gfs2: When freezing gfs2, use GL_EXACT and not GL_NOCACHE

Before this patch, the freeze code in gfs2 specified GL_NOCACHE in
several places. That's wrong because we always want to know the state
of whether the file system is frozen.

There was also a problem with freeze/thaw transitioning the glock from
frozen (EX) to thawed (SH) because gfs2 will normally grant glocks in EX
to processes that request it in SH mode, unless GL_EXACT is specified.
Therefore, the freeze/thaw code, which tried to reacquire the glock in
SH mode would get the glock in EX mode, and miss the transition from EX
to SH. That made it think the thaw had completed normally, but since the
glock was still cached in EX, other nodes could not freeze again.

This patch removes the GL_NOCACHE flag to allow the freeze glock to be
cached. It also adds the GL_EXACT flag so the glock is fully transitioned
from EX to SH, thereby allowing future freeze operations.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/recovery.c

@@ -364,8 +364,8 @@ void gfs2_recover_func(struct work_struct *work)
 		/* Acquire a shared hold on the freeze lock */
 
 		error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED,
-					   LM_FLAG_NOEXP | LM_FLAG_PRIORITY,
-					   &thaw_gh);
+					   LM_FLAG_NOEXP | LM_FLAG_PRIORITY |
+					   GL_EXACT, &thaw_gh);
 		if (error)
 			goto fail_gunlock_ji;
 

fs/gfs2/super.c

@@ -167,7 +167,7 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
 	if (error)
 		return error;
 
-	error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED, 0,
+	error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED, GL_EXACT,
 				   &freeze_gh);
 	if (error)
 		goto fail_threads;
@@ -203,7 +203,6 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
 	return 0;
 
 fail:
-	freeze_gh.gh_flags |= GL_NOCACHE;
 	gfs2_glock_dq_uninit(&freeze_gh);
 fail_threads:
 	if (sdp->sd_quotad_process)
@@ -430,7 +429,7 @@ static int gfs2_lock_fs_check_clean(struct gfs2_sbd *sdp)
 	}
 
 	error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_EXCLUSIVE,
-				   GL_NOCACHE, &sdp->sd_freeze_gh);
+				   0, &sdp->sd_freeze_gh);
 	if (error)
 		goto out;
 
@@ -613,13 +612,14 @@ int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
 	    !gfs2_glock_is_locked_by_me(sdp->sd_freeze_gl)) {
 		if (!log_write_allowed) {
 			error = gfs2_glock_nq_init(sdp->sd_freeze_gl,
-						   LM_ST_SHARED, GL_NOCACHE |
-						   LM_FLAG_TRY, &freeze_gh);
+						   LM_ST_SHARED,
+						   LM_FLAG_TRY | GL_EXACT,
+						   &freeze_gh);
 			if (error == GLR_TRYFAILED)
 				error = 0;
 		} else {
 			error = gfs2_glock_nq_init(sdp->sd_freeze_gl,
-						   LM_ST_SHARED, GL_NOCACHE,
+						   LM_ST_SHARED, GL_EXACT,
 						   &freeze_gh);
 			if (error && !gfs2_withdrawn(sdp))
 				return error;
@@ -761,7 +761,7 @@ void gfs2_freeze_func(struct work_struct *work)
 	struct super_block *sb = sdp->sd_vfs;
 
 	atomic_inc(&sb->s_active);
-	error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED, 0,
+	error = gfs2_glock_nq_init(sdp->sd_freeze_gl, LM_ST_SHARED, GL_EXACT,
 				   &freeze_gh);
 	if (error) {
 		fs_info(sdp, "GFS2: couldn't get freeze lock : %d\n", error);
@@ -774,8 +774,6 @@ void gfs2_freeze_func(struct work_struct *work)
 				error);
 			gfs2_assert_withdraw(sdp, 0);
 		}
-		if (!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
-			freeze_gh.gh_flags |= GL_NOCACHE;
 		gfs2_glock_dq_uninit(&freeze_gh);
 	}
 	deactivate_super(sb);