s390/tty3270: convert lines during output

The length of the screen line is variable with the 3270 protocol.
For each attribute (foreground, background color, highlighting etc)
we need 3 bytes: the set attribute order, the attribute number, and
the value of the attribute. This means that depending on screen content,
we might end up 3*3 bytes addtional data for a single character.

Allocating the maximum possible amount of memory is quite a lot, and
we cannot easily extend the lines by allocating memory because we
might get called from atomic context. Failing to extend the memory
would also be bad as that would mean that we could miss kernel messages
in oom conditions. Therefore move the conversion to a 3270 datastream
to tty3270_update(), and use only single line buffer.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

2 files changed, 102 insertions, 238 deletions

diff --git a/drivers/s390/char/con3270.c b/drivers/s390/char/con3270.c
index e91a96a958e5..00e6e01cf8c8 100644
--- a/drivers/s390/char/con3270.c
+++ b/drivers/s390/char/con3270.c
@@ -33,7 +33,7 @@
 #include "keyboard.h"
 
 #define TTY3270_CHAR_BUF_SIZE 256
-#define TTY3270_OUTPUT_BUFFER_SIZE 1024
+#define TTY3270_OUTPUT_BUFFER_SIZE 4096
 #define TTY3270_STRING_PAGES 5
 
 #define TTY3270_SCREEN_PAGES 8 /* has to be power-of-two */
@@ -82,7 +82,6 @@ struct tty3270 {
 
 	/* Output stuff. */
 	struct list_head lines;		/* List of lines. */
-	struct list_head update;	/* List of lines to update. */
 	unsigned char wcc;		/* Write control character. */
 	int nr_lines;			/* # lines in list. */
 	int nr_up;			/* # lines up in history. */
@@ -90,6 +89,8 @@ struct tty3270 {
 	struct raw3270_request *write;	/* Single write request. */
 	struct timer_list timer;	/* Output delay timer. */
 	char *converted_line;		/* RAW 3270 data stream */
+	unsigned int line_view_start;	/* Start of visible area */
+	unsigned int line_write_start;	/* current write position */
 
 	/* Current tty screen. */
 	unsigned int cx, cy;		/* Current output position. */
@@ -127,14 +128,12 @@ struct tty3270 {
 
 /* tty3270->update_flags. See tty3270_update for details. */
 #define TTY_UPDATE_ERASE	1	/* Use EWRITEA instead of WRITE. */
-#define TTY_UPDATE_LIST		2	/* Update lines in tty3270->update. */
 #define TTY_UPDATE_INPUT	4	/* Update input line. */
 #define TTY_UPDATE_STATUS	8	/* Update status line. */
 #define TTY_UPDATE_ALL		16	/* Recreate screen. */
 
 #define TTY3270_INPUT_AREA_ROWS 2
 
-static void tty3270_update(struct timer_list *);
 /*
  * Setup timeout for a device. On timeout trigger an update.
  */
@@ -184,6 +183,21 @@ static char *tty3270_add_sf(struct tty3270 *tp, char *cp, char type)
 	return cp;
 }
 
+static int tty3270_line_increment(struct tty3270 *tp, unsigned int line, unsigned int incr)
+{
+	return (line + incr) & (tp->allocated_lines - 1);
+}
+
+static struct tty3270_line *tty3270_get_write_line(struct tty3270 *tp, unsigned int num)
+{
+	return tp->screen + tty3270_line_increment(tp, tp->line_write_start, num);
+}
+
+static struct tty3270_line *tty3270_get_view_line(struct tty3270 *tp, unsigned int num)
+{
+	return tp->screen + tty3270_line_increment(tp, tp->line_view_start, num - tp->nr_up);
+}
+
 /*
  * The input line are the two last lines of the screen.
  */
@@ -237,16 +251,6 @@ static void tty3270_create_prompt(struct tty3270 *tp)
  * The status line is the last line of the screen. It shows the string
  * "Running"/"Holding" in the lower right corner of the screen.
  */
-static void tty3270_update_status(struct tty3270 *tp)
-{
-	tp->update_flags |= TTY_UPDATE_STATUS;
-	tty3270_set_timer(tp, 1);
-}
-
-/*
- * The status line is the last line of the screen. It shows the string
- * "Running"/"Holding" in the lower right corner of the screen.
- */
 static int tty3270_add_status(struct tty3270 *tp)
 {
 	char *cp = tp->converted_line;
@@ -267,46 +271,16 @@ static int tty3270_add_status(struct tty3270 *tp)
  * Set output offsets to 3270 datastream fragment of a tty string.
  * (TO_SBA offset at the start and TO_RA offset at the end of the string)
  */
-static void tty3270_update_string(struct tty3270 *tp, struct string *line, int nr)
+static void tty3270_update_string(struct tty3270 *tp, char *line, int len, int nr)
 {
 	unsigned char *cp;
-
-	raw3270_buffer_address(tp->view.dev, line->string + 1, 0, nr);
-	cp = line->string + line->len - 4;
+	raw3270_buffer_address(tp->view.dev, line + 1, 0, nr);
+	cp = line + len - 4;
 	if (*cp == TO_RA)
 		raw3270_buffer_address(tp->view.dev, cp + 1, 0, nr + 1);
 }
 
