From d79698da32b317e96216236f265a9b72b78ae568 Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Tue, 26 Jul 2011 11:31:26 -0700 Subject: ceph: document unlocked d_parent accesses For the most part we don't care about racing with rename when directing MDS requests; either the old or new parent is fine. Document that, and do some minor cleanup. Reviewed-by: Yehuda Sadeh Signed-off-by: Sage Weil --- fs/ceph/mds_client.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'fs/ceph/mds_client.c') diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 66a8939cc518..fee028b5332e 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -621,6 +621,12 @@ static void __unregister_request(struct ceph_mds_client *mdsc, */ struct dentry *get_nonsnap_parent(struct dentry *dentry) { + /* + * we don't need to worry about protecting the d_parent access + * here because we never renaming inside the snapped namespace + * except to resplice to another snapdir, and either the old or new + * result is a valid result. + */ while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP) dentry = dentry->d_parent; return dentry; @@ -656,7 +662,9 @@ static int __choose_mds(struct ceph_mds_client *mdsc, if (req->r_inode) { inode = req->r_inode; } else if (req->r_dentry) { - struct inode *dir = req->r_dentry->d_parent->d_inode; + /* ignore race with rename; old or new d_parent is okay */ + struct dentry *parent = req->r_dentry->d_parent; + struct inode *dir = parent->d_inode; if (dir->i_sb != mdsc->fsc->sb) { /* not this fs! */ @@ -664,8 +672,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc, } else if (ceph_snap(dir) != CEPH_NOSNAP) { /* direct snapped/virtual snapdir requests * based on parent dir inode */ - struct dentry *dn = - get_nonsnap_parent(req->r_dentry->d_parent); + struct dentry *dn = get_nonsnap_parent(parent); inode = dn->d_inode; dout("__choose_mds using nonsnap parent %p\n", inode); } else if (req->r_dentry->d_inode) { -- cgit v1.2.3