linux-kernel - Re: [ 02/42] TTY: do not update atime/mtime on read/write

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Message-ID: <CA+55aFzfxMvWVRjqV4pzz7XtpDGbxwGumGVeRT7OsF95noG4xw@mail.gmail.com>
Date:	Tue, 30 Apr 2013 18:41:44 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Simon Kirby <sim@...tway.ca>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [ 02/42] TTY: do not update atime/mtime on read/write

On Tue, Apr 30, 2013 at 5:57 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Patch is whitespace-damaged and totally untested! Caveat applicator.

Ok, so it's still whitespace-damaged, but it seems to work. The
appended has the "8 second rule" too..

Comments? Simon?

           Linus

--- snip snip ---
 drivers/tty/pty.c    | 3 +++
 drivers/tty/tty_io.c | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index a62798fcc014..59bfaecc4e14 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -681,6 +681,9 @@ static int ptmx_open(struct inode *inode, struct file *filp)

        nonseekable_open(inode, filp);

+       /* We refuse fsnotify events on ptmx, since it's a shared resource */
+       filp->f_mode |= FMODE_NONOTIFY;
+
        retval = tty_alloc_file(filp);
        if (retval)
                return retval;
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 97ebc8c5864e..6464029e4860 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -988,10 +988,10 @@ void start_tty(struct tty_struct *tty)

 EXPORT_SYMBOL(start_tty);

+/* We limit tty time update visibility to every 8 seconds or so. */
 static void tty_update_time(struct timespec *time)
 {
-       unsigned long sec = get_seconds();
-       sec -= sec % 60;
+       unsigned long sec = get_seconds() & ~7;
        if ((long)(sec - time->tv_sec) > 0)
                time->tv_sec = sec;
 }
--
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