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Subject[PATCH v3 6/9] n_tty: Remove overflow tests from receive_buf() path
Date
Always pre-figure the space available in the read_buf and limit
the inbound receive request to that amount.

For compatibility reasons with the non-flow-controlled interface,
n_tty_receive_buf() will continue filling read_buf until all data
has been received or receive_room() returns 0.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/n_tty.c | 85 +++++++++++++++++++++++------------------------------
1 file changed, 37 insertions(+), 48 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index aed1e94..0f33e0c 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -315,12 +315,9 @@ static inline void n_tty_check_unthrottle(struct tty_struct *tty)
* not active.
*/

-static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
+static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
{
- if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
- *read_buf_addr(ldata, ldata->read_head) = c;
- ldata->read_head++;
- }
+ *read_buf_addr(ldata, ldata->read_head++) = c;
}

/**
@@ -1332,11 +1329,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
return;
}
if (c == '\n') {
- if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
- if (L_ECHO(tty))
- process_output('\a', tty);
- return;
- }
if (L_ECHO(tty) || L_ECHONL(tty)) {
echo_char_raw('\n', ldata);
commit_echoes(tty);
@@ -1344,8 +1336,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
goto handle_newline;
}
if (c == EOF_CHAR(tty)) {
- if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
- return;
c = __DISABLED_CHAR;
goto handle_newline;
}
@@ -1353,11 +1343,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
(c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
? 1 : 0;
- if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
- if (L_ECHO(tty))
- process_output('\a', tty);
- return;
- }
/*
* XXX are EOL_CHAR and EOL2_CHAR echoed?!?
*/
@@ -1387,12 +1372,6 @@ handle_newline:
}

parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
- if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
- /* beep if no space */
- if (L_ECHO(tty))
- process_output('\a', tty);
- return;
- }
if (L_ECHO(tty)) {
finish_erasing(ldata);
if (c == '\n')
@@ -1431,14 +1410,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
start_tty(tty);
process_echoes(tty);
}
-
- parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
- if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
- /* beep if no space */
- if (L_ECHO(tty))
- process_output('\a', tty);
- return;
- }
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
@@ -1447,6 +1418,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
echo_char(c, tty);
commit_echoes(tty);
}
+ parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
if (parmrk)
put_tty_queue(c, ldata);
put_tty_queue(c, ldata);
@@ -1475,13 +1447,6 @@ n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
start_tty(tty);
process_echoes(tty);
}
-
- if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - 1)) {
- /* beep if no space */
- if (L_ECHO(tty))
- process_output('\a', tty);
- return;
- }
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
@@ -1690,8 +1655,23 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
char *fp, int count)
{
+ int room, n;
+
down_read(&tty->termios_rwsem);
- __receive_buf(tty, cp, fp, count);
+
+ while (1) {
+ room = receive_room(tty);
+ n = min(count, room);
+ if (!n)
+ break;
+ __receive_buf(tty, cp, fp, n);
+ cp += n;
+ if (fp)
+ fp += n;
+ count -= n;
+ }
+
+ tty->receive_room = room;
n_tty_check_throttle(tty);
up_read(&tty->termios_rwsem);
}
@@ -1700,22 +1680,31 @@ static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
char *fp, int count)
{
struct n_tty_data *ldata = tty->disc_data;
- int room;
+ int room, n, rcvd = 0;

down_read(&tty->termios_rwsem);

- tty->receive_room = room = receive_room(tty);
- if (!room)
- ldata->no_room = 1;
- count = min(count, room);
- if (count) {
- __receive_buf(tty, cp, fp, count);
- n_tty_check_throttle(tty);
+ while (1) {
+ room = receive_room(tty);
+ n = min(count, room);
+ if (!n) {
+ if (!room)
+ ldata->no_room = 1;
+ break;
+ }
+ __receive_buf(tty, cp, fp, n);
+ cp += n;
+ if (fp)
+ fp += n;
+ count -= n;
+ rcvd += n;
}

+ tty->receive_room = room;
+ n_tty_check_throttle(tty);
up_read(&tty->termios_rwsem);

- return count;
+ return rcvd;
}

int is_ignored(int sig)
--
1.8.1.2


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