 /*
- * Rebuild update list to print all lines.
- */
-static void tty3270_rebuild_update(struct tty3270 *tp)
-{
-	struct string *s, *n;
-	int line, nr_up;
-
-	/* 
-	 * Throw away update list and create a new one,
-	 * containing all lines that will fit on the screen.
-	 */
-	list_for_each_entry_safe(s, n, &tp->update, update)
-		list_del_init(&s->update);
-	line = tty3270_tty_rows(tp) - 1;
-	nr_up = tp->nr_up;
-	list_for_each_entry_reverse(s, &tp->lines, list) {
-		if (nr_up > 0) {
-			nr_up--;
-			continue;
-		}
-		tty3270_update_string(tp, s, line);
-		list_add(&s->update, &tp->update);
-		if (--line < 0)
-			break;
-	}
-	tp->update_flags |= TTY_UPDATE_LIST;
-}
-
-/*
  * Alloc string for size bytes. If there is not enough room in
  * freemem, free strings until there is room.
  */
@@ -318,63 +292,24 @@ static struct string *tty3270_alloc_string(struct tty3270 *tp, size_t size)
 	if (s)
 		return s;
 	list_for_each_entry_safe(s, n, &tp->lines, list) {
-		BUG_ON(tp->nr_lines <= tty3270_tty_rows(tp));
 		list_del(&s->list);
-		if (!list_empty(&s->update))
-			list_del(&s->update);
-		tp->nr_lines--;
 		if (free_string(&tp->freemem, s) >= size)
 			break;
 	}
-	s = alloc_string(&tp->freemem, size);
-	BUG_ON(!s);
-	if (tp->nr_up != 0 &&
-	    tp->nr_up + tty3270_tty_rows(tp) >= tp->nr_lines) {
-		tp->nr_up = tp->nr_lines - tp->view.rows + TTY3270_INPUT_AREA_ROWS;
-		tty3270_rebuild_update(tp);
-		tty3270_update_status(tp);
-	}
-	return s;
-}
-
-/*
- * Add an empty line to the list.
- */
-static void tty3270_blank_line(struct tty3270 *tp)
-{
-	static const unsigned char blueprint[] = {
-		TO_SBA, 0, 0, TO_SA, TAT_EXTHI, TAX_RESET,
-		TO_SA, TAT_FGCOLOR, TAC_RESET, TO_RA, 0, 0, 0,
-	};
-	struct string *s;
-
-	s = tty3270_alloc_string(tp, sizeof(blueprint));
-	memcpy(s->string, blueprint, sizeof(blueprint));
-	s->len = sizeof(blueprint);
-	list_add_tail(&s->list, &tp->lines);
-	tp->nr_lines++;
-	if (tp->nr_up != 0)
-		tp->nr_up++;
+	return alloc_string(&tp->freemem, size);
 }
 
-/*
- * Create a blank screen and remove all lines from the history.
- */
 static void tty3270_blank_screen(struct tty3270 *tp)
 {
-	struct string *s, *n;
+	struct tty3270_line *line;
 	int i;
 
