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>

1 files changed, 27 insertions, 22 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f8cd7a97f5b7..59b3ee63b624 100644
--- 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)