ceph: fix truncation when not holding caps

A truncation should occur when either we have the
specified caps for the file, or (in cases where we are
not the only ones referencing the file) when it is mapped
or when it is opened. The latter two cases were not
handled.
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/inode.c

@@ -416,9 +416,17 @@ int ceph_fill_file_size(struct inode *inode, int issued,
 			dout("truncate_seq %u -> %u\n",
 			     ci->i_truncate_seq, truncate_seq);
 			ci->i_truncate_seq = truncate_seq;
-			if (issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_RD|
+			/*
+			 * If we hold relevant caps, or in the case where we're
+			 * not the only client referencing this file and we
+			 * don't hold those caps, then we need to check whether
+			 * the file is either opened or mmaped
+			 */
+			if ((issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_RD|
 				      CEPH_CAP_FILE_WR|CEPH_CAP_FILE_BUFFER|
-				      CEPH_CAP_FILE_EXCL)) {
+				      CEPH_CAP_FILE_EXCL)) ||
+			    mapping_mapped(inode->i_mapping) ||
+			    __ceph_caps_file_wanted(ci)) {
 				ci->i_truncate_pending++;
 				queue_trunc = 1;
 			}