rbd: set removing flag while holding list lock

When unmapping a device, its id is supplied, and that is used to
look up which rbd device should be unmapped.  Looking up the
device involves searching the rbd device list while holding
a spinlock that protects access to that list.

Currently all of this is done under protection of the control lock,
but that protection is going away soon.  To ensure the rbd_dev is
still valid (still on the list) while setting its REMOVING flag, do
so while still holding the list lock.  To do so, get rid of
__rbd_get_dev(), and open code what it did in the one place it
was used.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 22 insertions, 31 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index fd2795d1136a..9eead4879c90 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -5090,23 +5090,6 @@ err_out_module:
         return (ssize_t)rc;
 }
 
-static struct rbd_device *__rbd_get_dev(unsigned long dev_id)
-{
-        struct list_head *tmp;
-        struct rbd_device *rbd_dev;
-
-        spin_lock(&rbd_dev_list_lock);
-        list_for_each(tmp, &rbd_dev_list) {
-                rbd_dev = list_entry(tmp, struct rbd_device, node);
-                if (rbd_dev->dev_id == dev_id) {
-                        spin_unlock(&rbd_dev_list_lock);
-                        return rbd_dev;
-                }
-        }
-        spin_unlock(&rbd_dev_list_lock);
-        return NULL;
-}
-
 static void rbd_dev_device_release(struct device *dev)
 {
         struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
@@ -5151,7 +5134,8 @@ static ssize_t rbd_remove(struct bus_type *bus,
                           size_t count)
 {
         struct rbd_device *rbd_dev = NULL;
-        int target_id;
+        struct list_head *tmp;
+        int dev_id;
         unsigned long ul;
         int ret;
 
@@ -5160,26 +5144,33 @@ static ssize_t rbd_remove(struct bus_type *bus,
                 return ret;
 
         /* convert to int; abort if we lost anything in the conversion */
-        target_id = (int) ul;
-        if (target_id != ul)
+        dev_id = (int)ul;
+        if (dev_id != ul)
                 return -EINVAL;
 
         mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 
-        rbd_dev = __rbd_get_dev(target_id);
-        if (!rbd_dev) {
-                ret = -ENOENT;
-                goto done;
+        ret = -ENOENT;
+        spin_lock(&rbd_dev_list_lock);
+        list_for_each(tmp, &rbd_dev_list) {
+                rbd_dev = list_entry(tmp, struct rbd_device, node);
+                if (rbd_dev->dev_id == dev_id) {
+                        ret = 0;
+                        break;
+                }
         }
-
-        spin_lock_irq(&rbd_dev->lock);
-        if (rbd_dev->open_count)
-                ret = -EBUSY;
-        else
-                set_bit(RBD_DEV_FLAG_REMOVING, &rbd_dev->flags);
-        spin_unlock_irq(&rbd_dev->lock);
+        if (!ret) {
+                spin_lock_irq(&rbd_dev->lock);
+                if (rbd_dev->open_count)
+                        ret = -EBUSY;
+                else
+                        set_bit(RBD_DEV_FLAG_REMOVING, &rbd_dev->flags);
+                spin_unlock_irq(&rbd_dev->lock);
+        }
+        spin_unlock(&rbd_dev_list_lock);
         if (ret < 0)
                 goto done;
+
         rbd_bus_del_dev(rbd_dev);
         ret = rbd_dev_header_watch_sync(rbd_dev, false);
         if (ret)