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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2016-08-04 21:36:05 +0300
committerJens Axboe <axboe@fb.com>2016-08-09 19:58:06 -0600
commit51350ea0d7f355dfc03deb343a665802d3d5cbba (patch)
tree775b636093a744285f6226337a16d99020d1ee6d
parentd3f422c8d58b2f0d68a51db88389a715dc10b4d2 (diff)
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mm, writeback: flush plugged IO in wakeup_flusher_threads()
I've found funny live-lock between raid10 barriers during resync and memory controller hard limits. Inside mpage_readpages() task holds on to its plug bio which blocks the barrier in raid10. Its memory cgroup have no free memory thus the task goes into reclaimer but all reclaimable pages are dirty and cannot be written because raid10 is rebuilding and stuck on the barrier. Common flush of such IO in schedule() never happens, because the caller doesn't go to sleep. Lock is 'live' because changing memory limit or killing tasks which holds that stuck bio unblock whole progress. That was what happened in 3.18.x but I see no difference in upstream logic. Theoretically this might happen even without memory cgroup. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--fs/fs-writeback.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4d09d4441e3e..05713a5da083 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1949,6 +1949,12 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
{
struct backing_dev_info *bdi;
+ /*
+ * If we are expecting writeback progress we must submit plugged IO.
+ */
+ if (blk_needs_flush_plug(current))
+ blk_schedule_flush_plug(current);
+
if (!nr_pages)
nr_pages = get_nr_dirty_pages();