-	for (i = 0; i < tty3270_tty_rows(tp); i++)
-		tp->screen[i].len = 0;
-	tp->nr_up = 0;
-	list_for_each_entry_safe(s, n, &tp->lines, list) {
-		list_del(&s->list);
-		if (!list_empty(&s->update))
-			list_del(&s->update);
-		tp->nr_lines--;
-		free_string(&tp->freemem, s);
+	for (i = 0; i < tty3270_tty_rows(tp); i++) {
+		line = tty3270_get_write_line(tp, i);
+		line->len = 0;
+		line->dirty = 1;
 	}
+	tp->nr_up = 0;
 }
 
 /*
@@ -393,14 +328,12 @@ static void tty3270_write_callback(struct raw3270_request *rq, void *data)
 	xchg(&tp->write, rq);
 }
 
-static int tty3270_required_length(struct tty3270 *tp, int line_nr)
+static int tty3270_required_length(struct tty3270 *tp, struct tty3270_line *line)
 {
 	unsigned char f_color, b_color, highlight;
-	struct tty3270_line *line;
 	struct tty3270_cell *cell;
 	int i, flen = 3;		/* Prefix (TO_SBA). */
 
-	line = tp->screen + line_nr;
 	flen += line->len;
 	highlight = TAX_RESET;
 	f_color = TAC_RESET;
@@ -515,55 +448,24 @@ static void tty3270_reset_attributes(struct tty3270_attribute *attr)
 	attr->b_color = TAC_RESET;
 }
 
-static struct string *tty3270_resize_line(struct tty3270 *tp, struct string *s, int newlen)
-{
-	struct string *n = tty3270_alloc_string(tp, newlen);
-
-	list_add(&n->list, &s->list);
-	list_del_init(&s->list);
-	if (!list_empty(&s->update))
-		list_del_init(&s->update);
-	free_string(&tp->freemem, s);
-	return n;
-}
-
 /*
  * Convert a tty3270_line to a 3270 data fragment usable for output.
  */
-static void tty3270_convert_line(struct tty3270 *tp, int line_nr)
+static unsigned int tty3270_convert_line(struct tty3270 *tp, struct tty3270_line *line)
 {
-	struct tty3270_line *line = tp->screen + line_nr;
 	struct tty3270_attribute attr;
-	struct string *s;
-	int flen, i;
+	int flen;
 	char *cp;
 
 	/* Determine how long the fragment will be. */
-	flen = tty3270_required_length(tp, line_nr);
-	/* Find the line in the list. */
-	i = tty3270_tty_rows(tp) - line_nr;
-	list_for_each_entry_reverse(s, &tp->lines, list)
-		if (--i <= 0)
-			break;
-	/*
-	 * Check if the line needs to get reallocated.
-	 */
-	if (s->len != flen)
-		s = tty3270_resize_line(tp, s, flen);
-
+	flen = tty3270_required_length(tp, line);
+	if (flen > PAGE_SIZE)
+		return 0;
 	/* Write 3270 data fragment. */
 	tty3270_reset_attributes(&attr);
-	cp = tty3270_add_attributes(tp, line, &attr, s->string);
+	cp = tty3270_add_attributes(tp, line, &attr, tp->converted_line);
 	cp = tty3270_add_reset_attributes(tp, line, cp, &attr);
-	if (tp->nr_up + line_nr < tty3270_tty_rows(tp)) {
-		/* Line is currently visible on screen. */
-		tty3270_update_string(tp, s, line_nr);
-		/* Add line to update list. */
-		if (list_empty(&s->update)) {
-			list_add_tail(&s->update, &tp->update);
-			tp->update_flags |= TTY_UPDATE_LIST;
-		}
-	}
+	return cp - (char *)tp->converted_line;
 }
 
