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author | Derek Basehore <dbasehore@chromium.org> | 2014-04-03 14:46:22 -0700 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-26 17:19:05 -0700 |
commit | 67001f3a0bc4373452a2a3241e4b038bdc796cda (patch) | |
tree | b889fa5cd5a4c03cda7367e36f00614aecb4e53e /fs/fs-writeback.c | |
parent | e5cf61cfe83f493f118d93853d4bad367367e2b8 (diff) | |
download | lwn-67001f3a0bc4373452a2a3241e4b038bdc796cda.tar.gz lwn-67001f3a0bc4373452a2a3241e4b038bdc796cda.zip |
backing_dev: fix hung task on sync
commit 6ca738d60c563d5c6cf6253ee4b8e76fa77b2b9e upstream.
bdi_wakeup_thread_delayed() used the mod_delayed_work() function 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 caused by commit
839a8e8660b6 ("writeback: replace custom worker pool implementation with
unbound workqueue").
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.
We fix the problem by using queue_delayed_work() when we want to
schedule writeback sometime in future. This function doesn't change the
timer if it is already armed.
For the same reason, we also change 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.
[jack@suse.cz: update changelog, add comment, use bdi_wakeup_thread_delayed()]
Signed-off-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zento.linux.org.uk>
Reviewed-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Derek Basehore <dbasehore@chromium.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Benson Leung <bleung@chromium.org>
Cc: Sonny Rao <sonnyrao@chromium.org>
Cc: Luigi Semenzato <semenzato@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/fs-writeback.c')
-rw-r--r-- | fs/fs-writeback.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index d754e3cf99a8..6788fe0c9761 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1039,10 +1039,10 @@ void bdi_writeback_workfn(struct work_struct *work) trace_writeback_pages_written(pages_written); } - if (!list_empty(&bdi->work_list) || - (wb_has_dirty_io(wb) && dirty_writeback_interval)) - queue_delayed_work(bdi_wq, &wb->dwork, - msecs_to_jiffies(dirty_writeback_interval * 10)); + if (!list_empty(&bdi->work_list)) + mod_delayed_work(bdi_wq, &wb->dwork, 0); + else if (wb_has_dirty_io(wb) && dirty_writeback_interval) + bdi_wakeup_thread_delayed(bdi); current->flags &= ~PF_SWAPWRITE; } |