Subject: + backing_dev-fix-hung-task-on-sync.patch added to -mm tree
To: dbasehore@xxxxxxxxxxxx,axboe@xxxxxxxxx,bleung@xxxxxxxxxxxx,darrick.wong@xxxxxxxxxx,david@xxxxxxxxxxxxx,gregkh@xxxxxxxxxxxxxxxxxxx,jack@xxxxxxx,keescook@xxxxxxxxxxxx,semenzato@xxxxxxxxxxxx,sonnyrao@xxxxxxxxxxxx,stable@xxxxxxxxxxxxxxx,tj@xxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 18 Feb 2014 12:29:08 -0800
The patch titled
Subject: backing_dev: fix hung task on sync
has been added to the -mm tree. Its filename is
backing_dev-fix-hung-task-on-sync.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/backing_dev-fix-hung-task-on-sync.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/backing_dev-fix-hung-task-on-sync.patch
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From: Derek Basehore <dbasehore@xxxxxxxxxxxx>
Subject: backing_dev: fix hung task on sync
bdi_wakeup_thread_delayed() used mod_delayed_work() to schedule work to
writeback dirty inodes. The problem with this is that it can delay work
that is scheduled for immediate execution, such as the work from
sync_inodes_sb(). This can happen since mod_delayed_work can now steal
work from a work_queue. This fixes the problem by using
queue_delayed_work instead. This is a regression from the move to the bdi
workqueue design.
The reason that this causes a problem is that laptop-mode will change the
delay, dirty_writeback_centisecs, to 60000 (10 minutes) by default. In
the case that bdi_wakeup_thread_delayed races with sync_inodes_sb, sync
will be stopped for 10 minutes and trigger a hung task. Even if
dirty_writeback_centisecs is not long enough to cause a hung task, we
still don't want to delay sync for that long.
For the same reason, this also changes bdi_writeback_workfn to immediately
queue the work again in the case that the work_list is not empty. The
same problem can happen if the sync work is run on the rescue worker.
Signed-off-by: Derek Basehore <dbasehore@xxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Cc: Derek Basehore <dbasehore@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Benson Leung <bleung@xxxxxxxxxxxx>
Cc: Sonny Rao <sonnyrao@xxxxxxxxxxxx>
Cc: Luigi Semenzato <semenzato@xxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 5 +++--
mm/backing-dev.c | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)
diff -puN fs/fs-writeback.c~backing_dev-fix-hung-task-on-sync fs/fs-writeback.c
--- a/fs/fs-writeback.c~backing_dev-fix-hung-task-on-sync
+++ a/fs/fs-writeback.c
@@ -1047,8 +1047,9 @@ void bdi_writeback_workfn(struct work_st
trace_writeback_pages_written(pages_written);
}
- if (!list_empty(&bdi->work_list) ||
- (wb_has_dirty_io(wb) && dirty_writeback_interval))
+ if (!list_empty(&bdi->work_list))
+ mod_delayed_work(bdi_wq, &wb->dwork, 0);
+ else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
queue_delayed_work(bdi_wq, &wb->dwork,
msecs_to_jiffies(dirty_writeback_interval * 10));
diff -puN mm/backing-dev.c~backing_dev-fix-hung-task-on-sync mm/backing-dev.c
--- a/mm/backing-dev.c~backing_dev-fix-hung-task-on-sync
+++ a/mm/backing-dev.c
@@ -294,7 +294,7 @@ void bdi_wakeup_thread_delayed(struct ba
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
- mod_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
+ queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
}
/*
_
Patches currently in -mm which might be from dbasehore@xxxxxxxxxxxx are
backing_dev-fix-hung-task-on-sync.patch
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