[PATCH 2/5] writeback: stop periodic/background work on seeing sync works
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From: Wu Fengguang on 29 Jul 2010 08:30 The periodic/background writeback can run forever. So when any sync work is enqueued, increase bdi->sync_works to notify the active non-sync works to exit. Non-sync works queued after sync works won't be affected. Signed-off-by: Wu Fengguang <fengguang.wu(a)intel.com> --- fs/fs-writeback.c | 13 +++++++++++++ include/linux/backing-dev.h | 6 ++++++ mm/backing-dev.c | 1 + 3 files changed, 20 insertions(+) --- linux-next.orig/fs/fs-writeback.c 2010-07-29 17:13:23.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2010-07-29 17:13:49.000000000 +0800 @@ -80,6 +80,8 @@ static void bdi_queue_work(struct backin spin_lock(&bdi->wb_lock); list_add_tail(&work->list, &bdi->work_list); + if (work->for_sync) + atomic_inc(&bdi->wb.sync_works); spin_unlock(&bdi->wb_lock); /* @@ -633,6 +635,14 @@ static long wb_writeback(struct bdi_writ break; /* + * background/periodic works can run forever, need to abort + * on seeing any pending sync work, to prevent livelock it. + */ + if (atomic_read(&wb->sync_works) && + (work->for_background || work->for_kupdate)) + break; + + /* * For background writeout, stop when we are below the * background dirty threshold */ @@ -765,6 +775,9 @@ long wb_do_writeback(struct bdi_writebac wrote += wb_writeback(wb, work); + if (work->for_sync) + atomic_dec(&wb->sync_works); + /* * Notify the caller of completion if this is a synchronous * work item, otherwise just free it. --- linux-next.orig/include/linux/backing-dev.h 2010-07-29 17:13:23.000000000 +0800 +++ linux-next/include/linux/backing-dev.h 2010-07-29 17:13:31.000000000 +0800 @@ -50,6 +50,12 @@ struct bdi_writeback { unsigned long last_old_flush; /* last old data flush */ + /* + * sync works queued, background works shall abort on seeing this, + * to prevent livelocking the sync works + */ + atomic_t sync_works; + struct task_struct *task; /* writeback task */ struct list_head b_dirty; /* dirty inodes */ struct list_head b_io; /* parked for writeback */ --- linux-next.orig/mm/backing-dev.c 2010-07-29 17:13:23.000000000 +0800 +++ linux-next/mm/backing-dev.c 2010-07-29 17:13:31.000000000 +0800 @@ -257,6 +257,7 @@ static void bdi_wb_init(struct bdi_write wb->bdi = bdi; wb->last_old_flush = jiffies; + atomic_set(&wb->sync_works, 0); INIT_LIST_HEAD(&wb->b_dirty); INIT_LIST_HEAD(&wb->b_io); INIT_LIST_HEAD(&wb->b_more_io); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |