linux-kernel - Re: [PATCH 05/32] timerfd/timens: Take into account ns clock offsets

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Date:   Wed, 6 Feb 2019 22:38:31 -0800
From:   Andrei Vagin <avagin@...il.com>
To:     Cyrill Gorcunov <gorcunov@...il.com>
Cc:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org,
        Adrian Reber <adrian@...as.de>,
        Andrei Vagin <avagin@...nvz.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andy Tucker <agtucker@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jeff Dike <jdike@...toit.com>, Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 05/32] timerfd/timens: Take into account ns clock offsets

On Wed, Feb 06, 2019 at 11:52:03AM +0300, Cyrill Gorcunov wrote:
> On Wed, Feb 06, 2019 at 12:10:39AM +0000, Dmitry Safonov wrote:
> > From: Andrei Vagin <avagin@...il.com>
> > 
> > Make timerfd respect timens offsets.
> > Provide two helpers timens_clock_to_host() timens_clock_from_host() that
> > are useful to wire up timens to different kernel subsystems.
> > Following patches will use timens_clock_from_host(), added here for
> > completeness.
> > 
> > Signed-off-by: Andrei Vagin <avagin@...nvz.org>
> > Co-developed-by: Dmitry Safonov <dima@...sta.com>
> > Signed-off-by: Dmitry Safonov <dima@...sta.com>
> > ---
> >  fs/timerfd.c | 16 +++++++++++-----
> >  1 file changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/timerfd.c b/fs/timerfd.c
> > index 803ca070d42e..c7ae1e371912 100644
> > --- a/fs/timerfd.c
> > +++ b/fs/timerfd.c
> > @@ -26,6 +26,7 @@
> >  #include <linux/syscalls.h>
> >  #include <linux/compat.h>
> >  #include <linux/rcupdate.h>
> > +#include <linux/time_namespace.h>
> >  
> >  struct timerfd_ctx {
> >  	union {
> > @@ -433,22 +434,27 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
> >  }
> >  
> >  static int do_timerfd_settime(int ufd, int flags, 
> > -		const struct itimerspec64 *new,
> > +		struct itimerspec64 *new,
> >  		struct itimerspec64 *old)
> >  {
> >  	struct fd f;
> >  	struct timerfd_ctx *ctx;
> >  	int ret;
> >  
> > -	if ((flags & ~TFD_SETTIME_FLAGS) ||
> > -		 !itimerspec64_valid(new))
> > -		return -EINVAL;
> 
> Please don't defer this early test of a @flags value. Otherwise
> if @flags is invalid you continue fget/put/clock-to-host even
> if result will be dropped out then.

Cyrill, you are right. I moved this check together with
itimerspec64_valid(). The idea was to call itimerspec64_valid() after
applying clock offsets but for that, we need to know clockid.

Let's wait a bit for other comments to this patch set and then we will
fix all things what will be found.

Thanks,
Andrei