gfs2: Don't release and reacquire local statfs bh

Before this patch, several functions in gfs2 related to the updating
of the statfs file used a newly acquired/read buffer_head for the
local statfs file. This is completely unnecessary, because other nodes
should never update it. Recreating the buffer is a waste of time.

This patch allows gfs2 to read in the local statefs buffer_head at
mount time and keep it around until unmount time.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

fs/gfs2/aops.c

@@ -574,10 +574,9 @@ void adjust_fs_space(struct inode *inode)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
-	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
 	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
 	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
-	struct buffer_head *m_bh, *l_bh;
+	struct buffer_head *m_bh;
 	u64 fs_total, new_free;
 
 	if (gfs2_trans_begin(sdp, 2 * RES_STATFS, 0) != 0)
@@ -600,11 +599,7 @@ void adjust_fs_space(struct inode *inode)
 		(unsigned long long)new_free);
 	gfs2_statfs_change(sdp, new_free, new_free, 0);
 
-	if (gfs2_meta_inode_buffer(l_ip, &l_bh) != 0)
-		goto out2;
-	update_statfs(sdp, m_bh, l_bh);
-	brelse(l_bh);
-out2:
+	update_statfs(sdp, m_bh);
 	brelse(m_bh);
 out:
 	sdp->sd_rindex_uptodate = 0;

fs/gfs2/incore.h

@@ -768,6 +768,7 @@ struct gfs2_sbd {
 	struct gfs2_glock *sd_jinode_gl;
 
 	struct gfs2_holder sd_sc_gh;
+	struct buffer_head *sd_sc_bh;
 	struct gfs2_holder sd_qc_gh;
 
 	struct completion sd_journal_ready;

fs/gfs2/ops_fstype.c

@@ -696,8 +696,16 @@ static int init_statfs(struct gfs2_sbd *sdp)
 		fs_err(sdp, "can't lock local \"sc\" file: %d\n", error);
 		goto free_local;
 	}
+	/* read in the local statfs buffer - other nodes don't change it. */
+	error = gfs2_meta_inode_buffer(ip, &sdp->sd_sc_bh);
+	if (error) {
+		fs_err(sdp, "Cannot read in local statfs: %d\n", error);
+		goto unlock_sd_gh;
+	}
 	return 0;
 
+unlock_sd_gh:
+	gfs2_glock_dq_uninit(&sdp->sd_sc_gh);
 free_local:
 	free_local_statfs_inodes(sdp);
 	iput(pn);
@@ -711,6 +719,7 @@ static int init_statfs(struct gfs2_sbd *sdp)
 static void uninit_statfs(struct gfs2_sbd *sdp)
 {
 	if (!sdp->sd_args.ar_spectator) {
+		brelse(sdp->sd_sc_bh);
 		gfs2_glock_dq_uninit(&sdp->sd_sc_gh);
 		free_local_statfs_inodes(sdp);
 	}

fs/gfs2/super.c

@@ -178,9 +178,8 @@ int gfs2_statfs_init(struct gfs2_sbd *sdp)
 {
 	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
 	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
-	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
 	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
-	struct buffer_head *m_bh, *l_bh;
+	struct buffer_head *m_bh;
 	struct gfs2_holder gh;
 	int error;
 
@@ -199,21 +198,15 @@ int gfs2_statfs_init(struct gfs2_sbd *sdp)
 				      sizeof(struct gfs2_dinode));
 		spin_unlock(&sdp->sd_statfs_spin);
 	} else {
-		error = gfs2_meta_inode_buffer(l_ip, &l_bh);
-		if (error)
-			goto out_m_bh;
-
 		spin_lock(&sdp->sd_statfs_spin);
 		gfs2_statfs_change_in(m_sc, m_bh->b_data +
 				      sizeof(struct gfs2_dinode));
-		gfs2_statfs_change_in(l_sc, l_bh->b_data +
+		gfs2_statfs_change_in(l_sc, sdp->sd_sc_bh->b_data +
 				      sizeof(struct gfs2_dinode));
 		spin_unlock(&sdp->sd_statfs_spin);
 
-		brelse(l_bh);
 	}
 
-out_m_bh:
 	brelse(m_bh);
 out:
 	gfs2_glock_dq_uninit(&gh);
@@ -226,22 +219,17 @@ void gfs2_statfs_change(struct gfs2_sbd *sdp, s64 total, s64 free,
 	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
 	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
 	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
-	struct buffer_head *l_bh;
 	s64 x, y;
 	int need_sync = 0;
-	int error;
-
-	error = gfs2_meta_inode_buffer(l_ip, &l_bh);
-	if (error)
-		return;
 
