From: Jeff Layton jlayton@kernel.org
commit df2c0cb7f8e8c83e495260ad86df8c5da947f2a7 upstream.
They both say that the snap_rwsem must be held for write, but I don't see any real reason for it, and it's not currently always called that way.
The lookup is just walking the rbtree, so holding it for read should be fine there. The "get" is bumping the refcount and (possibly) removing it from the empty list. I see no need to hold the snap_rwsem for write for that.
Signed-off-by: Jeff Layton jlayton@kernel.org Reviewed-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ceph/snap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -60,12 +60,12 @@ /* * increase ref count for the realm * - * caller must hold snap_rwsem for write. + * caller must hold snap_rwsem. */ void ceph_get_snap_realm(struct ceph_mds_client *mdsc, struct ceph_snap_realm *realm) { - lockdep_assert_held_write(&mdsc->snap_rwsem); + lockdep_assert_held(&mdsc->snap_rwsem);
dout("get_realm %p %d -> %d\n", realm, atomic_read(&realm->nref), atomic_read(&realm->nref)+1); @@ -139,7 +139,7 @@ static struct ceph_snap_realm *ceph_crea /* * lookup the realm rooted at @ino. * - * caller must hold snap_rwsem for write. + * caller must hold snap_rwsem. */ static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc, u64 ino) @@ -147,7 +147,7 @@ static struct ceph_snap_realm *__lookup_ struct rb_node *n = mdsc->snap_realms.rb_node; struct ceph_snap_realm *r;
- lockdep_assert_held_write(&mdsc->snap_rwsem); + lockdep_assert_held(&mdsc->snap_rwsem);
while (n) { r = rb_entry(n, struct ceph_snap_realm, node);