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author | Alex Elder <elder@dreamhost.com> | 2012-01-29 13:57:43 -0600 |
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committer | Sage Weil <sage@newdream.net> | 2012-02-02 12:56:59 -0800 |
commit | d23a4b3fd6ef70b80411b39b8c8bc548a219ce70 (patch) | |
tree | f42dbc4c8544acce987e35df5b3002f1def54cff /fs/ceph | |
parent | 97bb59a03dd6767fcc00be09b0c6d9e5294eeea6 (diff) | |
download | linux-stable-d23a4b3fd6ef70b80411b39b8c8bc548a219ce70.tar.gz linux-stable-d23a4b3fd6ef70b80411b39b8c8bc548a219ce70.tar.bz2 linux-stable-d23a4b3fd6ef70b80411b39b8c8bc548a219ce70.zip |
rbd: fix safety of rbd_put_client()
The rbd_client structure uses a kref to arrange for cleaning up and
freeing an instance when its last reference is dropped. The cleanup
routine is rbd_client_release(), and one of the things it does is
delete the rbd_client from rbd_client_list. It acquires node_lock
to do so, but the way it is done is still not safe.
The problem is that when attempting to reuse an existing rbd_client,
the structure found might already be in the process of getting
destroyed and cleaned up.
Here's the scenario, with "CLIENT" representing an existing
rbd_client that's involved in the race:
Thread on CPU A | Thread on CPU B
--------------- | ---------------
rbd_put_client(CLIENT) | rbd_get_client()
kref_put() | (acquires node_lock)
kref->refcount becomes 0 | __rbd_client_find() returns CLIENT
calls rbd_client_release() | kref_get(&CLIENT->kref);
| (releases node_lock)
(acquires node_lock) |
deletes CLIENT from list | ...and starts using CLIENT...
(releases node_lock) |
and frees CLIENT | <-- but CLIENT gets freed here
Fix this by having rbd_put_client() acquire node_lock. The result
could still be improved, but at least it avoids this problem.
Signed-off-by: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>
Diffstat (limited to 'fs/ceph')
0 files changed, 0 insertions, 0 deletions