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n_tty: Line copy to user buffer in canonical mode

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Instead of pushing one char per loop, pre-compute the data length
to copy and copy all at once.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-06-15 09:14:17 -04:00 committed by Greg Kroah-Hartman
parent 88bb0de389
commit 32f13521ca
1 changed files with 76 additions and 32 deletions
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108
drivers/tty/n_tty.c
View file

@ -74,6 +74,13 @@
#define ECHO_OP_SET_CANON_COL 0x81
#define ECHO_OP_ERASE_TAB 0x82
#undef N_TTY_TRACE
#ifdef N_TTY_TRACE
# define n_tty_trace(f, args...) trace_printk(f, ##args)
#else
# define n_tty_trace(f, args...)
#endif
struct n_tty_data {
unsigned int column;
unsigned long overrun_time;
@ -1748,58 +1755,95 @@ static int copy_from_read_buf(struct tty_struct *tty,
}
/**
* canon_copy_to_user - copy read data in canonical mode
* canon_copy_from_read_buf - copy read data in canonical mode
* @tty: terminal device
* @b: user data
* @nr: size of data
*
* Helper function for n_tty_read. It is only called when ICANON is on;
* it copies characters one at a time from the read buffer to the user
* space buffer.
* it copies one line of input up to and including the line-delimiting
* character into the user-space buffer.
*
* Called under the atomic_read_lock mutex
*/
static int canon_copy_to_user(struct tty_struct *tty,
unsigned char __user **b,
size_t *nr)
static int canon_copy_from_read_buf(struct tty_struct *tty,
unsigned char __user **b,
size_t *nr)
{
struct n_tty_data *ldata = tty->disc_data;
unsigned long flags;
int eol, c;
size_t n, size, more, c;
unsigned long eol;
int ret, tail, found = 0;
/* N.B. avoid overrun if nr == 0 */
raw_spin_lock_irqsave(&ldata->read_lock, flags);
while (*nr && ldata->read_cnt) {
eol = test_and_clear_bit(ldata->read_tail, ldata->read_flags);
c = ldata->read_buf[ldata->read_tail];
ldata->read_tail = (ldata->read_tail+1) & (N_TTY_BUF_SIZE-1);
ldata->read_cnt--;
if (eol) {
/* this test should be redundant:
* we shouldn't be reading data if
* canon_data is 0
*/
if (--ldata->canon_data < 0)
ldata->canon_data = 0;
}
n = min_t(size_t, *nr, ldata->read_cnt);
if (!n) {
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
return 0;
}
if (!eol || (c != __DISABLED_CHAR)) {
if (tty_put_user(tty, c, *b))
return -EFAULT;
*b += 1;
*nr -= 1;
}
if (eol) {
tty_audit_push(tty);
return 0;
}
raw_spin_lock_irqsave(&ldata->read_lock, flags);
tail = ldata->read_tail;
size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
n_tty_trace("%s: nr:%zu tail:%d n:%zu size:%zu\n",
__func__, *nr, tail, n, size);
eol = find_next_bit(ldata->read_flags, size, tail);
more = n - (size - tail);
if (eol == N_TTY_BUF_SIZE && more) {
/* scan wrapped without finding set bit */
eol = find_next_bit(ldata->read_flags, more, 0);
if (eol != more)
found = 1;
} else if (eol != size)
found = 1;
size = N_TTY_BUF_SIZE - tail;
n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
c = n;
if (found && ldata->read_buf[eol] == __DISABLED_CHAR)
n--;
n_tty_trace("%s: eol:%lu found:%d n:%zu c:%zu size:%zu more:%zu\n",
__func__, eol, found, n, c, size, more);
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
if (n > size) {
ret = copy_to_user(*b, &ldata->read_buf[tail], size);
if (ret)
return -EFAULT;
ret = copy_to_user(*b + size, ldata->read_buf, n - size);
} else
ret = copy_to_user(*b, &ldata->read_buf[tail], n);
if (ret)
return -EFAULT;
*b += n;
*nr -= n;
raw_spin_lock_irqsave(&ldata->read_lock, flags);
ldata->read_tail = (ldata->read_tail + c) & (N_TTY_BUF_SIZE - 1);
ldata->read_cnt -= c;
if (found) {
__clear_bit(eol, ldata->read_flags);
/* this test should be redundant:
* we shouldn't be reading data if
* canon_data is 0
*/
if (--ldata->canon_data < 0)
ldata->canon_data = 0;
}
raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
if (found)
tty_audit_push(tty);
return 0;
}
@ -1972,7 +2016,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
}
if (ldata->icanon && !L_EXTPROC(tty)) {
retval = canon_copy_to_user(tty, &b, &nr);
retval = canon_copy_from_read_buf(tty, &b, &nr);
if (retval)
break;
} else {