 /*
@@ -572,12 +474,10 @@ static void tty3270_convert_line(struct tty3270 *tp, int line_nr)
 static void tty3270_update(struct timer_list *t)
 {
 	struct tty3270 *tp = from_timer(tp, t, timer);
-	static char invalid_sba[2] = { 0xff, 0xff };
 	struct raw3270_request *wrq;
+	struct tty3270_line *line;
 	unsigned long updated;
-	struct string *s, *n;
-	char *sba, *str;
-	int rc, len;
+	int i, rc, len;
 
 	wrq = xchg(&tp->write, 0);
 	if (!wrq) {
@@ -588,8 +488,7 @@ static void tty3270_update(struct timer_list *t)
 	spin_lock_irq(&tp->view.lock);
 	updated = 0;
 	if (tp->update_flags & TTY_UPDATE_ALL) {
-		tty3270_rebuild_update(tp);
-		tp->update_flags = TTY_UPDATE_ERASE | TTY_UPDATE_LIST |
+		tp->update_flags = TTY_UPDATE_ERASE |
 			TTY_UPDATE_INPUT | TTY_UPDATE_STATUS;
 	}
 	if (tp->update_flags & TTY_UPDATE_ERASE) {
@@ -619,33 +518,20 @@ static void tty3270_update(struct timer_list *t)
 					     tp->prompt->len) == 0)
 			updated |= TTY_UPDATE_INPUT;
 
-	sba = invalid_sba;
-	
-	if (tp->update_flags & TTY_UPDATE_LIST) {
-		/* Write strings in the update list to the screen. */
-		list_for_each_entry_safe(s, n, &tp->update, update) {
-			str = s->string;
-			len = s->len;
-			/*
-			 * Skip TO_SBA at the start of the string if the
-			 * last output position matches the start address
-			 * of this line.
-			 */
-			if (s->string[1] == sba[0] && s->string[2] == sba[1]) {
-				str += 3;
-				len -= 3;
-			}
-			if (raw3270_request_add_data(wrq, str, len) != 0)
-				break;
-			list_del_init(&s->update);
-			if (s->string[s->len - 4] == TO_RA)
-				sba = s->string + s->len - 3;
-			else
-				sba = invalid_sba;
-		}
-		if (list_empty(&tp->update))
-			updated |= TTY_UPDATE_LIST;
+	for (i = 0; i < tty3270_tty_rows(tp); i++) {
+		line = tty3270_get_view_line(tp, i);
+		if (!line->dirty)
+			continue;
+		len = tty3270_convert_line(tp, line);
+		tty3270_update_string(tp, tp->converted_line, len, i);
+		if (raw3270_request_add_data(wrq, tp->converted_line, len))
+			break;
+		line->dirty = 0;
 	}
+
+	if (i < tty3270_tty_rows(tp) - 1)
+		tty3270_set_timer(tp, 1);
+
 	wrq->callback = tty3270_write_callback;
 	rc = raw3270_start(&tp->view, wrq);
 	if (rc == 0) {
@@ -676,6 +562,8 @@ static void tty3270_rcl_add(struct tty3270 *tp, char *input, int len)
 		tp->rcl_nr--;
 	}
 	s = tty3270_alloc_string(tp, len);
+	if (!s)
+		return;
 	memcpy(s->string, input, len);
 	list_add_tail(&s->list, &tp->rcl_lines);
 	tp->rcl_nr++;
@@ -714,24 +602,29 @@ static void tty3270_exit_tty(struct kbd_data *kbd)
 	raw3270_deactivate_view(&tp->view);
 }
 
+static void tty3270_redraw(struct tty3270 *tp)
+{
+	int i;
+
+	for (i = 0; i < tty3270_tty_rows(tp); i++)
+		tty3270_get_view_line(tp, i)->dirty = 1;
+	tp->update_flags = TTY_UPDATE_ALL;
+	tty3270_set_timer(tp, 1);
+}
 /*
  * Scroll forward in history.
  */
 static void tty3270_scroll_forward(struct kbd_data *kbd)
 {
 	struct tty3270 *tp = container_of(kbd->port, struct tty3270, port);
-	int nr_up;
 
 	spin_lock_irq(&tp->view.lock);
-	nr_up = tp->nr_up - tp->view.rows + TTY3270_INPUT_AREA_ROWS;
-	if (nr_up < 0)
-		nr_up = 0;
-	if (nr_up != tp->nr_up) {
-		tp->nr_up = nr_up;
-		tty3270_rebuild_update(tp);
-		tp->update_flags |= TTY_UPDATE_STATUS;
-		tty3270_set_timer(tp, 1);
-	}
+
+	if (tp->nr_up >= tty3270_tty_rows(tp))
+		tp->nr_up -= tty3270_tty_rows(tp) / 2;
+	else
+		tp->nr_up = 0;
+	tty3270_redraw(tp);
 	spin_unlock_irq(&tp->view.lock);
 }
 
