[ 162/171] rbd: do not allow remove of mounted-on image

Greg Kroah-Hartman
2013-01-15T22:53:49Z

From: Alex Elder <elder@inktank.com>

There is no check in rbd_remove() to see if anybody holds open the
image being removed. That's not cool.

Add a simple open count that goes up and down with opens and closes
(releases) of the device, and don't allow an rbd image to be removed
if the count is non-zero.

Protect the updates of the open count value with ctl_mutex to ensure
the underlying rbd device doesn't get removed while concurrently
being opened.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
(based on commit 42382b709bd1d143b9f0fa93e0a3a1f2f4210707)
---
drivers/block/rbd.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -189,6 +189,7 @@ struct rbd_device {

/* sysfs related */
struct device dev;
+ unsigned long open_count;
};

static DEFINE_MUTEX(ctl_mutex); /* Serialize open/close/setup/teardown */
@@ -249,8 +250,11 @@ static int rbd_open(struct block_device
if ((mode & FMODE_WRITE) && rbd_dev->read_only)
return -EROFS;

+ mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
rbd_get_dev(rbd_dev);
set_device_ro(bdev, rbd_dev->read_only);
+ rbd_dev->open_count++;
+ mutex_unlock(&ctl_mutex);

return 0;
}
@@ -259,7 +263,11 @@ static int rbd_release(struct gendisk *d
{
struct rbd_device *rbd_dev = disk->private_data;

+ mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+ BUG_ON(!rbd_dev->open_count);
+ rbd_dev->open_count--;
rbd_put_dev(rbd_dev);
+ mutex_unlock(&ctl_mutex);

return 0;
}
@@ -2448,6 +2456,11 @@ static ssize_t rbd_remove(struct bus_typ
goto done;
}

+ if (rbd_dev->open_count) {
+ ret = -EBUSY;
+ goto done;
+ }
+
__rbd_remove_all_snaps(rbd_dev);
rbd_bus_del_dev(rbd_dev);