Commit 7f47f7f3 authored by Niels Dossche's avatar Niels Dossche Committed by Ilya Dryomov
Browse files

ceph: get snap_rwsem read lock in handle_cap_export for ceph_add_cap 



ceph_add_cap says in its function documentation that the caller should
hold the read lock on the session snap_rwsem. Furthermore, not only
ceph_add_cap needs that lock, when it calls to ceph_lookup_snap_realm it
eventually calls ceph_get_snap_realm which states via lockdep that
snap_rwsem needs to be held. handle_cap_export calls ceph_add_cap
without that mdsc->snap_rwsem held. Thus, since ceph_get_snap_realm
and ceph_add_cap both need the lock, the common place to acquire that
lock is inside handle_cap_export.

Signed-off-by: default avatarNiels Dossche <dossche.niels@gmail.com>
Reviewed-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent dc9b0dc4

fs/ceph/caps.c

+3 −0
Original line number Diff line number Diff line
@@ -3870,6 +3870,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, 
	dout("handle_cap_export inode %p ci %p mds%d mseq %d target %d\n",

	     inode, ci, mds, mseq, target);

retry:

	down_read(&mdsc->snap_rwsem);

	spin_lock(&ci->i_ceph_lock);

	cap = __get_cap_for_mds(ci, mds);

	if (!cap || cap->cap_id != le64_to_cpu(ex->cap_id))
@@ -3933,6 +3934,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, 
	}



	spin_unlock(&ci->i_ceph_lock);

	up_read(&mdsc->snap_rwsem);

	mutex_unlock(&session->s_mutex);



	/* open target session */
@@ -3958,6 +3960,7 @@ static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex, 


out_unlock:

	spin_unlock(&ci->i_ceph_lock);

	up_read(&mdsc->snap_rwsem);

	mutex_unlock(&session->s_mutex);

	if (tsession) {

		mutex_unlock(&tsession->s_mutex);