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    SubjectRe: [PATCH 14/49] writeback: s/bdi/wb/ in mm/page-writeback.c
    On Mon 06-04-15 15:58:03, Tejun Heo wrote:
    > Writeback operations will now be per wb (bdi_writeback) instead of
    > bdi. Replace the relevant bdi references in symbol names and comments
    > with wb. This patch is purely cosmetic and doesn't make any
    > functional changes.
    It's good you made things consistent. You can add:
    Reviewed-by: Jan Kara <jack@suse.cz>

    Honza

    >
    > Signed-off-by: Tejun Heo <tj@kernel.org>
    > Cc: Wu Fengguang <fengguang.wu@intel.com>
    > Cc: Jan Kara <jack@suse.cz>
    > Cc: Jens Axboe <axboe@kernel.dk>
    > ---
    > mm/page-writeback.c | 270 ++++++++++++++++++++++++++--------------------------
    > 1 file changed, 134 insertions(+), 136 deletions(-)
    >
    > diff --git a/mm/page-writeback.c b/mm/page-writeback.c
    > index 29fb4f3..c615a15 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))
    > --
    > 2.1.0
    >
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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