nbd: use our own workqueue for recv threads

Since we are in the memory reclaim path we need our recv work to be on a
workqueue that has WQ_MEM_RECLAIM set so we can avoid deadlocks.  Also
set WQ_HIGHPRI since we are in the completion path for IO.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 58296e4427b018e821baf5e4aea54fd5954f6f12..94e76579622d040768f0f7eab95f3a2927f48143 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -91,6 +91,7 @@ static struct dentry *nbd_dbg_dir;
 static unsigned int nbds_max = 16;
 static struct nbd_device *nbd_dev;
 static int max_part;
+static struct workqueue_struct *recv_workqueue;
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
@@ -781,7 +782,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                        INIT_WORK(&args[i].work, recv_work);
                        args[i].nbd = nbd;
                        args[i].index = i;
-                       queue_work(system_long_wq, &args[i].work);
+                       queue_work(recv_workqueue, &args[i].work);
                }
                wait_event_interruptible(nbd->recv_wq,
                                         atomic_read(&nbd->recv_threads) == 0);
@@ -1030,10 +1031,16 @@ static int __init nbd_init(void)
 
        if (nbds_max > 1UL << (MINORBITS - part_shift))
                return -EINVAL;
+       recv_workqueue = alloc_workqueue("knbd-recv",
+                                        WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
+       if (!recv_workqueue)
+               return -ENOMEM;
 
        nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
-       if (!nbd_dev)
+       if (!nbd_dev) {
+               destroy_workqueue(recv_workqueue);
                return -ENOMEM;
+       }
 
        for (i = 0; i < nbds_max; i++) {
                struct request_queue *q;
@@ -1113,6 +1120,7 @@ out:
                put_disk(nbd_dev[i].disk);
        }
        kfree(nbd_dev);
+       destroy_workqueue(recv_workqueue);
        return err;
 }
 
@@ -1132,6 +1140,7 @@ static void __exit nbd_cleanup(void)
                        put_disk(disk);
                }
        }
+       destroy_workqueue(recv_workqueue);
        unregister_blkdev(NBD_MAJOR, "nbd");
        kfree(nbd_dev);
        printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);