On Thu, Aug 13, 2015 at 07:24:00PM -0400, Tejun Heo wrote:
> Hello, Eryu.
>
> Can you please do the followings?
>
> 1. See if the "writeback: fix syncing of I_DIRTY_TIME inodes" patch
> changes anything.
After applying this patch, I can no longer reproduce the failure.
>
> 2. If not, apply this patch. This patch *should* make the failures go
> away and might print out some error messages along with stack
> trace. Can you please verify that the failures go away with this
> patch and report the kernel messages if any trigger?
And this patch fixed the failure too, and no WARNING no kernel message
triggered.
All my testings are based on 4.2-rc6 kernel (I confirmed rc6 kernel
failed the test first), then applied the first patch, and reverted the
first patch, and applied the second patch.
>
> Thanks a lot.
Thanks for looking into this!
Eryu
>
> Index: work/fs/fs-writeback.c
> ===================================================================
> --- work.orig/fs/fs-writeback.c
> +++ work/fs/fs-writeback.c
> @@ -103,7 +103,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepa
>
> static bool wb_io_lists_populated(struct bdi_writeback *wb)
> {
> - if (wb_has_dirty_io(wb)) {
> + if (test_bit(WB_has_dirty_io, &wb->state)) {
> return false;
> } else {
> set_bit(WB_has_dirty_io, &wb->state);
> @@ -844,14 +844,13 @@ static void bdi_split_work_to_wbs(struct
> struct wb_iter iter;
>
> might_sleep();
> -
> - if (!bdi_has_dirty_io(bdi))
> - return;
> restart:
> rcu_read_lock();
> bdi_for_each_wb(wb, bdi, &iter, next_blkcg_id) {
> - if (!wb_has_dirty_io(wb) ||
> - (skip_if_busy && writeback_in_progress(wb)))
> + /* SYNC_ALL writes out I_DIRTY_TIME too */
> + if (!wb_has_dirty_io(wb) && base_work->sync_mode == WB_SYNC_NONE)
> + continue;
> + if (skip_if_busy && writeback_in_progress(wb))
> continue;
>
> base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages);
> @@ -899,8 +898,7 @@ static void bdi_split_work_to_wbs(struct
> {
> might_sleep();
>
> - if (bdi_has_dirty_io(bdi) &&
> - (!skip_if_busy || !writeback_in_progress(&bdi->wb))) {
> + if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
> base_work->auto_free = 0;
> base_work->single_wait = 0;
> base_work->single_done = 0;
> @@ -2275,8 +2273,8 @@ void sync_inodes_sb(struct super_block *
> };
> struct backing_dev_info *bdi = sb->s_bdi;
>
> - /* Nothing to do? */
> - if (!bdi_has_dirty_io(bdi) || bdi == &noop_backing_dev_info)
> + /* bdi_has_dirty() ignores I_DIRTY_TIME but we can't, always kick wbs */
> + if (bdi == &noop_backing_dev_info)
> return;
> WARN_ON(!rwsem_is_locked(&sb->s_umount));
>
> Index: work/include/linux/backing-dev.h
> ===================================================================
> --- work.orig/include/linux/backing-dev.h
> +++ work/include/linux/backing-dev.h
> @@ -38,7 +38,17 @@ extern struct workqueue_struct *bdi_wq;
>
> static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
> {
> - return test_bit(WB_has_dirty_io, &wb->state);
> + bool ret = test_bit(WB_has_dirty_io, &wb->state);
> +
> + if (!ret && (!list_empty(&wb->b_dirty) || !list_empty(&wb->b_io) ||
> + !list_empty(&wb->b_more_io))) {
> + const char *name = wb->bdi->dev ? dev_name(wb->bdi->dev) : "UNK";
> +
> + pr_err("wb_has_dirty_io: ERR %s has_dirty=%d b_dirty=%d b_io=%d b_more_io=%d\n",
> + name, ret, !list_empty(&wb->b_dirty), !list_empty(&wb->b_io), !list_empty(&wb->b_more_io));
> + WARN_ON(1);
> + }
> + return ret;
> }
>
> static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
> @@ -47,7 +57,18 @@ static inline bool bdi_has_dirty_io(stru
> * @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);
> + bool ret = atomic_long_read(&bdi->tot_write_bandwidth);
> +
> + if (ret != wb_has_dirty_io(&bdi->wb)) {
> + const char *name = bdi->dev ? dev_name(bdi->dev) : "UNK";
> +
> + pr_err("bdi_has_dirty_io: ERR %s tot_write_bw=%ld b_dirty=%d b_io=%d b_more_io=%d\n",
> + name, atomic_long_read(&bdi->tot_write_bandwidth),
> + !list_empty(&bdi->wb.b_dirty), !list_empty(&bdi->wb.b_io), !list_empty(&bdi->wb.b_more_io));
> + WARN_ON(1);
> + }
> +
> + return ret;
> }
>
> static inline void __add_wb_stat(struct bdi_writeback *wb,
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