block: loop: don't hold lo_ctl_mutex in lo_open

[linux-2.6-block.git] / drivers / block / loop.c

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ae3fcb4199e9b7d85d2475d40ab4f209258a1cc5..b3e294e529ecc11ac8b982f9859e655eb0bc0783 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -86,8 +86,6 @@ static DEFINE_MUTEX(loop_index_mutex);
 static int max_part;
 static int part_shift;
 
-static struct workqueue_struct *loop_wq;
-
 static int transfer_xor(struct loop_device *lo, int cmd,
                        struct page *raw_page, unsigned raw_off,
                        struct page *loop_page, unsigned loop_off,
@@ -725,6 +723,12 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
        size = get_loop_size(lo, file);
        if ((loff_t)(sector_t)size != size)
                goto out_putf;
+       error = -ENOMEM;
+       lo->wq = alloc_workqueue("kloopd%d",
+                       WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16,
+                       lo->lo_number);
+       if (!lo->wq)
+               goto out_putf;
 
        error = 0;
 
@@ -827,7 +831,7 @@ static int loop_clr_fd(struct loop_device *lo)
         * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
         * command to fail with EBUSY.
         */
-       if (lo->lo_refcnt > 1) {
+       if (atomic_read(&lo->lo_refcnt) > 1) {
                lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
                mutex_unlock(&lo->lo_ctl_mutex);
                return 0;
@@ -836,6 +840,9 @@ static int loop_clr_fd(struct loop_device *lo)
        if (filp == NULL)
                return -EINVAL;
 
+       /* freeze request queue during the transition */
+       blk_mq_freeze_queue(lo->lo_queue);
+
        spin_lock_irq(&lo->lo_lock);
        lo->lo_state = Lo_rundown;
        lo->lo_backing_file = NULL;
@@ -867,11 +874,15 @@ static int loop_clr_fd(struct loop_device *lo)
        lo->lo_state = Lo_unbound;
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
+       blk_mq_unfreeze_queue(lo->lo_queue);
+
        if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
                ioctl_by_bdev(bdev, BLKRRPART, 0);
        lo->lo_flags = 0;
        if (!part_shift)
                lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
+       destroy_workqueue(lo->wq);
+       lo->wq = NULL;
        mutex_unlock(&lo->lo_ctl_mutex);
        /*
         * Need not hold lo_ctl_mutex to fput backing file.
@@ -1324,9 +1335,7 @@ static int lo_open(struct block_device *bdev, fmode_t mode)
                goto out;
        }
 
-       mutex_lock(&lo->lo_ctl_mutex);
-       lo->lo_refcnt++;
-       mutex_unlock(&lo->lo_ctl_mutex);
+       atomic_inc(&lo->lo_refcnt);
 out:
        mutex_unlock(&loop_index_mutex);
        return err;
@@ -1337,11 +1346,10 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
        struct loop_device *lo = disk->private_data;
        int err;
 
-       mutex_lock(&lo->lo_ctl_mutex);
-
-       if (--lo->lo_refcnt)
-               goto out;
+       if (atomic_dec_return(&lo->lo_refcnt))
+               return;
 
+       mutex_lock(&lo->lo_ctl_mutex);
        if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
                /*
                 * In autoclear mode, stop the loop thread
@@ -1425,9 +1433,13 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
                const struct blk_mq_queue_data *bd)
 {
        struct loop_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
+       struct loop_device *lo = cmd->rq->q->queuedata;
 
        blk_mq_start_request(bd->rq);
 
+       if (lo->lo_state != Lo_bound)
+               return -EIO;
+
        if (cmd->rq->cmd_flags & REQ_WRITE) {
                struct loop_device *lo = cmd->rq->q->queuedata;
                bool need_sched = true;
@@ -1441,9 +1453,9 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
                spin_unlock_irq(&lo->lo_lock);
 
                if (need_sched)
-                       queue_work(loop_wq, &lo->write_work);
+                       queue_work(lo->wq, &lo->write_work);
        } else {
-               queue_work(loop_wq, &cmd->read_work);
+               queue_work(lo->wq, &cmd->read_work);
        }
 
        return BLK_MQ_RQ_QUEUE_OK;
@@ -1455,9 +1467,6 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
        struct loop_device *lo = cmd->rq->q->queuedata;
        int ret = -EIO;
 
-       if (lo->lo_state != Lo_bound)
-               goto failed;
-
        if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY))
                goto failed;
 
@@ -1594,6 +1603,7 @@ static int loop_add(struct loop_device **l, int i)
                disk->flags |= GENHD_FL_NO_PART_SCAN;
        disk->flags |= GENHD_FL_EXT_DEVT;
        mutex_init(&lo->lo_ctl_mutex);
+       atomic_set(&lo->lo_refcnt, 0);
        lo->lo_number           = i;
        spin_lock_init(&lo->lo_lock);
        disk->major             = LOOP_MAJOR;
@@ -1711,7 +1721,7 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
                        mutex_unlock(&lo->lo_ctl_mutex);
                        break;
                }
-               if (lo->lo_refcnt > 0) {
+               if (atomic_read(&lo->lo_refcnt) > 0) {
                        ret = -EBUSY;
                        mutex_unlock(&lo->lo_ctl_mutex);
                        break;
@@ -1806,13 +1816,6 @@ static int __init loop_init(void)
                goto misc_out;
        }
 
-       loop_wq = alloc_workqueue("kloopd",
-                       WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0);
-       if (!loop_wq) {
-               err = -ENOMEM;
-               goto misc_out;
-       }
-
        blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
                                  THIS_MODULE, loop_probe, NULL, NULL);
 
@@ -1850,8 +1853,6 @@ static void __exit loop_exit(void)
        blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
        unregister_blkdev(LOOP_MAJOR, "loop");
 
-       destroy_workqueue(loop_wq);
-
        misc_deregister(&loop_misc);
 }