Messages in this thread Patch in this message | | | Date | Tue, 09 Nov 2010 07:09:19 +0800 | From | Wu Fengguang <> | Subject | [PATCH 3/5] writeback: stop background/kupdate works from livelocking other works |
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From: Jan Kara <jack@suse.cz>
Background writeback are easily livelockable (from a definition of their target). This is inconvenient because it can make sync(1) stall forever waiting on its queued work to be finished. Generally, when a flusher thread has some work queued, someone submitted the work to achieve a goal more specific than what background writeback does. So it makes sense to give it a priority over a generic page cleaning.
Thus we interrupt background writeback if there is some other work to do. We return to the background writeback after completing all the queued work.
Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> --- fs/fs-writeback.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- linux-next.orig/fs/fs-writeback.c 2010-11-07 21:56:42.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2010-11-07 22:00:51.000000000 +0800 @@ -651,6 +651,15 @@ static long wb_writeback(struct bdi_writ break; /* + * Background writeout and kupdate-style writeback are + * easily livelockable. Stop them if there is other work + * to do so that e.g. sync can proceed. + */ + if ((work->for_background || work->for_kupdate) && + !list_empty(&wb->bdi->work_list)) + break; + + /* * For background writeout, stop when we are below the * background dirty threshold */
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