@@ -741,17 +634,12 @@ static void tty3270_scroll_forward(struct kbd_data *kbd)
 static void tty3270_scroll_backward(struct kbd_data *kbd)
 {
 	struct tty3270 *tp = container_of(kbd->port, struct tty3270, port);
-	int nr_up;
 
 	spin_lock_irq(&tp->view.lock);
-	nr_up = tp->nr_up + tty3270_tty_rows(tp);
-	if (nr_up + tty3270_tty_rows(tp) > tp->nr_lines)
-		nr_up = tp->nr_lines - tp->view.rows + TTY3270_INPUT_AREA_ROWS;
-	if (nr_up != tp->nr_up) {
-		tp->nr_up = nr_up;
-		tty3270_rebuild_update(tp);
-		tty3270_update_status(tp);
-	}
+	tp->nr_up += tty3270_tty_rows(tp) / 2;
+	if (tp->nr_up > tp->allocated_lines - tty3270_tty_rows(tp))
+		tp->nr_up = tp->allocated_lines - tty3270_tty_rows(tp);
+	tty3270_redraw(tp);
 	spin_unlock_irq(&tp->view.lock);
 }
 
@@ -781,11 +669,8 @@ static void tty3270_read_tasklet(unsigned long data)
 		len = tp->input->len - 6 - rrq->rescnt;
 		if (tp->inattr != TF_INPUTN)
 			tty3270_rcl_add(tp, input, len);
-		if (tp->nr_up > 0) {
+		if (tp->nr_up > 0)
 			tp->nr_up = 0;
-			tty3270_rebuild_update(tp);
-			tty3270_update_status(tp);
-		}
 		/* Clear input area. */
 		tty3270_update_prompt(tp, NULL, 0);
 		tty3270_set_timer(tp, 1);
@@ -931,7 +816,6 @@ static struct tty3270 *tty3270_alloc_view(void)
 		goto out_tp;
 	INIT_LIST_HEAD(&tp->freemem);
 	INIT_LIST_HEAD(&tp->lines);
-	INIT_LIST_HEAD(&tp->update);
 	INIT_LIST_HEAD(&tp->rcl_lines);
 	tp->rcl_max = 20;
 
@@ -1000,6 +884,7 @@ static void tty3270_free_view(struct tty3270 *tp)
 	for (pages = 0; pages < TTY3270_STRING_PAGES; pages++)
 		free_pages((unsigned long) tp->freemem_pages[pages], 0);
 	kfree(tp->freemem_pages);
+	free_page((unsigned long)tp->converted_line);
 	tty_port_destroy(&tp->port);
 	kfree(tp);
 }
@@ -1061,8 +946,7 @@ static void tty3270_resize(struct raw3270_view *view,
 	    old_cols == new_cols &&
 	    old_rows == new_rows) {
 		spin_lock_irq(&tp->view.lock);
-		tp->update_flags = TTY_UPDATE_ALL;
-		tty3270_set_timer(tp, 1);
+		tty3270_redraw(tp);
 		spin_unlock_irq(&tp->view.lock);
 		return;
 	}
@@ -1081,8 +965,6 @@ static void tty3270_resize(struct raw3270_view *view,
 
 	free_string(&tp->freemem, tp->prompt);
 	tty3270_create_prompt(tp);
-	while (tp->nr_lines < tty3270_tty_rows(tp))
-		tty3270_blank_line(tp);
 	tp->update_flags = TTY_UPDATE_ALL;
 	spin_unlock_irq(&tp->view.lock);
 	tty3270_free_screen(oscreen, old_allocated);
@@ -1154,7 +1036,7 @@ static int
 tty3270_create_view(int index, struct tty3270 **newtp)
 {
 	struct tty3270 *tp;
-	int i, rc;
+	int rc;
 
 	if (tty3270_max_index < index + 1)
 		tty3270_max_index = index + 1;
@@ -1186,8 +1068,7 @@ tty3270_create_view(int index, struct tty3270 **newtp)
 	tty3270_create_prompt(tp);
 
