ * wb_thresh + * thresh thresh */ - span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16; - x_intercept = bdi_setpoint + span; + span = (thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16; + x_intercept = wb_setpoint + span; - if (bdi_dirty < x_intercept - span / 4) { - pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty), - x_intercept - bdi_setpoint + 1); + if (wb_dirty < x_intercept - span / 4) { + pos_ratio = div64_u64(pos_ratio * (x_intercept - wb_dirty), + x_intercept - wb_setpoint + 1); } else pos_ratio /= 4; /* - * bdi reserve area, safeguard against dirty pool underrun and disk idle + * wb reserve area, safeguard against dirty pool underrun and disk idle * It may push the desired control point of global dirty pages higher * than setpoint. */ - x_intercept = bdi_thresh / 2; - if (bdi_dirty < x_intercept) { - if (bdi_dirty > x_intercept / 8) - pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty); + x_intercept = wb_thresh / 2; + if (wb_dirty < x_intercept) { + if (wb_dirty > x_intercept / 8) + pos_ratio = div_u64(pos_ratio * x_intercept, wb_dirty); else pos_ratio *= 8; } @@ -943,17 +942,17 @@ static void global_update_bandwidth(unsigned long thresh, } /* - * Maintain bdi->dirty_ratelimit, the base dirty throttle rate. + * Maintain wb->dirty_ratelimit, the base dirty throttle rate. * - * Normal bdi tasks will be curbed at or below it in long term. + * Normal wb tasks will be curbed at or below it in long term. * Obviously it should be around (write_bw / N) when there are N dd tasks. */ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, - unsigned long bdi_thresh, - unsigned long bdi_dirty, + unsigned long wb_thresh, + unsigned long wb_dirty, unsigned long dirtied, unsigned long elapsed) { @@ -976,7 +975,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; pos_ratio = wb_position_ratio(wb, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty); + wb_thresh, wb_dirty); /* * task_ratelimit reflects each dd's dirty rate for the past 200ms. */ @@ -986,7 +985,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, /* * A linear estimation of the "balanced" throttle rate. The theory is, - * if there are N dd tasks, each throttled at task_ratelimit, the bdi's + * if there are N dd tasks, each throttled at task_ratelimit, the wb's * dirty_rate will be measured to be (N * task_ratelimit). So the below * formula will yield the balanced rate limit (write_bw / N). * @@ -1025,7 +1024,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, /* * We could safely do this and return immediately: * - * bdi->dirty_ratelimit = balanced_dirty_ratelimit; + * wb->dirty_ratelimit = balanced_dirty_ratelimit; * * However to get a more stable dirty_ratelimit, the below elaborated * code makes use of task_ratelimit to filter out singular points and @@ -1059,22 +1058,22 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, step = 0; /* - * For strictlimit case, calculations above were based on bdi counters + * For strictlimit case, calculations above were based on wb counters * and limits (starting from pos_ratio = wb_position_ratio() and up to * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate). - * Hence, to calculate "step" properly, we have to use bdi_dirty as - * "dirty" and bdi_setpoint as "setpoint". + * Hence, to calculate "step" properly, we have to use wb_dirty as + * "dirty" and wb_setpoint as "setpoint". * - * We rampup dirty_ratelimit forcibly if bdi_dirty is low because - * it's possible that bdi_thresh is close to zero due to inactivity + * 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 (see the implementation of wb_dirty_limit()). */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { - dirty = bdi_dirty; - if (bdi_dirty < 8) - setpoint = bdi_dirty + 1; + dirty = wb_dirty; + if (wb_dirty < 8) + setpoint = wb_dirty + 1; else - setpoint = (bdi_thresh + + setpoint = (wb_thresh + wb_dirty_limit(wb, bg_thresh)) / 2; } @@ -1116,8 +1115,8 @@ void __wb_update_bandwidth(struct bdi_writeback *wb, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, - unsigned long bdi_thresh, - unsigned long bdi_dirty, + unsigned long wb_thresh, + unsigned long wb_dirty, unsigned long start_time) { unsigned long now = jiffies; @@ -1144,7 +1143,7 @@ void __wb_update_bandwidth(struct bdi_writeback *wb, if (thresh) { global_update_bandwidth(thresh, dirty, now); wb_update_dirty_ratelimit(wb, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty, + wb_thresh, wb_dirty, dirtied, elapsed); } wb_update_write_bandwidth(wb, elapsed, written); @@ -1159,15 +1158,15 @@ static void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long thresh, unsigned long bg_thresh, unsigned long dirty, - unsigned long bdi_thresh, - unsigned long bdi_dirty, + unsigned long wb_thresh, + unsigned long wb_dirty, unsigned long start_time) { if (time_is_after_eq_jiffies(wb->bw_time_stamp + BANDWIDTH_INTERVAL)) return; spin_lock(&wb->list_lock); __wb_update_bandwidth(wb, thresh, bg_thresh, dirty, - bdi_thresh, bdi_dirty, start_time); + wb_thresh, wb_dirty, start_time); spin_unlock(&wb->list_lock); } @@ -1189,7 +1188,7 @@ static unsigned long dirty_poll_interval(unsigned long dirty, } static unsigned long wb_max_pause(struct bdi_writeback *wb, - unsigned long bdi_dirty) + unsigned long wb_dirty) { unsigned long bw = wb->avg_write_bandwidth; unsigned long t; @@ -1201,7 +1200,7 @@ static unsigned long wb_max_pause(struct bdi_writeback *wb, * * 8 serves as the safety ratio. */ - t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); + t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8)); t++; return min_t(unsigned long, t, MAX_PAUSE); @@ -1285,31 +1284,31 @@ static long wb_min_pause(struct bdi_writeback *wb, static inline void wb_dirty_limits(struct bdi_writeback *wb, unsigned long dirty_thresh, unsigned long background_thresh, - unsigned long *bdi_dirty, - unsigned long *bdi_thresh, - unsigned long *bdi_bg_thresh) + unsigned long *wb_dirty, + unsigned long *wb_thresh, + unsigned long *wb_bg_thresh) { unsigned long wb_reclaimable; /* - * bdi_thresh is not treated as some limiting factor as + * wb_thresh is not treated as some limiting factor as * dirty_thresh, due to reasons - * - in JBOD setup, bdi_thresh can fluctuate a lot + * - in JBOD setup, wb_thresh can fluctuate a lot * - in a system with HDD and USB key, the USB key may somehow - * go into state (bdi_dirty >> bdi_thresh) either because - * bdi_dirty starts high, or because bdi_thresh drops low. + * go into state (wb_dirty >> wb_thresh) either because + * wb_dirty starts high, or because wb_thresh drops low. * In this case we don't want to hard throttle the USB key - * dirtiers for 100 seconds until bdi_dirty drops under - * bdi_thresh. Instead the auxiliary bdi control line in + * dirtiers for 100 seconds until wb_dirty drops under + * wb_thresh. Instead the auxiliary wb control line in * wb_position_ratio() will let the dirtier task progress - * at some rate <= (write_bw / 2) for bringing down bdi_dirty. + * at some rate <= (write_bw / 2) for bringing down wb_dirty. */ - *bdi_thresh = wb_dirty_limit(wb, dirty_thresh); + *wb_thresh = wb_dirty_limit(wb, dirty_thresh); - if (bdi_bg_thresh) - *bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh * - background_thresh, - dirty_thresh) : 0; + if (wb_bg_thresh) + *wb_bg_thresh = dirty_thresh ? div_u64((u64)*wb_thresh * + background_thresh, + dirty_thresh) : 0; /* * In order to avoid the stacked BDI deadlock we need @@ -1321,12 +1320,12 @@ static inline void wb_dirty_limits(struct bdi_writeback *wb, * actually dirty; with m+n sitting in the percpu * deltas. */ - if (*bdi_thresh < 2 * wb_stat_error(wb)) { + if (*wb_thresh < 2 * wb_stat_error(wb)) { wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE); - *bdi_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); + *wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK); } else { wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE); - *bdi_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); + *wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK); } } @@ -1360,9 +1359,9 @@ static void balance_dirty_pages(struct address_space *mapping, for (;;) { unsigned long now = jiffies; - unsigned long uninitialized_var(bdi_thresh); + unsigned long uninitialized_var(wb_thresh); unsigned long thresh; - unsigned long uninitialized_var(bdi_dirty); + unsigned long uninitialized_var(wb_dirty); unsigned long dirty; unsigned long bg_thresh; @@ -1380,10 +1379,10 @@ static void balance_dirty_pages(struct address_space *mapping, if (unlikely(strictlimit)) { wb_dirty_limits(wb, dirty_thresh, background_thresh, - &bdi_dirty, &bdi_thresh, &bg_thresh); + &wb_dirty, &wb_thresh, &bg_thresh); - dirty = bdi_dirty; - thresh = bdi_thresh; + dirty = wb_dirty; + thresh = wb_thresh; } else { dirty = nr_dirty; thresh = dirty_thresh; @@ -1393,10 +1392,10 @@ static void balance_dirty_pages(struct address_space *mapping, /* * Throttle it only when the background writeback cannot * catch-up. This avoids (excessively) small writeouts - * when the bdi limits are ramping up in case of !strictlimit. + * when the wb limits are ramping up in case of !strictlimit. * - * In strictlimit case make decision based on the bdi counters - * and limits. Small writeouts when the bdi limits are ramping + * In strictlimit case make decision based on the wb counters + * and limits. Small writeouts when the wb limits are ramping * up are the price we consciously pay for strictlimit-ing. */ if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh)) { @@ -1412,24 +1411,23 @@ static void balance_dirty_pages(struct address_space *mapping, if (!strictlimit) wb_dirty_limits(wb, dirty_thresh, background_thresh, - &bdi_dirty, &bdi_thresh, NULL); + &wb_dirty, &wb_thresh, NULL); - dirty_exceeded = (bdi_dirty > bdi_thresh) && + dirty_exceeded = (wb_dirty > wb_thresh) && ((nr_dirty > dirty_thresh) || strictlimit); if (dirty_exceeded && !wb->dirty_exceeded) wb->dirty_exceeded = 1; wb_update_bandwidth(wb, dirty_thresh, background_thresh, - nr_dirty, bdi_thresh, bdi_dirty, - start_time); + nr_dirty, wb_thresh, wb_dirty, start_time); dirty_ratelimit = wb->dirty_ratelimit; pos_ratio = wb_position_ratio(wb, dirty_thresh, background_thresh, nr_dirty, - bdi_thresh, bdi_dirty); + wb_thresh, wb_dirty); task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >> RATELIMIT_CALC_SHIFT; - max_pause = wb_max_pause(wb, bdi_dirty); + max_pause = wb_max_pause(wb, wb_dirty); min_pause = wb_min_pause(wb, max_pause, task_ratelimit, dirty_ratelimit, &nr_dirtied_pause); @@ -1455,8 +1453,8 @@ static void balance_dirty_pages(struct address_space *mapping, dirty_thresh, background_thresh, nr_dirty, - bdi_thresh, - bdi_dirty, + wb_thresh, + wb_dirty, dirty_ratelimit, task_ratelimit, pages_dirtied, @@ -1484,8 +1482,8 @@ pause: dirty_thresh, background_thresh, nr_dirty, - bdi_thresh, - bdi_dirty, + wb_thresh, + wb_dirty, dirty_ratelimit, task_ratelimit, pages_dirtied, @@ -1508,15 +1506,15 @@ pause: /* * In the case of an unresponding NFS server and the NFS dirty - * pages exceeds dirty_thresh, give the other good bdi's a pipe + * pages exceeds dirty_thresh, give the other good wb's a pipe * to go through, so that tasks on them still remain responsive. * * In theory 1 page is enough to keep the comsumer-producer * pipe going: the flusher cleans 1 page => the task dirties 1 - * more page. However bdi_dirty has accounting errors. So use + * more page. However wb_dirty has accounting errors. So use * the larger and more IO friendly wb_stat_error. */ - if (bdi_dirty <= wb_stat_error(wb)) + if (wb_dirty <= wb_stat_error(wb)) break; if (fatal_signal_pending(current)) |