ceph: handle the case where a dentry has been renamed on outstanding req

It's possible for us to issue a lookup to revalidate a dentry
concurrently with a rename. If done in the right order, then we could
end up processing dentry info in the reply that no longer reflects the
state of the dentry.

If req->r_dentry->d_name differs from the one in the trace, then just
ignore the trace in the reply. We only need to do this however if the
parent's i_rwsem is not held.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 2d61ddd..c2feb31 100644 (file)
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1163,6 +1163,19 @@ static int splice_dentry(struct dentry **pdn, struct inode *in)
        return 0;
 }
 
+static int d_name_cmp(struct dentry *dentry, const char *name, size_t len)
+{
+       int ret;
+
+       /* take d_lock to ensure dentry->d_name stability */
+       spin_lock(&dentry->d_lock);
+       ret = dentry->d_name.len - len;
+       if (!ret)
+               ret = memcmp(dentry->d_name.name, name, len);
+       spin_unlock(&dentry->d_lock);
+       return ret;
+}
+
 /*
  * Incorporate results into the local cache.  This is either just
  * one inode, or a directory, dentry, and possibly linked-to inode (e.g.,
@@ -1412,7 +1425,8 @@ retry_lookup:
                err = splice_dentry(&req->r_dentry, in);
                if (err < 0)
                        goto done;
-       } else if (rinfo->head->is_dentry) {
+       } else if (rinfo->head->is_dentry &&
+                  !d_name_cmp(req->r_dentry, rinfo->dname, rinfo->dname_len)) {
                struct ceph_vino *ptvino = NULL;
 
                if ((le32_to_cpu(rinfo->diri.in->cap.caps) & CEPH_CAP_FILE_SHARED) ||