 	/* Create blank line for every line in the tty output area. */
-	for (i = 0; i < tty3270_tty_rows(tp); i++)
-		tty3270_blank_line(tp);
+	tty3270_blank_screen(tp);
 
 	tp->kbd->port = &tp->port;
 	tp->kbd->fn_handler[KVAL(K_INCRCONSOLE)] = tty3270_exit_tty;
@@ -1298,7 +1179,7 @@ static void tty3270_put_character(struct tty3270 *tp, char ch)
 	struct tty3270_line *line;
 	struct tty3270_cell *cell;
 
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 	if (line->len <= tp->cx) {
 		while (line->len < tp->cx) {
 			cell = line->cells + line->len;
@@ -1311,6 +1192,7 @@ static void tty3270_put_character(struct tty3270 *tp, char ch)
 	cell = line->cells + tp->cx;
 	cell->character = ch;
 	cell->attributes = tp->attributes;
+	line->dirty = 1;
 }
 
 /*
@@ -1326,30 +1208,27 @@ static void tty3270_cr(struct tty3270 *tp)
  */
 static void tty3270_lf(struct tty3270 *tp)
 {
-	struct tty3270_line temp;
+	struct tty3270_line *line;
 	int i;
 
-	tty3270_convert_line(tp, tp->cy);
 	if (tp->cy < tty3270_tty_rows(tp) - 1) {
 		tp->cy++;
-		return;
+	} else {
+		tp->line_view_start = tty3270_line_increment(tp, tp->line_view_start, 1);
+		tp->line_write_start = tty3270_line_increment(tp, tp->line_write_start, 1);
+		for (i = 0; i < tty3270_tty_rows(tp); i++)
+			tty3270_get_view_line(tp, i)->dirty = 1;
 	}
-	/* Last line just filled up. Add new, blank line. */
-	tty3270_blank_line(tp);
-	temp = tp->screen[0];
-	temp.len = 0;
-	for (i = 0; i < tty3270_tty_rows(tp) - 1; i++)
-		tp->screen[i] = tp->screen[i+1];
-	tp->screen[tty3270_tty_rows(tp) - 1] = temp;
-	tty3270_rebuild_update(tp);
+
+	line = tty3270_get_write_line(tp, tp->cy);
+	line->len = 0;
+	line->dirty = 1;
 }
 
 static void tty3270_ri(struct tty3270 *tp)
 {
-	if (tp->cy > 0) {
-	    tty3270_convert_line(tp, tp->cy);
-	    tp->cy--;
-	}
+	if (tp->cy > 0)
+		tp->cy--;
 }
 
 static void tty3270_reset_cell(struct tty3270 *tp, struct tty3270_cell *cell)
@@ -1366,7 +1245,7 @@ static void tty3270_insert_characters(struct tty3270 *tp, int n)
 	struct tty3270_line *line;
 	int k;
 
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 	while (line->len < tp->cx)
 		tty3270_reset_cell(tp, &line->cells[line->len++]);
 	if (n > tp->view.cols - tp->cx)
@@ -1391,7 +1270,7 @@ static void tty3270_delete_characters(struct tty3270 *tp, int n)
 	struct tty3270_line *line;
 	int i;
 
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 	if (line->len <= tp->cx)
 		return;
 	if (line->len - tp->cx <= n) {
@@ -1411,7 +1290,7 @@ static void tty3270_erase_characters(struct tty3270 *tp, int n)
 	struct tty3270_line *line;
 	struct tty3270_cell *cell;
 
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 	while (line->len > tp->cx && n-- > 0) {
 		cell = line->cells + tp->cx++;
 		tty3270_reset_cell(tp, cell);
@@ -1432,7 +1311,7 @@ static void tty3270_erase_line(struct tty3270 *tp, int mode)
 	struct tty3270_cell *cell;
 	int i, start, end;
 
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 
 	switch (mode) {
 	case 0:
@@ -1459,8 +1338,6 @@ static void tty3270_erase_line(struct tty3270 *tp, int mode)
 
 	if (line->len <= end)
 		line->len = end;
-
-	tty3270_convert_line(tp, tp->cy);
 }
 