-	gfs2_trans_add_meta(l_ip->i_gl, l_bh);
+	gfs2_trans_add_meta(l_ip->i_gl, sdp->sd_sc_bh);
 
 	spin_lock(&sdp->sd_statfs_spin);
 	l_sc->sc_total += total;
 	l_sc->sc_free += free;
 	l_sc->sc_dinodes += dinodes;
-	gfs2_statfs_change_out(l_sc, l_bh->b_data + sizeof(struct gfs2_dinode));
+	gfs2_statfs_change_out(l_sc, sdp->sd_sc_bh->b_data +
+			       sizeof(struct gfs2_dinode));
 	if (sdp->sd_args.ar_statfs_percent) {
 		x = 100 * l_sc->sc_free;
 		y = m_sc->sc_free * sdp->sd_args.ar_statfs_percent;
@@ -250,20 +238,18 @@ void gfs2_statfs_change(struct gfs2_sbd *sdp, s64 total, s64 free,
 	}
 	spin_unlock(&sdp->sd_statfs_spin);
 
-	brelse(l_bh);
 	if (need_sync)
 		gfs2_wake_up_statfs(sdp);
 }
 
-void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
-		   struct buffer_head *l_bh)
+void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh)
 {
 	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
 	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
 	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
 	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
 
-	gfs2_trans_add_meta(l_ip->i_gl, l_bh);
+	gfs2_trans_add_meta(l_ip->i_gl, sdp->sd_sc_bh);
 	gfs2_trans_add_meta(m_ip->i_gl, m_bh);
 
 	spin_lock(&sdp->sd_statfs_spin);
@@ -271,7 +257,7 @@ void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
 	m_sc->sc_free += l_sc->sc_free;
 	m_sc->sc_dinodes += l_sc->sc_dinodes;
 	memset(l_sc, 0, sizeof(struct gfs2_statfs_change));
-	memset(l_bh->b_data + sizeof(struct gfs2_dinode),
+	memset(sdp->sd_sc_bh->b_data + sizeof(struct gfs2_dinode),
 	       0, sizeof(struct gfs2_statfs_change));
 	gfs2_statfs_change_out(m_sc, m_bh->b_data + sizeof(struct gfs2_dinode));
 	spin_unlock(&sdp->sd_statfs_spin);
@@ -281,11 +267,10 @@ int gfs2_statfs_sync(struct super_block *sb, int type)
 {
 	struct gfs2_sbd *sdp = sb->s_fs_info;
 	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
-	struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
 	struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
 	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
 	struct gfs2_holder gh;
-	struct buffer_head *m_bh, *l_bh;
+	struct buffer_head *m_bh;
 	int error;
 
 	error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE, GL_NOCACHE,
@@ -306,21 +291,15 @@ int gfs2_statfs_sync(struct super_block *sb, int type)
 	}
 	spin_unlock(&sdp->sd_statfs_spin);
 
-	error = gfs2_meta_inode_buffer(l_ip, &l_bh);
-	if (error)
-		goto out_bh;
-
 	error = gfs2_trans_begin(sdp, 2 * RES_DINODE, 0);
 	if (error)
-		goto out_bh2;
+		goto out_bh;
 
-	update_statfs(sdp, m_bh, l_bh);
+	update_statfs(sdp, m_bh);
 	sdp->sd_statfs_force_sync = 0;
 
 	gfs2_trans_end(sdp);
 
-out_bh2:
-	brelse(l_bh);
 out_bh:
 	brelse(m_bh);
 out_unlock:
@@ -626,6 +605,7 @@ static void gfs2_put_super(struct super_block *sb)
 			gfs2_glock_dq_uninit(&sdp->sd_journal_gh);
 		if (gfs2_holder_initialized(&sdp->sd_jinode_gh))
 			gfs2_glock_dq_uninit(&sdp->sd_jinode_gh);
+		brelse(sdp->sd_sc_bh);
 		gfs2_glock_dq_uninit(&sdp->sd_sc_gh);
 		gfs2_glock_dq_uninit(&sdp->sd_qc_gh);
 		free_local_statfs_inodes(sdp);

fs/gfs2/super.h

@@ -43,8 +43,7 @@ extern void gfs2_statfs_change_in(struct gfs2_statfs_change_host *sc,
 				  const void *buf);
 extern void gfs2_statfs_change_out(const struct gfs2_statfs_change_host *sc,
 				   void *buf);
-extern void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
-			  struct buffer_head *l_bh);
+extern void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh);
 extern int gfs2_statfs_sync(struct super_block *sb, int type);
 extern void gfs2_freeze_func(struct work_struct *work);