diff options
Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 424577152eb5..399619c97567 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -53,6 +53,7 @@ struct wb_writeback_work { unsigned int for_background:1; unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ unsigned int auto_free:1; /* free on completion */ + unsigned int start_all:1; /* nr_pages == 0 (all) writeback */ enum wb_reason reason; /* why was writeback initiated? */ struct list_head list; /* pending work list */ @@ -952,12 +953,27 @@ static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason) return; /* + * All callers of this function want to start writeback of all + * dirty pages. Places like vmscan can call this at a very + * high frequency, causing pointless allocations of tons of + * work items and keeping the flusher threads busy retrieving + * that work. Ensure that we only allow one of them pending and + * inflight at the time. It doesn't matter if we race a little + * bit on this, so use the faster separate test/set bit variants. + */ + if (test_bit(WB_start_all, &wb->state)) + return; + + set_bit(WB_start_all, &wb->state); + + /* * This is WB_SYNC_NONE writeback, so if allocation fails just * wakeup the thread for old dirty data writeback */ work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN); if (!work) { + clear_bit(WB_start_all, &wb->state); trace_writeback_nowork(wb); wb_wakeup(wb); return; @@ -968,6 +984,7 @@ static void wb_start_writeback(struct bdi_writeback *wb, enum wb_reason reason) work->range_cyclic = 1; work->reason = reason; work->auto_free = 1; + work->start_all = 1; wb_queue_work(wb, work); } @@ -1821,6 +1838,14 @@ static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb) list_del_init(&work->list); } spin_unlock_bh(&wb->work_lock); + + /* + * Once we start processing a work item that had !nr_pages, + * clear the wb state bit for that so we can allow more. + */ + if (work && work->start_all) + clear_bit(WB_start_all, &wb->state); + return work; } |