Commit 8cfc0c7e authored by Jeff Layton's avatar Jeff Layton Committed by Ilya Dryomov
Browse files

ceph: properly handle statfs on multifs setups 

ceph_statfs currently stuffs the cluster fsid into the f_fsid field.
This was fine when we only had a single filesystem per cluster, but now
that we have multiples we need to use something that will vary between
them.

Change ceph_statfs to xor each 32-bit chunk of the fsid (aka cluster id)
into the lower bits of the statfs->f_fsid. Change the lower bits to hold
the fscid (filesystem ID within the cluster).

That should give us a value that is guaranteed to be unique between
filesystems within a cluster, and should minimize the chance of
collisions between mounts of different clusters.

URL: https://tracker.ceph.com/issues/52812


Reported-by: default avatarSachin Prabhu <sprabhu@redhat.com>
Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarXiubo Li <xiubli@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 631ed4b0

fs/ceph/super.c

+6 −5
Original line number Diff line number Diff line
@@ -52,8 +52,7 @@ static int ceph_statfs(struct dentry *dentry, struct kstatfs *buf) 
	struct ceph_fs_client *fsc = ceph_inode_to_client(d_inode(dentry));

	struct ceph_mon_client *monc = &fsc->client->monc;

	struct ceph_statfs st;

	u64 fsid;

	int err;

	int i, err;

	u64 data_pool;



	if (fsc->mdsc->mdsmap->m_num_data_pg_pools == 1) {
@@ -99,12 +98,14 @@ static int ceph_statfs(struct dentry *dentry, struct kstatfs *buf) 
	buf->f_namelen = NAME_MAX;



	/* Must convert the fsid, for consistent values across arches */

	buf->f_fsid.val[0] = 0;

	mutex_lock(&monc->mutex);

	fsid = le64_to_cpu(*(__le64 *)(&monc->monmap->fsid)) ^

	       le64_to_cpu(*((__le64 *)&monc->monmap->fsid + 1));

	for (i = 0 ; i < sizeof(monc->monmap->fsid) / sizeof(__le32) ; ++i)

		buf->f_fsid.val[0] ^= le32_to_cpu(((__le32 *)&monc->monmap->fsid)[i]);

	mutex_unlock(&monc->mutex);



	buf->f_fsid = u64_to_fsid(fsid);

	/* fold the fs_cluster_id into the upper bits */

	buf->f_fsid.val[1] = monc->fs_cluster_id;



	return 0;

}