Reviewed-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
Alex Elder <elder@xxxxxxxxxxx> wrote:
>When an rbd device is first getting mapped, its device registration
>is protected the control mutex. There is no need to do that though,
>because the device has already been assigned an id that's guaranteed
>to be unique.
>
>An unmap of an rbd device won't proceed if the device has a non-zero
>open count or is already being unmapped. So there's no need to hold
>the control mutex in that case either.
>
>Finally, an rbd device can't be opened if it is being removed, and
>it won't go away if there is a non-zero open count. So here too
>there's no need to hold the control mutex while getting or putting a
>reference to an rbd device's Linux device structure.
>
>Drop the mutex calls in these cases.
>
>Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
>---
> drivers/block/rbd.c | 17 ++---------------
> 1 file changed, 2 insertions(+), 15 deletions(-)
>
>diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
>index 380940d..9c81a5c 100644
>--- a/drivers/block/rbd.c
>+++ b/drivers/block/rbd.c
>@@ -489,10 +489,8 @@ static int rbd_open(struct block_device *bdev,
>fmode_t mode)
> if (removing)
> return -ENOENT;
>
>- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
> (void) get_device(&rbd_dev->dev);
> set_device_ro(bdev, rbd_dev->mapping.read_only);
>- mutex_unlock(&ctl_mutex);
>
> return 0;
> }
>@@ -507,9 +505,7 @@ static int rbd_release(struct gendisk *disk,
>fmode_t
>mode)
> spin_unlock_irq(&rbd_dev->lock);
> rbd_assert(open_count_before > 0);
>
>- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
> put_device(&rbd_dev->dev);
>- mutex_unlock(&ctl_mutex);
>
> return 0;
> }
>@@ -4348,8 +4344,6 @@ static int rbd_bus_add_dev(struct rbd_device
>*rbd_dev)
> struct device *dev;
> int ret;
>
>- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
>-
> dev = &rbd_dev->dev;
> dev->bus = &rbd_bus_type;
> dev->type = &rbd_device_type;
>@@ -4358,8 +4352,6 @@ static int rbd_bus_add_dev(struct rbd_device
>*rbd_dev)
> dev_set_name(dev, "%d", rbd_dev->dev_id);
> ret = device_register(dev);
>
>- mutex_unlock(&ctl_mutex);
>-
> return ret;
> }
>
>@@ -5165,8 +5157,6 @@ static ssize_t rbd_remove(struct bus_type *bus,
> if (dev_id != ul)
> return -EINVAL;
>
>- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
>-
> ret = -ENOENT;
> spin_lock(&rbd_dev_list_lock);
> list_for_each(tmp, &rbd_dev_list) {
>@@ -5187,7 +5177,7 @@ static ssize_t rbd_remove(struct bus_type *bus,
> }
> spin_unlock(&rbd_dev_list_lock);
> if (ret < 0 || already)
>- goto done;
>+ return ret;
>
> rbd_bus_del_dev(rbd_dev);
> ret = rbd_dev_header_watch_sync(rbd_dev, false);
>@@ -5195,11 +5185,8 @@ static ssize_t rbd_remove(struct bus_type *bus,
> rbd_warn(rbd_dev, "failed to cancel watch event (%d)\n", ret);
> rbd_dev_image_release(rbd_dev);
> module_put(THIS_MODULE);
>- ret = count;
>-done:
>- mutex_unlock(&ctl_mutex);
>
>- return ret;
>+ return count;
> }
>
> /*
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
