The problem is, redirty_tail() may update i_dirtied_when and result in 30s max delay. If redirty_tail() is called often enough, some inode may even be delayed for ever. So introduce the b_more_io_wait queue to park inodes that for some reason cannot be synced immediately. The inodes will be sent to b_io at the next b_io refill time, however won't be busy retried as b_more_io: when the redirtied inodes are all in b_more_io_wait, wb_writeback() will see empty b_more_io and hence break out of the loop. This would be the new data flow after converting all redirty_tail() calls to requeue_io_wait(): b_dirty --> b_io --> b_more_io/b_more_io_wait --+ ^ | | | +----------------------------------+ Cc: Jan Kara Cc: Dave Chinner Signed-off-by: Wu Fengguang --- fs/fs-writeback.c | 16 ++++++++++++++++ include/linux/backing-dev.h | 8 +++++--- mm/backing-dev.c | 10 ++++++++-- 3 files changed, 29 insertions(+), 5 deletions(-) --- linux-next.orig/fs/fs-writeback.c 2011-10-20 23:13:48.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2011-10-20 23:19:12.000000000 +0800 @@ -234,6 +234,21 @@ static void requeue_io(struct inode *ino list_move(&inode->i_wb_list, &wb->b_more_io); } +/* + * The inode should be retried in an opportunistic way. + * + * The only difference between b_more_io and b_more_io_wait is: + * wb_writeback() won't quit as long as b_more_io is not empty. When + * wb_writeback() quit on empty b_more_io and non-empty b_more_io_wait, + * the kupdate work will wakeup more frequently to retry the inodes in + * b_more_io_wait. + */ +static void requeue_io_wait(struct inode *inode, struct bdi_writeback *wb) +{ + assert_spin_locked(&wb->list_lock); + list_move(&inode->i_wb_list, &wb->b_more_io_wait); +} + static void inode_sync_complete(struct inode *inode) { /* @@ -321,6 +336,7 @@ static void queue_io(struct bdi_writebac int moved; assert_spin_locked(&wb->list_lock); list_splice_init(&wb->b_more_io, &wb->b_io); + list_splice_init(&wb->b_more_io_wait, &wb->b_io); moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work); trace_writeback_queue_io(wb, work, moved); } --- linux-next.orig/include/linux/backing-dev.h 2011-10-20 23:13:48.000000000 +0800 +++ linux-next/include/linux/backing-dev.h 2011-10-20 23:13:50.000000000 +0800 @@ -59,6 +59,7 @@ struct bdi_writeback { struct list_head b_dirty; /* dirty inodes */ struct list_head b_io; /* parked for writeback */ struct list_head b_more_io; /* parked for more writeback */ + struct list_head b_more_io_wait;/* opportunistic retry io */ spinlock_t list_lock; /* protects the b_* lists */ }; @@ -133,9 +134,10 @@ extern struct list_head bdi_pending_list static inline int wb_has_dirty_io(struct bdi_writeback *wb) { - return !list_empty(&wb->b_dirty) || - !list_empty(&wb->b_io) || - !list_empty(&wb->b_more_io); + return !list_empty(&wb->b_dirty) || + !list_empty(&wb->b_io) || + !list_empty(&wb->b_more_io) || + !list_empty(&wb->b_more_io_wait); } static inline void __add_bdi_stat(struct backing_dev_info *bdi, --- linux-next.orig/mm/backing-dev.c 2011-10-20 23:13:48.000000000 +0800 +++ linux-next/mm/backing-dev.c 2011-10-20 23:13:50.000000000 +0800 @@ -74,10 +74,10 @@ static int bdi_debug_stats_show(struct s unsigned long background_thresh; unsigned long dirty_thresh; unsigned long bdi_thresh; - unsigned long nr_dirty, nr_io, nr_more_io; + unsigned long nr_dirty, nr_io, nr_more_io, nr_more_io_wait; struct inode *inode; - nr_dirty = nr_io = nr_more_io = 0; + nr_dirty = nr_io = nr_more_io = nr_more_io_wait = 0; spin_lock(&wb->list_lock); list_for_each_entry(inode, &wb->b_dirty, i_wb_list) nr_dirty++; @@ -85,6 +85,8 @@ static int bdi_debug_stats_show(struct s nr_io++; list_for_each_entry(inode, &wb->b_more_io, i_wb_list) nr_more_io++; + list_for_each_entry(inode, &wb->b_more_io_wait, i_wb_list) + nr_more_io_wait++; spin_unlock(&wb->list_lock); global_dirty_limits(&background_thresh, &dirty_thresh); @@ -103,6 +105,7 @@ static int bdi_debug_stats_show(struct s "b_dirty: %10lu\n" "b_io: %10lu\n" "b_more_io: %10lu\n" + "b_more_io_wait: %10lu\n" "bdi_list: %10u\n" "state: %10lx\n", (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)), @@ -116,6 +119,7 @@ static int bdi_debug_stats_show(struct s nr_dirty, nr_io, nr_more_io, + nr_more_io_wait, !list_empty(&bdi->bdi_list), bdi->state); #undef K @@ -651,6 +655,7 @@ static void bdi_wb_init(struct bdi_write INIT_LIST_HEAD(&wb->b_dirty); INIT_LIST_HEAD(&wb->b_io); INIT_LIST_HEAD(&wb->b_more_io); + INIT_LIST_HEAD(&wb->b_more_io_wait); spin_lock_init(&wb->list_lock); setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi); } @@ -718,6 +723,7 @@ void bdi_destroy(struct backing_dev_info list_splice(&bdi->wb.b_dirty, &dst->b_dirty); list_splice(&bdi->wb.b_io, &dst->b_io); list_splice(&bdi->wb.b_more_io, &dst->b_more_io); + list_splice(&bdi->wb.b_more_io_wait, &dst->b_more_io_wait); spin_unlock(&bdi->wb.list_lock); spin_unlock(&dst->list_lock); } -- 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/