gfs2: sanitize the gdlm_ast -> finish_xmote interface

When gdlm_ast() is called with a non-zero status code, this means that
the requested operation did not succeed and the current lock state
didn't change.  Turn that into a non-zero LM_OUT_* status code (with ret
& ~LM_OUT_ST_MASK != 0) instead of pretending that dlm returned the
current lock state.

That way, we can easily change finish_xmote() to only update
gl->gl_state when the state has actually changed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>

3 files changed, 34 insertions, 14 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index ea96113edbe3..a3a5edc28a51 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -590,20 +590,25 @@ static void gfs2_demote_wake(struct gfs2_glock *gl)
 static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
 {
 	const struct gfs2_glock_operations *glops = gl->gl_ops;
-	struct gfs2_holder *gh;
-	unsigned state = ret & LM_OUT_ST_MASK;
 
-	trace_gfs2_glock_state_change(gl, state);
-	state_change(gl, state);
-	gh = find_first_waiter(gl);
+	if (!(ret & ~LM_OUT_ST_MASK)) {
+		unsigned state = ret & LM_OUT_ST_MASK;
+
+		trace_gfs2_glock_state_change(gl, state);
+		state_change(gl, state);
+	}
+
 
 	/* Demote to UN request arrived during demote to SH or DF */
 	if (test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) &&
-	    state != LM_ST_UNLOCKED && gl->gl_demote_state == LM_ST_UNLOCKED)
+	    gl->gl_state != LM_ST_UNLOCKED &&
+	    gl->gl_demote_state == LM_ST_UNLOCKED)
 		gl->gl_target = LM_ST_UNLOCKED;
 
 	/* Check for state != intended state */
-	if (unlikely(state != gl->gl_target)) {
+	if (unlikely(gl->gl_state != gl->gl_target)) {
+		struct gfs2_holder *gh = find_first_waiter(gl);
+
 		if (gh && (ret & LM_OUT_CANCELED))
 			gfs2_holder_wake(gh);
 		if (gh && !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags)) {
@@ -629,7 +634,7 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
 				goto out;
 			}
 		}
-		switch(state) {
+		switch(gl->gl_state) {
 		/* Unlocked due to conversion deadlock, try again */
 		case LM_ST_UNLOCKED:
 			do_xmote(gl, gh, gl->gl_target);
@@ -640,8 +645,10 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
 			do_xmote(gl, gh, LM_ST_UNLOCKED);
 			break;
 		default: /* Everything else */
-			fs_err(gl->gl_name.ln_sbd, "wanted %u got %u\n",
-			       gl->gl_target, state);
+			fs_err(gl->gl_name.ln_sbd,
+			       "glock %u:%llu requested=%u ret=%u\n",
+			       gl->gl_name.ln_type, gl->gl_name.ln_number,
+			       gl->gl_req, ret);
 			GLOCK_BUG_ON(gl, 1);
 		}
 		return;
@@ -650,7 +657,7 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
 	/* Fast path - we got what we asked for */
 	if (test_and_clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags))
 		gfs2_demote_wake(gl);
-	if (state != LM_ST_UNLOCKED) {
+	if (gl->gl_state != LM_ST_UNLOCKED) {
 		if (glops->go_xmote_bh) {
 			int rv;
 
diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index c171f745650f..9339a3bff6ee 100644
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -92,12 +92,22 @@ enum {
  * LM_OUT_ST_MASK
  * Masks the lower two bits of lock state in the returned value.
  *
+ * LM_OUT_TRY_AGAIN
+ * The trylock request failed.
+ *
+ * LM_OUT_DEADLOCK
+ * The lock request failed because it would deadlock.
+ *
  * LM_OUT_CANCELED
  * The lock request was canceled.
  *
+ * LM_OUT_ERROR
+ * The lock request timed out or failed.
  */
 
 #define LM_OUT_ST_MASK		0x00000003
+#define LM_OUT_TRY_AGAIN	0x00000020
+#define LM_OUT_DEADLOCK		0x00000010
 #define LM_OUT_CANCELED		0x00000008
 #define LM_OUT_ERROR		0x00000004
 
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index 7cb9d216d8bb..cee5d199d2d8 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -119,7 +119,7 @@ static inline void gfs2_update_request_times(struct gfs2_glock *gl)
 static void gdlm_ast(void *arg)
 {
 	struct gfs2_glock *gl = arg;
-	unsigned ret = gl->gl_state;
+	unsigned ret;
 
 	/* If the glock is dead, we only react to a dlm_unlock() reply. */
 	if (__lockref_is_dead(&gl->gl_lockref) &&
@@ -139,13 +139,16 @@ static void gdlm_ast(void *arg)
 		gfs2_glock_free(gl);
 		return;
 	case -DLM_ECANCEL: /* Cancel while getting lock */
-		ret |= LM_OUT_CANCELED;
+		ret = LM_OUT_CANCELED;
 		goto out;
 	case -EAGAIN: /* Try lock fails */
+		ret = LM_OUT_TRY_AGAIN;
+		goto out;
 	case -EDEADLK: /* Deadlock detected */
+		ret = LM_OUT_DEADLOCK;
 		goto out;
 	case -ETIMEDOUT: /* Canceled due to timeout */
-		ret |= LM_OUT_ERROR;
+		ret = LM_OUT_ERROR;
 		goto out;
 	case 0: /* Success */
 		break;