From: Linus Torvalds torvalds@linux-foundation.org
commit d7fe75cbc23c7d225eee2ef04def239b6603dce7 upstream.
The ICANON case is a bit messy, since it has to look for the line ending, and has special code to then suppress line ending characters if they match the __DISABLED_CHAR. So it actually looks up the line ending even past the point where it knows it won't copy it to the result buffer.
That said, apart from all those odd legacy N_TTY ICANON cases, the actual "should we continue copying" logic isn't really all that complicated or different from the non-canon case. In fact, the lack of "wait for at least N characters" arguably makes the repeat case slightly simpler. It really just boils down to "there's more of the line to be copied".
So add the necessarily trivial logic, and now the N_TTY case will give long result lines even when in canon mode.
Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/n_tty.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-)
--- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2011,21 +2011,22 @@ static bool copy_from_read_buf(struct tt * read_tail published */
-static void canon_copy_from_read_buf(struct tty_struct *tty, +static bool canon_copy_from_read_buf(struct tty_struct *tty, unsigned char **kbp, size_t *nr) { struct n_tty_data *ldata = tty->disc_data; size_t n, size, more, c; size_t eol; - size_t tail; + size_t tail, canon_head; int found = 0;
/* N.B. avoid overrun if nr == 0 */ if (!*nr) - return; + return false;
- n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail); + canon_head = smp_load_acquire(&ldata->canon_head); + n = min(*nr + 1, canon_head - ldata->read_tail);
tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1); size = min_t(size_t, tail + n, N_TTY_BUF_SIZE); @@ -2069,7 +2070,11 @@ static void canon_copy_from_read_buf(str else ldata->push = 0; tty_audit_push(); + return false; } + + /* No EOL found - do a continuation retry if there is more data */ + return ldata->read_tail != canon_head; }
/** @@ -2140,8 +2145,13 @@ static ssize_t n_tty_read(struct tty_str * termios_rwsem, and can just continue to copy data. */ if (*cookie) { - if (copy_from_read_buf(tty, &kb, &nr)) - return kb - kbuf; + if (ldata->icanon && !L_EXTPROC(tty)) { + if (canon_copy_from_read_buf(tty, &kb, &nr)) + return kb - kbuf; + } else { + if (copy_from_read_buf(tty, &kb, &nr)) + return kb - kbuf; + }
/* No more data - release locks and stop retries */ n_tty_kick_worker(tty); @@ -2238,7 +2248,8 @@ static ssize_t n_tty_read(struct tty_str }
if (ldata->icanon && !L_EXTPROC(tty)) { - canon_copy_from_read_buf(tty, &kb, &nr); + if (canon_copy_from_read_buf(tty, &kb, &nr)) + goto more_to_be_read; } else { /* Deal with packet mode. */ if (packet && kb == kbuf) { @@ -2256,6 +2267,7 @@ static ssize_t n_tty_read(struct tty_str * will release them when done. */ if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) { +more_to_be_read: remove_wait_queue(&tty->read_wait, &wait); *cookie = cookie; return kb - kbuf;