writeback: inline allocation failure handling in bdi_alloc_queue_work()

This gets rid of work == NULL in bdi_queue_work() and puts the
OOM handling where it belongs.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f8cd7a9..59b3ee6 100644 (file)
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -149,21 +149,19 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
 
 static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
 {
-       if (work) {
-               work->seen = bdi->wb_mask;
-               BUG_ON(!work->seen);
-               atomic_set(&work->pending, bdi->wb_cnt);
-               BUG_ON(!bdi->wb_cnt);
+       work->seen = bdi->wb_mask;
+       BUG_ON(!work->seen);
+       atomic_set(&work->pending, bdi->wb_cnt);
+       BUG_ON(!bdi->wb_cnt);
 
-               /*
-                * Make sure stores are seen before it appears on the list
-                */
-               smp_mb();
+       /*
+        * Make sure stores are seen before it appears on the list
+        */
+       smp_mb();
 
-               spin_lock(&bdi->wb_lock);
-               list_add_tail_rcu(&work->list, &bdi->work_list);
-               spin_unlock(&bdi->wb_lock);
-       }
+       spin_lock(&bdi->wb_lock);
+       list_add_tail_rcu(&work->list, &bdi->work_list);
+       spin_unlock(&bdi->wb_lock);
 
        /*
         * If the default thread isn't there, make sure we add it. When
@@ -175,14 +173,12 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
                struct bdi_writeback *wb = &bdi->wb;
 
                /*
-                * If we failed allocating the bdi work item, wake up the wb
-                * thread always. As a safety precaution, it'll flush out
-                * everything
+                * End work now if this wb has no dirty IO pending. Otherwise
+                * wakeup the handling thread
                 */
-               if (!wb_has_dirty_io(wb)) {
-                       if (work)
-                               wb_clear_pending(wb, work);
-               } else if (wb->task)
+               if (!wb_has_dirty_io(wb))
+                       wb_clear_pending(wb, work);
+               else if (wb->task)
                        wake_up_process(wb->task);
        }
 }
@@ -202,11 +198,20 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
 {
        struct bdi_work *work;
 
+       /*
+        * This is WB_SYNC_NONE writeback, so if allocation fails just
+        * wakeup the thread for old dirty data writeback
+        */
        work = kmalloc(sizeof(*work), GFP_ATOMIC);
-       if (work)
+       if (work) {
                bdi_work_init(work, wbc);
+               bdi_queue_work(bdi, work);
+       } else {
+               struct bdi_writeback *wb = &bdi->wb;
 
-       bdi_queue_work(bdi, work);
+               if (wb->task)
+                       wake_up_process(wb->task);
+       }
 }
 
 void bdi_start_writeback(struct writeback_control *wbc)