From: Arnd Bergmann Date: Tue, 20 Jun 2017 21:10:42 +0000 (+0200) Subject: tty: improve tty_insert_flip_char() slow path X-Git-Tag: C0P2-H0.0--20200415~7467 X-Git-Url: https://git.somdevices.com/?a=commitdiff_plain;h=750462424193bfa48155c26e0186f2bb5a4485e2;p=linux.git tty: improve tty_insert_flip_char() slow path commit 065ea0a7afd64d6cf3464bdd1d8cd227527e2045 upstream. While working on improving the fast path of tty_insert_flip_char(), I noticed that by calling tty_buffer_request_room(), we needlessly move to the separate flag buffer mode for the tty, even when all characters use TTY_NORMAL as the flag. This changes the code to call __tty_buffer_request_room() with the correct flag, which will then allocate a regular buffer when it rounds out of space but no special flags have been used. I'm guessing that this is the behavior that Peter Hurley intended when he introduced the compacted flip buffers. Fixes: acc0f67f307f ("tty: Halve flip buffer GFP_ATOMIC memory consumption") Cc: Peter Hurley Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 013693b59c29..6b1dc32cfa22 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -375,10 +375,11 @@ int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag) struct tty_buffer *tb = port->buf.tail; int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; - if (!tty_buffer_request_room(port, 1)) + if (!__tty_buffer_request_room(port, 1, flags)) return 0; - *flag_buf_ptr(tb, tb->used) = flag; + if (~tb->flags & TTYB_NORMAL) + *flag_buf_ptr(tb, tb->used) = flag; *char_buf_ptr(tb, tb->used++) = ch; return 1;