diff options
| -rw-r--r-- | fs/fs-writeback.c | 5 | ||||
| -rw-r--r-- | include/linux/backing-dev-defs.h | 8 | ||||
| -rw-r--r-- | include/linux/backing-dev.h | 10 | ||||
| -rw-r--r-- | mm/backing-dev.c | 5 | ||||
| -rw-r--r-- | mm/page-writeback.c | 10 |
5 files changed, 25 insertions, 13 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index bbccf68b38db..c98d3923d9a9 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -99,6 +99,7 @@ static bool wb_io_lists_populated(struct bdi_writeback *wb) return false; } else { set_bit(WB_has_dirty_io, &wb->state); + WARN_ON_ONCE(!wb->avg_write_bandwidth); atomic_long_add(wb->avg_write_bandwidth, &wb->bdi->tot_write_bandwidth); return true; @@ -110,8 +111,8 @@ static void wb_io_lists_depopulated(struct bdi_writeback *wb) if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) && list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) { clear_bit(WB_has_dirty_io, &wb->state); - atomic_long_sub(wb->avg_write_bandwidth, - &wb->bdi->tot_write_bandwidth); + WARN_ON_ONCE(atomic_long_sub_return(wb->avg_write_bandwidth, + &wb->bdi->tot_write_bandwidth) < 0); } } diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index d631a61f4023..8c857d723023 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -98,7 +98,7 @@ struct bdi_writeback { unsigned long dirtied_stamp; unsigned long written_stamp; /* pages written at bw_time_stamp */ unsigned long write_bandwidth; /* the estimated write bandwidth */ - unsigned long avg_write_bandwidth; /* further smoothed write bw */ + unsigned long avg_write_bandwidth; /* further smoothed write bw, > 0 */ /* * The base dirty throttle rate, re-calculated on every 200ms. @@ -142,7 +142,11 @@ struct backing_dev_info { unsigned int min_ratio; unsigned int max_ratio, max_prop_frac; - atomic_long_t tot_write_bandwidth; /* sum of active avg_write_bw */ + /* + * Sum of avg_write_bw of wbs with dirty inodes. > 0 if there are + * any dirty wbs, which is depended upon by bdi_has_dirty(). + */ + atomic_long_t tot_write_bandwidth; struct bdi_writeback wb; /* the root writeback info for this bdi */ struct bdi_writeback_congested wb_congested; /* its congested state */ diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 3c8403c012ce..0839e44105bd 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -29,7 +29,6 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages, enum wb_reason reason); void bdi_start_background_writeback(struct backing_dev_info *bdi); void wb_workfn(struct work_struct *work); -bool bdi_has_dirty_io(struct backing_dev_info *bdi); void wb_wakeup_delayed(struct bdi_writeback *wb); extern spinlock_t bdi_lock; @@ -42,6 +41,15 @@ static inline bool wb_has_dirty_io(struct bdi_writeback *wb) return test_bit(WB_has_dirty_io, &wb->state); } +static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi) +{ + /* + * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are + * any dirty wbs. See wb_update_write_bandwidth(). + */ + return atomic_long_read(&bdi->tot_write_bandwidth); +} + static inline void __add_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item, s64 amount) { diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 161ddf12b862..d2f16fc9069a 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -256,11 +256,6 @@ static int __init default_bdi_init(void) } subsys_initcall(default_bdi_init); -bool bdi_has_dirty_io(struct backing_dev_info *bdi) -{ - return wb_has_dirty_io(&bdi->wb); -} - /* * This function is used when the first inode for this wb is marked dirty. It * wakes-up the corresponding bdi thread which should then take care of the diff --git a/mm/page-writeback.c b/mm/page-writeback.c index c95eb24dd652..99b88465096e 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -881,9 +881,13 @@ static void wb_update_write_bandwidth(struct bdi_writeback *wb, avg += (old - avg) >> 3; out: - if (wb_has_dirty_io(wb)) - atomic_long_add(avg - wb->avg_write_bandwidth, - &wb->bdi->tot_write_bandwidth); + /* keep avg > 0 to guarantee that tot > 0 if there are dirty wbs */ + avg = max(avg, 1LU); + if (wb_has_dirty_io(wb)) { + long delta = avg - wb->avg_write_bandwidth; + WARN_ON_ONCE(atomic_long_add_return(delta, + &wb->bdi->tot_write_bandwidth) <= 0); + } wb->write_bandwidth = bw; wb->avg_write_bandwidth = avg; } |