e79729123f63 ("writeback: don't issue wb_writeback_work if clean")
updated writeback path to avoid kicking writeback work items if there
are no inodes to be written out; unfortunately, the avoidance logic
was too aggressive and broke sync_inodes_sb().
* sync_inodes_sb() must write out I_DIRTY_TIME inodes but I_DIRTY_TIME
inodes dont't contribute to bdi/wb_has_dirty_io() tests and were
being skipped over.
* inodes are taken off wb->b_dirty/io/more_io lists after writeback
starts on them. sync_inodes_sb() skipping wait_sb_inodes() when
bdi_has_dirty_io() breaks it by making it return while writebacks
are in-flight.
This patch fixes the breakages by
* Removing bdi_has_dirty_io() shortcut from bdi_split_work_to_wbs().
The callers are already testing the condition.
* Removing bdi_has_dirty_io() shortcut from sync_inodes_sb() so that
it always calls into bdi_split_work_to_wbs() and wait_sb_inodes().
* Making bdi_split_work_to_wbs() consider the b_dirty_time list for
WB_SYNC_ALL writebacks.
Kudos to Eryu, Dave and Jan for tracking down the issue.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Fixes: e79729123f63 ("writeback: don't issue wb_writeback_work if clean")
Link: http://lkml.kernel.org/g/20150812101204.GE17933@xxxxxxxxxxxxxxxxxxxxxxxxxx
Reported-and-bisected-by: Eryu Guan <eguan@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxxx>
Cc: Ted Ts'o <tytso@xxxxxxxxxx>
---
fs/fs-writeback.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -844,14 +844,15 @@ 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 ||
+ list_empty(&wb->b_dirty_time)))
+ continue;
+ if (skip_if_busy && writeback_in_progress(wb))
continue;
base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages);
@@ -899,8 +900,7 @@ 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 +2275,12 @@ 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)
+ /*
+ * Can't skip on !bdi_has_dirty() because we should wait for !dirty
+ * inodes under writeback and I_DIRTY_TIME inodes ignored by
+ * bdi_has_dirty() need to be written out too.
+ */
+ if (bdi == &noop_backing_dev_info)
return;
WARN_ON(!rwsem_is_locked(&sb->s_umount));
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