ceph: fix flushing of caps vs cap import

If we are mid-flush and a cap is migrated to another node, we need to
resend the cap flush message to the new MDS, and do so with the original
flush_seq to avoid leaking across a sync boundary. Previously we didn't
redo the flush (we only flushed newly dirty data), which would cause a
later sync to hang forever.

Signed-off-by: Sage Weil <[e-mail]>

fs/ceph/caps.c

···
 		/* NOTE: no side-effects allowed, until we take s_mutex */
 
 		revoking = cap->implemented & ~cap->issued;
-		if (revoking)
-			dout(" mds%d revoking %s\n", cap->mds,
-			     ceph_cap_string(revoking));
+		dout(" mds%d cap %p issued %s implemented %s revoking %s\n",
+		     cap->mds, cap, ceph_cap_string(cap->issued),
+		     ceph_cap_string(cap->implemented),
+		     ceph_cap_string(revoking));
 
 		if (cap == ci->i_auth_cap &&
 		    (cap->issued & CEPH_CAP_FILE_WR)) {
···
 			       cap, session->s_mds);
 			spin_unlock(&inode->i_lock);
 		}
+	}
+}
+
+static void kick_flushing_inode_caps(struct ceph_mds_client *mdsc,
+				     struct ceph_mds_session *session,
+				     struct inode *inode)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_cap *cap;
+	int delayed = 0;
+
+	spin_lock(&inode->i_lock);
+	cap = ci->i_auth_cap;
+	dout("kick_flushing_inode_caps %p flushing %s flush_seq %lld\n", inode,
+	     ceph_cap_string(ci->i_flushing_caps), ci->i_cap_flush_seq);
+	__ceph_flush_snaps(ci, &session, 1);
+	if (ci->i_flushing_caps) {
+		delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH,
+				     __ceph_caps_used(ci),
+				     __ceph_caps_wanted(ci),
+				     cap->issued | cap->implemented,
+				     ci->i_flushing_caps, NULL);
+		if (delayed) {
+			spin_lock(&inode->i_lock);
+			__cap_delay_requeue(mdsc, ci);
+			spin_unlock(&inode->i_lock);
+		}
+	} else {
+		spin_unlock(&inode->i_lock);
 	}
 }
 
···
 	ceph_add_cap(inode, session, cap_id, -1,
 		     issued, wanted, seq, mseq, realmino, CEPH_CAP_FLAG_AUTH,
 		     NULL /* no caps context */);
-	try_flush_caps(inode, session, NULL);
+	kick_flushing_inode_caps(mdsc, session, inode);
 	up_read(&mdsc->snap_rwsem);
 
 	/* make sure we re-request max_size, if necessary */