Background writeback and kupdate-style 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, if someone has a particular requirement for writeback he needs, it makes sense to give it preference over a generic background dirty page cleaning. As soon as that work is done, flusher thread will return back to background cleaning if it is needed. So lets just interrupt background and kupdate writeback if there is some other work to do to fix the livelocking problem. CC: hch@xxxxxxxxxxxxx Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> --- fs/fs-writeback.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index d5be169..542471e 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -633,6 +633,14 @@ static long wb_writeback(struct bdi_writeback *wb, 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 */ -- 1.6.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
