ceph: simplify caps revocation, fix for multimds

The caps revocation should either initiate writeback, invalidateion, or
call check_caps to ack or do the dirty work.  The primary question is
whether we can get away with only checking the auth cap or whether all
caps need to be checked.

The old code was doing...something else.  At the very least, revocations
from non-auth MDSs could break by triggering the "check auth cap only"
case.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/caps.c

@@ -2278,8 +2278,8 @@ static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 	 * try to invalidate (once).  (If there are dirty buffers, we
 	 * will invalidate _after_ writeback.)
 	 */
-	if (((cap->issued & ~newcaps) & (CEPH_CAP_FILE_CACHE|
-					 CEPH_CAP_FILE_LAZYIO)) &&
+	if (((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
+	    (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
 	    !ci->i_wrbuffer_ref) {
 		if (try_nonblocking_invalidate(inode) == 0) {
 			revoked_rdcache = 1;
@@ -2371,16 +2371,22 @@ static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 
 	/* revocation, grant, or no-op? */
 	if (cap->issued & ~newcaps) {
-		dout("revocation: %s -> %s\n", ceph_cap_string(cap->issued),
-		     ceph_cap_string(newcaps));
-		if ((used & ~newcaps) & CEPH_CAP_FILE_BUFFER)
-			writeback = 1; /* will delay ack */
-		else if (dirty & ~newcaps)
-			check_caps = 1;  /* initiate writeback in check_caps */
-		else if (((used & ~newcaps) & (CEPH_CAP_FILE_CACHE|
-					       CEPH_CAP_FILE_LAZYIO)) == 0 ||
-			   revoked_rdcache)
-			check_caps = 2;     /* send revoke ack in check_caps */
+		int revoking = cap->issued & ~newcaps;
+
+		dout("revocation: %s -> %s (revoking %s)\n",
+		     ceph_cap_string(cap->issued),
+		     ceph_cap_string(newcaps),
+		     ceph_cap_string(revoking));
+		if (revoking & CEPH_CAP_FILE_BUFFER)
+			writeback = 1;  /* initiate writeback; will delay ack */
+		else if (revoking == CEPH_CAP_FILE_CACHE &&
+			 (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
+			 queue_invalidate)
+			; /* do nothing yet, invalidation will be queued */
+		else if (cap == ci->i_auth_cap)
+			check_caps = 1; /* check auth cap only */
+		else
+			check_caps = 2; /* check all caps */
 		cap->issued = newcaps;
 		cap->implemented |= newcaps;
 	} else if (cap->issued == newcaps) {