 /*
@@ -1471,6 +1348,7 @@ static void tty3270_erase_line(struct tty3270 *tp, int mode)
  */
 static void tty3270_erase_display(struct tty3270 *tp, int mode)
 {
+	struct tty3270_line *line;
 	int i, start, end;
 
 	switch (mode) {
@@ -1492,10 +1370,10 @@ static void tty3270_erase_display(struct tty3270 *tp, int mode)
 		return;
 	}
 	for (i = start; i < end; i++) {
-		tp->screen[i].len = 0;
-		tty3270_convert_line(tp, i);
+		line = tty3270_get_write_line(tp, i);
+		line->len = 0;
+		line->dirty = 1;
 	}
-	tty3270_rebuild_update(tp);
 }
 
 /*
@@ -1579,19 +1457,14 @@ static void tty3270_goto_xy(struct tty3270 *tp, int cx, int cy)
 	int max_cy = max(0, cy);
 
 	tp->cx = min_t(int, tp->view.cols - 1, max_cx);
-	line = tp->screen + tp->cy;
+	line = tty3270_get_write_line(tp, tp->cy);
 	while (line->len < tp->cx) {
 		cell = line->cells + line->len;
 		cell->character = ' ';
 		cell->attributes = tp->attributes;
 		line->len++;
 	}
-
-	cy = min_t(int, tty3270_tty_rows(tp) - 1, max_cy);
-	if (cy != tp->cy) {
-		tty3270_convert_line(tp, tp->cy);
-		tp->cy = cy;
-	}
+	tp->cy = min_t(int, tty3270_tty_rows(tp) - 1, max_cy);
 }
 
 /*
@@ -1652,7 +1525,6 @@ static void tty3270_escape_sequence(struct tty3270 *tp, char ch)
 			tp->saved_attributes = tp->attributes;
 			break;
 		case '8':		/* Restore cursor position. */
-			tty3270_convert_line(tp, tp->cy);
 			tty3270_goto_xy(tp, tp->saved_cx, tp->saved_cy);
 			tp->attributes = tp->saved_attributes;
 			break;
@@ -1767,7 +1639,6 @@ static void tty3270_escape_sequence(struct tty3270 *tp, char ch)
 		tp->saved_attributes = tp->attributes;
 		break;
 	case 'u':	/* Restore cursor position. */
-		tty3270_convert_line(tp, tp->cy);
 		tty3270_goto_xy(tp, tp->saved_cx, tp->saved_cy);
 		tp->attributes = tp->saved_attributes;
 		break;
@@ -1843,9 +1714,6 @@ static void tty3270_do_write(struct tty3270 *tp, struct tty_struct *tty,
 			break;
 		}
 	}
-	/* Convert current line to 3270 data fragment. */
-	tty3270_convert_line(tp, tp->cy);
-
 	/* Setup timer to update display after 1/10 second */
 	if (!timer_pending(&tp->timer))
 		tty3270_set_timer(tp, HZ/10);
@@ -1970,8 +1838,6 @@ static void tty3270_hangup(struct tty_struct *tty)
 	tty3270_reset_attributes(&tp->attributes);
 	tty3270_reset_attributes(&tp->saved_attributes);
 	tty3270_blank_screen(tp);
-	while (tp->nr_lines < tty3270_tty_rows(tp))
-		tty3270_blank_line(tp);
 	tp->update_flags = TTY_UPDATE_ALL;
 	spin_unlock_irq(&tp->view.lock);
 	tty3270_set_timer(tp, 1);
diff --git a/drivers/s390/char/raw3270.h b/drivers/s390/char/raw3270.h
index 23efa6b8be49..5ca1af6df935 100644
--- a/drivers/s390/char/raw3270.h
+++ b/drivers/s390/char/raw3270.h
@@ -219,7 +219,6 @@ void raw3270_unregister_notifier(struct raw3270_notifier *);
 struct string
 {
 	struct list_head list;
-	struct list_head update;
 	unsigned long size;
 	unsigned long len;
 	char string[];
@@ -245,7 +244,6 @@ alloc_string(struct list_head *free_list, unsigned long len)
 			list_del(&cs->list);
 		cs->len = len;
 		INIT_LIST_HEAD(&cs->list);
-		INIT_LIST_HEAD(&cs->update);
 		return cs;
 	}
 	return NULL;