gfs2: Convert function bh_get to use iomap

Before this patch, function bh_get used block_map to figure out the
block it needed to read in from the quota_change file. This patch
changes it to use iomap directly to make it more efficient.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/quota.c

@@ -365,11 +365,12 @@ static void slot_put(struct gfs2_quota_data *qd)
 static int bh_get(struct gfs2_quota_data *qd)
 {
 	struct gfs2_sbd *sdp = qd->qd_gl->gl_name.ln_sbd;
-	struct gfs2_inode *ip = GFS2_I(sdp->sd_qc_inode);
+	struct inode *inode = sdp->sd_qc_inode;
+	struct gfs2_inode *ip = GFS2_I(inode);
 	unsigned int block, offset;
 	struct buffer_head *bh;
+	struct iomap iomap = { };
 	int error;
-	struct buffer_head bh_map = { .b_state = 0, .b_blocknr = 0 };
 
 	mutex_lock(&sdp->sd_quota_mutex);
 
@@ -381,11 +382,17 @@ static int bh_get(struct gfs2_quota_data *qd)
 	block = qd->qd_slot / sdp->sd_qc_per_block;
 	offset = qd->qd_slot % sdp->sd_qc_per_block;
 
-	bh_map.b_size = BIT(ip->i_inode.i_blkbits);
-	error = gfs2_block_map(&ip->i_inode, block, &bh_map, 0);
+	error = gfs2_iomap_get(inode,
+			       (loff_t)block << inode->i_blkbits,
+			       i_blocksize(inode), &iomap);
 	if (error)
 		goto fail;
-	error = gfs2_meta_read(ip->i_gl, bh_map.b_blocknr, DIO_WAIT, 0, &bh);
+	error = -ENOENT;
+	if (iomap.type != IOMAP_MAPPED)
+		goto fail;
+
+	error = gfs2_meta_read(ip->i_gl, iomap.addr >> inode->i_blkbits,
+			       DIO_WAIT, 0, &bh);
 	if (error)
 		goto fail;
 	error = -EIO;